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Background and Purpose: Although exogenous nitric oxide (NO) clearly modifies platelet function, the role and the source of endogenous NO in vivo remain undefined. In addition, endothelial NO synthase (NOS-3) critically regulates vessel tone but its role in modulating platelet function is unclear. In this paper we have investigated the roles of endogenous NO and NOS-3 in regulating platelet function in vivo and determined the functional contribution made by platelet-derived NO.Experimental Approach: We used a mouse model for directly assessing platelet functional responses in situ in the presence of an intact vascular endothelium with supporting in vitro and molecular studies.Key Results: Acute NOS inhibition by N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME) enhanced platelet aggregatory responses to thrombin and platelets were shown to be regulated primarily by NO sources external to the platelet. Elevation of endogenous NOS inhibitors to mimic effects reported in patients with cardiovascular diseases did not enhance platelet responses. Platelet responsiveness following agonist stimulation was not modified in male or female NOS-3(-/-) mice but responses in NOS-3(-/-) mice were enhanced by L-NAME.Conclusions and Implications: Platelets are regulated by endogenous NO in vivo, primarily by NO originating from the environment external to the platelet with a negligible or undetectable role of platelet-derived NO. Raised levels of endogenous NOS inhibitors, as reported in a range of diseases were not, in isolation, sufficient to enhance platelet activity and NOS-3 is not essential for normal platelet function in vivo due to the presence of bioactive NO following deletion of NOS-3. [ABSTRACT FROM AUTHOR]

As the opioid crisis has continued to grow, so has the number of infants exposed to opioids during the prenatal period. A growing concern is that prenatal exposure to opioids may induce persistent neurological changes that increase the propensity for future addictions. Although alcohol represents the most likely addictive substance that the growing population of prenatal opioid exposed will encounter as they mature, no studies to date have examined the effect of prenatal opioid exposure on future sensitivity to alcohol reward. Using a recently developed mouse model of prenatal methadone exposure (PME), we investigated the rewarding properties of alcohol and alcohol consumption in male and female adolescent PME and prenatal saline exposed (PSE) control animals. Conditioned place preference to alcohol was disrupted in PME offspring in a sex-dependent manner with PME males exhibiting resistance to the rewarding properties of alcohol. Repeated injections of alcohol revealed enhanced sensitivity to the locomotor-stimulating effects of alcohol specific to PME females. PME males consumed significantly more alcohol over 4 weeks of alcohol access relative to PSE males and exhibited increased resistance to quinine-adulterated alcohol. Further, a novel machine learning model was developed to employ measured differences in alcohol consumption and drinking microstructure to reliably predict prenatal exposure. These findings indicate that PME alters the sensitivity to alcohol reward in adolescent mice in a sex-specific manner and suggests prenatal opioid exposure may induce persistent effects on reward neurocircuitry that can reprogram offspring behavioural response to alcohol later in life. [ABSTRACT FROM AUTHOR]

Background and Purpose: Maternal infections are one of the main causes of adverse developmental outcomes including embryonic resorption and preterm labour. In this study a mouse model of inflammation-associated preterm delivery was developed, and used to study the relationship between nitric oxide (NO) and prostaglandins (PGs).Experimental Approach: The murine model of preterm labour was achieved by assaying different doses of bacterial lipopolysaccharides (LPS). Once established, it was used to analyse uterine levels of prostaglandins E(2) and F(2α) (by radioimmunoassay), cyclooxygenases (COX) and NOS proteins (by Western blot) and NO synthase (NOS) activity. Effects of inhibitors of COX and NOS on LPS-induced preterm labour were also studied. In vitro assays with a nitric oxide donor (SNAP) were performed to analyse the modulation of prostaglandin production by NO.Key Results: Lipopolysaccharide increased uterine NO and PG synthesis and induced preterm delivery. Co-administration of meloxicam, a cyclooxygenase-2 inhibitor, or aminoguanidine, an inducible NOS inhibitor, prevented LPS-induced preterm delivery and blocked the increase in PGs and NO. Notably, the levels of NO were found to determine its effect on PG synthesis; low concentrations of NO reduced PG synthesis whereas high concentrations augmented them.Conclusions and Implications: An infection-associated model of preterm labour showed that preterm delivery can be prevented by decreasing PG or NO production. NO was found to have a dual effect on PG synthesis depending on its concentration. These data contribute to the understanding of the interaction between NO and PGs in pregnancy and parturition, and could help to improve neonatal outcomes. [ABSTRACT FROM AUTHOR]

Background and Purpose: The serine and cysteine peptidase inhibitor, BbCI, isolated from Bauhinia bauhinioides seeds, is similar to the classical plant Kunitz inhibitor, STI, but lacks disulphide bridges and methionine residues. BbCI blocks activity of the serine peptidases, elastase (K(iapp) 5.3 nM) and cathepsin G (K(iapp) 160.0 nM), and the cysteine peptidase cathepsin L (K(iapp) 0.2 nM). These three peptidases play important roles in the inflammatory process.Experimental Approach: We measured the effects of BbCI on paw oedema and on leucocyte accumulation in pleurisy, both induced by carrageenan. Leucocyte-endothelial cell interactions in scrotal microvasculature in Wistar rats were investigated using intravital microscopy. Cytokine levels in pleural exudate and serum were measured by elisa.Key Results: Pretreatment of the animals with BbCI (2.5 mg·kg(-1)), 30 min before carrageenan-induced inflammation, effectively reduced paw oedema and bradykinin release, neutrophil migration into the pleural cavity. The number of rolling, adhered and migrated leucocytes at the spermatic fascia microcirculation following carrageenan injection into the scrotum were reduced by BbCI pretreatment. Furthermore, levels of the rat chemokine cytokine-induced neutrophil chemo-attractant-1 were significantly reduced in both pleural exudates and serum from animals pretreated with BbCI. Levels of interleukin-1β or tumour necrosis factor-α, however, did not change.Conclusions and Implications: Taken together, our data suggest that the anti-inflammatory properties of BbCI may be useful in investigations of other pathological processes in which human neutrophil elastase, cathepsin G and cathepsin L play important roles. [ABSTRACT FROM AUTHOR]

Background and Purpose: Insulin-induced Na(+) retention in the distal nephron may contribute to the development of oedema/hypertension in patients with type 2 diabetes. This response to insulin is usually attributed to phosphatidylinositol-3-kinase (PI3K)/serum and glucocorticoid-inducible kinase 1 (SGK1) but a role for protein kinase B (PKB) has been proposed. The present study therefore aimed to clarify the way in which insulin can evoke Na(+) retention.Experimental Approach: We examined the effects of nominally selective inhibitors of PI3K (wortmannin, PI103, GDC-0941), SGK1 (GSK650394A) and PKB (Akti-1/2) on Na(+) transport in hormone-deprived and insulin-stimulated cortical collecting duct (mpkCCD) cells, while PI3K, SGK1 and PKB activities were assayed by monitoring the phosphorylation of endogenous proteins.Key Results: Wortmannin substantially inhibited basal Na(+) transport whereas PI103 and GDC-0941 had only very small effects. However, these PI3K inhibitors all abolished insulin-induced Na(+) absorption and inactivated PI3K, SGK1 and PKB fully. GSK650394A and Akti-1/2 also inhibited insulin-evoked Na(+) absorption and while GSK650394A inhibited SGK1 without affecting PKB, Akti-1/2 inactivated both kinases.Conclusion and Implications: While studies undertaken using PI103 and GDC-0941 show that hormone-deprived cells can absorb Na(+) independently of PI3K, PI3K seems to be essential for insulin induced Na(+) transport. Akti-1/2 does not act as a selective inhibitor of PKB and data obtained using this compound must therefore be treated with caution. GSK650394A, on the other hand, selectively inhibits SGK1 and the finding that GSK650394A suppressed insulin-induced Na(+) absorption suggests that this response is dependent upon signalling via PI3K/SGK1. [ABSTRACT FROM AUTHOR]

Background and Purpose: The 5-HT(4) receptor may be a target for antidepressant drugs. Here we have examined the effects of the dual antidepressant, venlafaxine, on 5-HT(4) receptor-mediated signalling events.Experimental Approach: The effects of 21 days treatment (p.o.) with high (40 mg·kg(-1)) and low (10 mg·kg(-1)) doses of venlafaxine, were evaluated at different levels of 5-HT(4) receptor-mediated neurotransmission by using in situ hybridization, receptor autoradiography, adenylate cyclase assays and electrophysiological recordings in rat brain. The selective noradrenaline reuptake inhibitor, reboxetine (10 mg·kg(-1), 21 days) was also evaluated on 5-HT(4) receptor density.Key Results: Treatment with a high dose (40 mg·kg(-1)) of venlafaxine did not alter 5-HT(4) mRNA expression, but decreased the density of 5-HT(4) receptors in caudate-putamen (% reduction = 26 ± 6), hippocampus (% reduction = 39 ± 7 and 39 ± 8 for CA1 and CA3 respectively) and substantia nigra (% reduction = 49 ± 5). Zacopride-stimulated adenylate cyclase activation was unaltered following low-dose treatment (10 mg·kg(-1)) while it was attenuated in rats treated with 40 mg·kg(-1) of venlafaxine (% reduction = 51 ± 2). Furthermore, the amplitude of population spike in pyramidal cells of CA1 of hippocampus induced by zacopride was significantly attenuated in rats receiving either dose of venlafaxine. Chronic reboxetine did not modify 5-HT(4) receptor density.Conclusions and Implications: Our data indicate a functional desensitization of 5-HT(4) receptors after chronic venlafaxine, similar to that observed after treatment with the classical selective inhibitors of 5-HT reuptake. [ABSTRACT FROM AUTHOR]

Background and Purpose: Andrographolide is a diterpenoid lactone isolated from a traditional medicinal herb, Andrographis paniculata. It possesses potent anti-inflammatory activity. The present study examined potential therapeutic effects of andrographolide on cerebral ischaemia using a rat model with permanent middle cerebral artery occlusion (pMCAO).Experimental Approach: The MCA in rats was permanently occluded (by cautery), and 24 h later neurological effects were assessed with behavioural scores. Infarct volume and microglial activation were determined histologically. The p65 form of the transcription factor, nuclear factor-κB (NF-κB), was measured by Western blot, and cytokines by immunoassay of brain extracts.Key Results: Andrographolide, given i.p. 1 h after pMCAO, reduced infarct volume with a maximum reduction of approximately 50% obtained at 0.1 mg·kg(-1). Neurological deficits were also reduced by andrographolide, reflecting a correlation between infarct volume and neurological deficits. pMCAO was found to induce activation of microglia and elevate tumour necrosis factor (TNF)-α, interleukin (IL)-1β and prostaglandin (PG)E(2) in the ischaemic brain areas. Andrographolide (0.1 mg·kg(-1)) significantly attenuated or abolished these effects. In addition, andrographolide suppressed the translocation of p65 from cytosol to nucleus, indicating reduced NF-κB activation.Conclusions and Implications: Andrographolide exhibited neuroprotective effects, with accompanying suppression of NF-κB and microglial activation, and reduction in the production of cytokines including TNF-α and IL-1β, and pro-inflammatory factors such as PGE(2). Our findings suggest that andrographolide may have therapeutic value in the treatment of stroke. [ABSTRACT FROM AUTHOR]

Background and Purpose: K(v)11.1 channels are involved in regulating cellular excitability in various tissues including brain, heart and smooth muscle. In these tissues, at least two isoforms, K(v)11.1a and K(v)11.1b, with different kinetics, are expressed. K(v)11.1 activators are potential therapeutic agents, but their effects have only been tested on the K(v)11.1a isoform. In this study, the effects of two different K(v)11.1 activators, NS1643 and RPR260243, were characterized on K(v)11.1a and K(v)11.1b channels.Experimental Approach: K(v)11.1a and K(v)11.1b channels were expressed in Xenopus laevis oocytes, and currents were measured using two-electrode voltage clamp. I/V curves and channel kinetics were measured before and after application of 30 µM NS1643 or 10 µM RPR260243.Key Results: NS1643 increased steady-state currents through Kv11.1b several fold more than through K(v)11.1a channels, without affecting EC(50) values. NS1643 increased activation rates and decreased rates of inactivation, recovery from inactivation and deactivation for both channels. Except for activation, where effect of NS1643 was comparable, relative changes were greater for Kv11.1b than for K(v)11.1a. RPR260243 increased steady-state currents only through Kv11.1a channels, but slowed the process of deactivation for both channels primarily by decreasing time constant of slow deactivation. This effect was greater on K(v)11.1b than on K(v)11.1a. Effects of both compounds on heteromeric K(v)11.1a/K(v)11.1b channels were similar to those on K(v)11.1a.Conclusions and Implications: Both NS1643 and RPR260243 displayed differential effects on K(v)11.1a and K(v)11.1b channels, the effects being relatively more pronounced on K(v)11.1b channels. This affirms the importance of testing the effect of K(v)11.1 activators on different channel isoforms. [ABSTRACT FROM AUTHOR]

Background and Purpose: Cannabinoid CB(1) receptor antagonists reduce food intake and body weight, but clinical use in humans is limited by effects on the CNS. We have evaluated a novel cannabinoid antagonist (AM6545) designed to have limited CNS penetration, to see if it would inhibit food intake in rodents, without aversive effects.Experimental Approach: Cannabinoid receptor binding studies, cAMP assays, brain penetration studies and gastrointestinal motility studies were carried out to assess the activity profile of AM6545. The potential for AM6545 to induce malaise in rats and the actions of AM6545 on food intake and body weight were also investigated.Key Results: AM6545 binds to CB(1) receptors with a K(i) of 1.7 nM and CB(2) receptors with a K(i) of 523 nM. AM6545 is a neutral antagonist, having no effect on cAMP levels in transfected cells and was less centrally penetrant than AM4113, a comparable CB(1) receptor antagonist. AM6545 reversed the effects of WIN55212-2 in an assay of colonic motility. In contrast to AM251, AM6545 did not produce conditioned gaping or conditioned taste avoidance in rats. In rats and mice, AM6545 dose-dependently reduced food intake and induced a sustained reduction in body weight. The effect on food intake was maintained in rats with a complete subdiaphragmatic vagotomy. AM6545 inhibited food intake in CB(1) receptor gene-deficient mice, but not in CB(1)/CB(2) receptor double knockout mice.Conclusions and Implications: Peripherally active, cannabinoid receptor antagonists with limited brain penetration may be useful agents for the treatment of obesity and its complications. [ABSTRACT FROM AUTHOR]

Background and Purpose: Excessive production of nitric oxide (NO) by inducible NO synthase (iNOS) is thought to underlie the vascular dysfunction, systemic hypotension and organ failure that characterize endotoxic shock. Plasma levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) are raised in animal models and humans with endotoxic shock and correlate with the associated cardiovascular dysfunction. Since both NO and natriuretic peptides play important roles in cardiovascular homeostasis via activation of guanylate cyclase-linked receptors, we used mice lacking natriuretic peptide receptor (NPR)-A (NPR1) to establish if natriuretic peptides contribute to the cardiovascular dysfunction present in endotoxic shock.Experimental Approach: Wild-type (WT) and NPR-A knockout (KO) mice were exposed to lipopolysaccharide (LPS) and vascular dysfunction (in vitro and in vivo), production of pro-inflammatory cytokines, and iNOS expression and activity were evaluated.Key Results: LPS-treated WT animals exhibited a marked fall in mean arterial blood pressure (MABP) whereas NPR-A KO mice maintained MABP throughout. LPS administration caused a greater suppression of vascular responses to the thromboxane-mimetic U46619, ANP, acetylcholine and the NO-donor spermine-NONOate in WT versus NPR-A KO mice. This differential effect on vascular function was paralleled by reduced pro-inflammatory cytokine production, iNOS expression and activity (plasma [NO(x)] and cyclic GMP).Conclusions and Implications: These observations suggest that NPR-A activation by natriuretic peptides facilitates iNOS expression and contributes to the vascular dysfunction characteristic of endotoxic shock. Pharmacological interventions that target the natriuretic peptide system may represent a novel approach to treat this life-threatening condition. [ABSTRACT FROM AUTHOR]

Background and Purpose: F15599, a novel 5-hydroxytryptamine (5-HT)(1A) receptor agonist with 1000-fold selectivity for 5-HT compared with other monoamine receptors, shows antidepressant and procognitive activity at very low doses in animal models. We examined the in vivo activity of F15599 at somatodendritic autoreceptors and postsynaptic 5-HT(1A) heteroreceptors.Experimental Approach: In vivo single unit and local field potential recordings and microdialysis in the rat.Key Results: F15599 increased the discharge rate of pyramidal neurones in medial prefrontal cortex (mPFC) from 0.2 microg x kg(-1) i.v and reduced that of dorsal raphe 5-hydroxytryptaminergic neurones at doses >10-fold higher (minimal effective dose 8.2 microg x kg(-1) i.v.). Both effects were reversed by the 5-HT(1A) antagonist (+/-)WAY100635. F15599 did not alter low frequency oscillations (approximately 1 Hz) in mPFC. In microdialysis studies, F15599 increased dopamine output in mPFC (an effect dependent on the activation of postsynaptic 5-HT(1A) receptors) with an ED(50) of 30 microg x kg(-1) i.p., whereas it reduced hippocampal 5-HT release (an effect dependent exclusively on 5-HT(1A) autoreceptor activation) with an ED(50) of 240 microg x kg(-1) i.p. Likewise, application of F15599 by reverse dialysis in mPFC increased dopamine output in a concentration-dependent manner. All neurochemical responses to F15599 were prevented by administration of (+/-)WAY100635.Conclusions and Implications: These results indicate that systemic administration of F15599 preferentially activates postsynaptic 5-HT(1A) receptors in PFC rather than somatodendritic 5-HT(1A) autoreceptors. This regional selectivity distinguishes F15599 from previously developed 5-HT(1A) receptor agonists, which preferentially activate somatodendritic 5-HT(1A) autoreceptors, suggesting that F15599 may be particularly useful in the treatment of depression and of cognitive deficits in schizophrenia. [ABSTRACT FROM AUTHOR]

Background and Purpose: Increased glutamatergic innervation of the substantia nigra pars reticulata (SNpr) and pars compacta (SNpc) may contribute to the motor deficits and neurodegeneration, respectively, in Parkinson's disease (PD). This study aimed to establish whether activation of pre-synaptic group III metabotropic glutamate (mGlu) receptors reduced glutamate release in the SN, and provided symptomatic or neuroprotective relief in animal models of PD.Experimental Approach: Broad-spectrum group III mGlu receptor agonists, O-phospho-l-serine (l-SOP) and l-2-amino-4-phosphonobutyrate (l-AP4), were assessed for their ability to inhibit KCl-evoked [(3)H]-d-aspartate release in rat nigral prisms or inhibit KCl-evoked endogenous glutamate release in the SNpr in vivo using microdialysis. Reversal of akinesia in reserpine-treated rats was assessed following intranigral injection of l-SOP and l-AP4. Finally, the neuroprotective effect of 7 days' supra-nigral treatment with l-AP4 was examined in 6-hydroxydopamine (6-OHDA)-lesioned rats.Key Results: l-SOP and l-AP4 inhibited [(3)H]-d-aspartate release by 33 and 44% respectively. These effects were blocked by the selective group III mGlu antagonist (RS)-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG). l-SOP also reduced glutamate release in the SNpr in vivo by 48%. Injection of l-SOP and l-AP4 into the SNpr reversed reserpine-induced akinesia. Following administration above the SNpc, l-AP4 provided neurochemical, histological and functional protection against 6-OHDA lesion of the nigrostriatal tract. Pretreatment with CPPG inhibited these effects.Conclusions and Implications: These findings highlight group III mGlu receptors in the SN as potential targets for providing both symptomatic and neuroprotective relief in PD, and indicate that inhibition of glutamate release in the SN may underlie these effects. [ABSTRACT FROM AUTHOR]

Background and Purpose: The present study evaluated the role of CB(2) receptors in the regulation of depressive-like behaviours. Transgenic mice overexpressing the CB(2) receptor (CB2xP) were challenged with different types of acute and chronic experimental paradigms to evaluate their response in terms of depressive-like behaviours.Experimental Approach: Tail suspension test (TST), novelty-suppressed feeding test (NSFT) and unpredictable chronic mild stress tests (CMS) were carried out in CB2xP mice. Furthermore, acute and chronic antidepressant-like effects of the CB(2) receptor-antagonist AM630 were evaluated by means of the forced swimming test (FST) and CMS, respectively, in wild-type (WT) and CB2xP mice. CB(2) gene expression, brain-derived neurotrophic factor (BDNF) gene and protein expressions were studied in mice exposed to CMS by real-time PCR and immunohistochemistry, respectively.Key Results: Overexpression of CB(2) receptors resulted in decreased depressive-like behaviours in the TST and NSFT. CMS failed to alter the TST and sucrose consumption in CB2xP mice. In addition, no changes in BDNF gene and protein expression were observed in stressed CB2xP mice. Interestingly, acute administration of AM630 (1 and 3 mg x kg(-1), i.p.) exerted antidepressant-like effects on the FST in WT, but not in CB2xP mice. Chronic administration of AM630 for 4 weeks (1 mg x kg(-1); twice daily, i.p.) blocked the effects of CMS on TST, sucrose intake, CB(2) receptor gene, BDNF gene and protein expression in WT mice.Conclusion and Implications: Taken together, these results suggest that increased CB(2) receptor expression significantly reduced depressive-related behaviours and that the CB(2) receptor could be a new potential therapeutic target for depressive-related disorders. [ABSTRACT FROM AUTHOR]

Background and Purpose: Previous work has shown that N(G)-monomethyl-l-arginine (l-NMMA) paradoxically inhibits basal, but not ACh-stimulated activity of nitric oxide in rat aorta. The aim of this study was to determine if the endogenously produced agent, asymmetric N(G), N(G)-dimethyl-l-arginine (ADMA), also exhibits this unusual selective blocking action.Experimental Approach: The effect of ADMA on basal nitric oxide activity was assessed by examining its ability to enhance phenylephrine (PE)-induced tone in endothelium-containing rings. Its effect on ACh-induced relaxation was assessed both in conditions where ADMA greatly enhanced PE tone and where tone was carefully matched with control tissues at a range of different levels.Key Results: ADMA (100 microM) potentiated PE-induced contraction, consistent with inhibition of basal nitric oxide activity. Higher concentrations (300-1000 microM) had no greater effect. Although ADMA (100 microM) also appeared to block ACh-induced relaxation when it enhanced PE tone to maximal levels, virtually no block was seen at intermediate levels of tone in the presence of ADMA. Even ADMA at 1000 microM had no effect on the maximal relaxation to ACh, although it produced a small (two- to threefold) reduction in sensitivity. ADMA and l-NMMA, like l-arginine (all at 1000 microM), protected ACh-induced relaxation against blockade by l-NAME (30 microM).Conclusions and Implications: In the rat aorta, ADMA, like l-NMMA, blocks basal activity of nitric oxide, but has little effect on that stimulated by ACh. Further studies are required to explain these seemingly anomalous actions of ADMA and l-NMMA. [ABSTRACT FROM AUTHOR]

Background and Purpose: Oenanthotoxin (OETX), a polyacetylenic alcohol from plants of the genus Oenanthe, has recently been identified as potent inhibitor of GABA-evoked currents. However, the effects of OETX on the inhibitory postsynaptic currents (IPSCs), as well as the pharmacological mechanism(s) underlying its effects on GABA(A) receptors, remain unknown. The purpose of this study was to elucidate the mechanism underlying the inhibition of GABAergic currents by OETX.Experimental Approach: Effects of OETX on GABAergic currents were studied using the patch clamp technique on rat cultured hippocampal neurons. Miniature IPSCs (mIPSCs) were recorded in the whole-cell configuration, while the current responses were elicited by ultrafast GABA applications onto the excised patches.Key Results: OETX potently inhibited both mIPSCs and current responses, but its effect was much stronger on synaptic currents. Analysis of the effects of OETX on mIPSCs and evoked currents disclosed a complex mechanism: allosteric modulation of both GABA(A) receptor binding and gating properties and a non-competitive, probably open channel block mechanism. In particular, OETX reduced the binding rate and nearly abolished receptor desensitization. A combination of rapid clearance of synaptic GABA and OETX-induced slowing of binding kinetics is proposed to underlie the potent action of OETX on mIPSCs.Conclusions and Implications: OETX shows a complex blocking mechanism of GABA(A) receptors, and the impact of this toxin is more potent on mIPSCs than on currents evoked by exogenous GABA. Such effects on GABAergic currents are compatible with the convulsions and epileptic-like activity reported for OETX. [ABSTRACT FROM AUTHOR]

Background and Purpose: The sarcoplasmic reticulum (SR) releases Ca(2+) via inositol 1,4,5-trisphosphate receptors (IP(3)R) in response to IP(3)-generating agonists. Ca(2+) release subsequently propagates as Ca(2+) waves. To clarify the role of IP(3) production in wave generation, the contribution of a key enzyme in the production of IP(3) was examined using a phosphoinositide-specific phospholipase C (PI-PLC) inhibitor, U-73122.Experimental Approach: Single colonic myocytes were voltage-clamped in whole-cell configuration and cytosolic Ca(2+) concentration ([Ca(2+)](cyto)) measured using fluo-3. SR Ca(2+) release was evoked either by activation of IP(3)Rs (by carbachol or photolysis of caged IP(3)) or ryanodine receptors (RyRs; by caffeine).Key Results: U-73122 inhibited carbachol-evoked [Ca(2+)](cyto) transients. The drug also inhibited [Ca(2+)](cyto) increases, evoked by direct IP(3)R activation (by photolysis of caged IP(3)) and RyR activation (by caffeine), which do not require PI-PLC activation. U-73122 also increased steady-state [Ca(2+)](cyto) and slowed the rate of Ca(2+) removal from the cytoplasm. An inactive analogue of U-73122, U-73343, was without effect on either IP(3)R- or RyR-mediated Ca(2+) release.Conclusions and Implications: U-73122 inhibited carbachol-evoked [Ca(2+)](cyto) increases. However, the drug also reduced Ca(2+) release when evoked by direct activation of IP(3)R or RyR, slowed Ca(2+) removal and increased steady-state [Ca(2+)](cyto). These results suggest U-73122 reduces IP(3)-evoked Ca(2+) transients by inhibiting the SR Ca(2+) pump to deplete the SR of Ca(2+) rather than by inhibiting PI-PLC. [ABSTRACT FROM AUTHOR]

Background and Purpose: Current therapies for muscular dystrophy are based on corticosteroids. Significant side effects associated with these therapies have prompted several studies aimed at identifying possible alternative strategies. As inflammation and defects of nitric oxide (NO) generation are key pathogenic events in muscular dystrophies, we have studied the effects of combining the NO donor isosorbide dinitrate (ISDN) and the non-steroidal anti-inflammatory drug ibuprofen.Experimental Approach: alpha-Sarcoglycan-null mice were treated for up to 8 months with ISDN (30 mg.kg(-1)) plus ibuprofen (50 mg.kg(-1)) administered daily in the diet. Effects of ISDN and ibuprofen alone were assessed in parallel. Drug effects on animal motility and muscle function, muscle damage, inflammatory infiltrates and cytokine levels, as well as muscle regeneration including assessment of endogenous stem cell pool, were measured at selected time points.Key Results: Combination of ibuprofen and ISDN stimulated regeneration capacity, of myogenic precursor cells, reduced muscle necrotic damage and inflammation. Muscle function in terms of free voluntary movement and resistance to exercise was maintained throughout the time window analysed. The effects of ISDN and ibuprofen administered separately were transient and significantly lower than those induced by their combination.Conclusions and Implications: Co-administration of NO and ibuprofen provided synergistic beneficial effects in a mouse model of muscular dystrophy, leading to an effective therapy. Our results open the possibility of immediate clinical testing of a combination of ISDN and ibuprofen in dystrophic patients, as both components are approved for use in humans, with a good safety profile. [ABSTRACT FROM AUTHOR]

Background and Purpose: SKF96365 (SKF), originally identified as a blocker of receptor-mediated calcium entry, is widely used diagnostically, as a blocker of transient receptor potential canonical type (TRPC) channels. While SKF has been used as a tool to define the functional roles of TRPC channels in various cell and tissue types, there are notable overlapping physiological and pathophysiological associations between TRPC channels and low-voltage-activated (LVA) T-type calcium channels. The activity of SKF against T-type Ca channels has not been previously explored, and here we systematically investigated the effects of SKF on recombinant and native voltage-gated Ca channel-mediated currents.Experimental Approach: Effects of SKF on recombinant Ca channels were studied under whole-cell patch clamp conditions after expression in HEK293 cells. The effect of SKF on cerebellar Purkinje cells (PCs) expressing native T-type Ca channels was also assessed.Key Results: SKF blocked recombinant Ca channels, representative of each of the three main molecular genetic classes (Ca(V)1, Ca(V)2 and Ca(V)3) at concentrations typically utilized to assay TRPC function (10 microM). Particularly, human Ca(V)3.1 T-type Ca channels were more potently inhibited by SKF (IC(50) approximately 560 nM) in our experiments than previously reported for similarly expressed TRPC channels. SKF also inhibited native Ca(V)3.1 T-type currents in a rat cerebellar PC slice preparation.Conclusions and Implications: SKF was a potent blocker of LVA T-type Ca channels. We suggest caution in the interpretation of results using SKF alone as a diagnostic agent for TRPC activity in native tissues. [ABSTRACT FROM AUTHOR]

Background and Purpose: AE9C90CB (N- [(1R, 5S, 6R)-3-azabicyclo [3.1.0] hex-6-ylmethyl]-2-hydroxy-N-methyl-2, 2-diphenylacetamide), a novel muscarinic receptor antagonist, was synthesized for the treatment of overactive bladder. Here we describe the in vitro and in vivo profiles of AE9C90CB for action in bladder over salivary gland and compare it with four agents already in clinical use (tolterodine, oxybutynin, solifenacin and darifenacin).Experimental Approach: Radioligand binding assay and isolated tissue-based functional assay were used to evaluate affinity, potency, and receptor subtype selectivity of compounds. Inhibition of carbachol-induced increase in intravesicular pressure and salivary secretion were measured in anaesthetized rabbits to assess the functional selectivity.Key Results: In vitro radioligand binding study using human recombinant muscarinic receptors showed that AE9C90CB had greater affinity for M(3) muscarinic receptors with pKi of 9.90 +/- 0.11 and was 20-fold more selective for M(3) than for M(2) muscarinic receptors. AE9C90CB exhibited an unsurmountable antagonism on rat bladder strips (pK(B), 9.13 +/- 0.12). In anaesthetized rabbits after intravenous administration, AE9C90CB dose dependently inhibited carbachol-induced increase in intravesicular pressure and salivary secretion, and exhibited functional selectivity for urinary bladder over salivary gland which was ninefold better than that of oxybutynin.Conclusions and Implications: We have identified AE9C90CB, a compound exhibiting moderate selectivity for M(3) over M(2) receptors but greater selectivity for urinary bladder over salivary gland than oxybutynin, tolterodine, solifenacin and darifenacin. Therefore, AE9C90CB may be a promising compound for the treatment of overactive bladder with reduced potential to cause dry mouth than currently available antimuscarinic drugs. [ABSTRACT FROM AUTHOR]

Background and Purpose: Arteries from hypertensive subjects are reportedly hyperresponsive to 5-hydroxytryptamine (5-HT), but it remains unclear whether this is true in chronic type 2 diabetes. We have assessed responses to 5-HT shown by mesenteric arteries from type 2 diabetic ob/ob mice (27-32 weeks old) and have identified the molecular mechanisms involved.Experimental Approach: Contractions of mesenteric rings to 5-HT were examined in vitro. Activation of mesenteric RhoA, Rho kinase and Src was measured by Western blotting or by modified enzyme-linked immunosorbent assay.Key Results: Concentration-dependent contractions to 5-HT were greater in mesenteric rings from the ob/ob than in those from the age-matched control ('Lean') group. In each group, there was no significant change in the 5-HT-induced contractions after inhibition of nitric oxide synthase (with N(G)-nitro-L-arginine), of cyclooxygenase (with indomethacin) or of protein kinase C (with chelerythrine). However inhibition of the MEK/ERK pathway (with PD98059) decreased the response to 5-HT. Although the diabetes-related enhancement of the 5-HT response was preserved with each of these inhibitors, enhancement was abolished by a Rho kinase inhibitor (Y27632) and by Src kinase inhibitors (PP1 analogue or Src kinase inhibitor I). 5-HT-induced activation of RhoA, Rho kinase and Src kinase in mesenteric arteries was greater in the ob/ob than in the Lean group, but the expression of RhoA, Rho kinase isoforms and Src did not differ between these groups.Conclusions and Implications: These results suggest that the enhancement of 5-HT-induced contraction in mesenteric arteries from ob/ob mice may be attributable to increased activation of RhoA/Rho kinase and Src kinase. [ABSTRACT FROM AUTHOR]

Background and Purpose: Lopinavir is extensively metabolized by cytochrome P450 3A (CYP3A) and is considered to be a substrate for the drug transporters ABCB1 (P-glycoprotein) and ABCC2 (MRP2). Here, we have assessed the individual and combined effects of CYP3A, ABCB1 and ABCC2 on the pharmacokinetics of lopinavir and the relative importance of intestinal and hepatic metabolism. We also evaluated whether ritonavir increases lopinavir oral bioavailability by inhibition of CYP3A, ABCB1 and/or ABCC2.Experimental Approach: Lopinavir transport was measured in Madin-Darby canine kidney cells expressing ABCB1 or ABCC2. Oral lopinavir kinetics (+/- ritonavir) was studied in mice with genetic deletions of Cyp3a, Abcb1a/b and/or Abcc2, or in transgenic mice expressing human CYP3A4 exclusively in the liver and/or intestine.Key Results: Lopinavir was transported by ABCB1 but not by ABCC2 in vitro. Lopinavir area under the plasma concentration - time curve (AUC)(oral) was increased in Abcb1a/b(-/-) mice (approximately ninefold vs. wild-type) but not in Abcc2(-/-) mice. Increased lopinavir AUC(oral) (>2000-fold) was observed in cytochrome P450 3A knockout (Cyp3a(-/-)) mice compared with wild-type mice. No difference in AUC(oral) between Cyp3a(-/-) and Cyp3a/Abcb1a/b/Abcc2(-/-) mice was observed. CYP3A4 activity in intestine or liver, separately, reduced lopinavir AUC(oral) (>100-fold), compared with Cyp3a(-/-) mice. Ritonavir markedly increased lopinavir AUC(oral) in all CYP3A-containing mouse strains.Conclusions and Implications: CYP3A was the major determinant of lopinavir pharmacokinetics, far more than Abcb1a/b. Both intestinal and hepatic CYP3A activity contributed importantly to low oral bioavailability of lopinavir. Ritonavir increased lopinavir bioavailability primarily by inhibiting CYP3A. Effects of Abcb1a/b were only detectable in the presence of CYP3A, suggesting saturation of Abcb1a/b in the absence of CYP3A activity. [ABSTRACT FROM AUTHOR]

Background and Purpose: Caffeine exacerbates the hyperthermia associated with an acute exposure to 3,4 methylenedioxymethamphetamine (MDMA, 'Ecstasy') in rats. The present study investigated the mechanisms mediating this interaction.Experimental Approach: Adult male Sprague-Dawley rats were treated with caffeine (10 mg x kg(-1); i.p.) and MDMA (15 mg x kg(-1); i.p.) alone and in combination. Core body temperatures were monitored before and after drug administration.Key Results: Central catecholamine depletion blocked MDMA-induced hyperthermia and its exacerbation by caffeine. Caffeine provoked a hyperthermic response when the catecholamine releaser d-amphetamine (1 mg x kg(-1)) was combined with the 5-HT releaser D-fenfluramine (5 mg x kg(-1)) or the non-selective dopamine receptor agonist apomorphine (1 mg x kg(-1)) was combined with the 5-HT(2) receptor agonist DOI (2 mg x kg(-1)) but not following either agents alone. Pretreatment with the dopamine D(1) receptor antagonist Schering (SCH) 23390 (1 mg x kg(-1)), the 5-HT(2) receptor antagonist ketanserin (5 mg x kg(-1)) or alpha(1)-adreno- receptor antagonist prazosin (0.2 mg x kg(-1)) blocked MDMA-induced hyperthermia and its exacerbation by caffeine. Co-administration of a combination of MDMA with the PDE-4 inhibitor rolipram (0.025 mg x kg(-1)) and the adenosine A(1/2) receptor antagonist 9-chloro-2-(2-furanyl)-[1,2,4]triazolo[1,5-C]quinazolin-5-amine 15943 (10 mg x kg(-1)) or the A(2A) receptor antagonist SCH 58261 (2 mg x kg(-1)) but not the A(1) receptor antagonist DPCPX (10 mg x kg(-1)) exacerbated MDMA-induced hyperthermia.Conclusions and Implications: A mechanism comprising 5-HT and catecholamines is proposed to mediate MDMA-induced hyperthermia. A combination of adenosine A(2A) receptor antagonism and PDE inhibition can account for the exacerbation of MDMA-induced hyperthermia by caffeine. [ABSTRACT FROM AUTHOR]

Background and Purpose: KMUP-1 is known to increase cGMP, enhance endothelial nitric oxide synthase (eNOS) and suppress Rho kinase (ROCK) expression in smooth muscle. Here, we investigated the mechanism of action of KMUP-1 on acute and chronic pulmonary artery hypertension (PAH) in rats.Experimental Approach: We measured pulmonary vascular contractility, wall thickening, eNOS immunostaining, expressions of ROCK II, RhoA activation, myosin phosphatase target subunit 1 (MYPT1) phosphorylation, eNOS, soluble guanylyl cyclase (sGC), protein kinase G (PKG) and phosphodiesterase 5A (PDE-5A), blood oxygenation and cGMP/cAMP, and right ventricular hypertrophy (RVH) in rats.Key Results: In rings of intact pulmonary artery (PA), KMUP-1 relaxed the vasoconstriction induced by phenylephrine (10 microM) or the thromboxane A(2)-mimetic U46619 (0.5 microM). In endothelium-denuded PA rings, this relaxation was reduced. In acute PAH induced by U46619 (2.5 microg x kg(-1) x min(-1), 30 min), KMUP-1 relaxed vasoconstriction by enhancing levels of eNOS, sGC and PKG, suppressing those of PDE-5A, RhoA/ROCK II activation and MYPT1 phosphorylation, and restoring oxygenation in blood and cGMP/cAMP in plasma. Incubating smooth muscle cells from PA (PASMCs) with KMUP-1 inhibited thapsigargin-induced Ca(2+) efflux and angiotensin II-induced Ca(2+) influx. In chronic PAH model induced by monocrotaline, KMUP-1 increased eNOS and reduced RhoA/ROCK II activation/expression, PA wall thickening, eNOS immunostaining and RVH. KMUP-1 and sildenafil did not inhibit monocrotaline-induced PDE-5A expression.Conclusion and Implications: KMUP-1 decreased PAH by enhancing NO synthesis by eNOS, with consequent cGMP-dependent inhibition of RhoA/ROCK II and Ca(2+) desensitization in PASMCs. KMUP-1 has the potential to reduce vascular resistance, remodelling and RVH in PAH. [ABSTRACT FROM AUTHOR]

Background and Purpose: Recent studies suggest that the effects of cyclooxygenase-2 (COX-2) inhibition are mediated by cannabinoid receptor activation. However, some non-steroidal anti-inflammatory drugs inhibit the enzyme fatty acid amide hydrolase, which regulates levels of some endocannabinoids. Whether COX-2 directly regulates levels of endocannabinoids in vivo is unclear. Here, the effect of the COX-2 inhibitor nimesulide, which does not inhibit fatty acid amide hydrolase, on spinal nociceptive processing was determined. Effects of nimesulide on tissue levels of endocannabinoids and related compounds were measured and the role of cannabinoid 1 (CB(1)) receptors was determined.Experimental Approach: Effects of spinal and peripheral administration of nimesulide (1-100 microg per 50 microL) on mechanically evoked responses of rat dorsal horn neurones were measured, and the contribution of the CB(1) receptor was determined with the antagonist AM251 (N-(piperidin-1-yl)-5-(-4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide), in anaesthetized rats. Effects of nimesulide on spinal levels of endocannabinoids and related compounds were quantified using liquid chromatography-tandem mass spectrometry.Key Results: Spinal, but not peripheral, injection of nimesulide (1-100 microg per 50 microL) significantly reduced mechanically evoked responses of dorsal horn neurones. Inhibitory effects of spinal nimesulide were blocked by the CB(1) receptor antagonist AM251 (1 microg per 50 microL), but spinal levels of endocannabinoids were not elevated. Indeed, both anandamide and N-oleoylethanolamide (OEA) were significantly decreased by nimesulide.Conclusions and Implications: Although the inhibitory effects of COX-2 blockade on spinal neuronal responses by nimesulide were dependent on CB(1) receptors, we did not detect a concomitant elevation in anandamide or 2-AG. Further understanding of the complexities of endocannabinoid catabolism by multiple enzymes is essential to understand their contribution to COX-2-mediated analgesia. [ABSTRACT FROM AUTHOR]

Background and Purpose: The endocannabinoid-like molecule N-oleoylethanolamine (OEA) is found in the small intestine and regulates food intake and promotes weight loss. The principal aim of the present study was to evaluate the vascular effects of OEA.Experimental Approach: Perfused isolated mesenteric arterial beds were pre-contracted with methoxamine or high potassium buffers and concentration-response curves to OEA were constructed. Combinations of inhibitors to block nitric oxide production, sensory nerve activity, cyclooxygenase activity, potassium channels, chloride channels and gap junctions, and a cannabinoid CB(1) receptor antagonist, were used during these experiments. The effects of OEA on caffeine-induced contractions in calcium-free buffer were also assessed. Isolated thoracic aortic rings were used as a comparison.Key Results: OEA caused concentration-dependent vasorelaxation in rat isolated mesenteric arterial beds and thoracic aortic rings, with a greater maximal response in mesenteric vessels. This relaxation was sensitive to inhibition of sensory nerve activity and endothelial removal in both preparations. The cyclooxygenase inhibitor indomethacin reversed the effects of capsaicin pre-treatment in perfused mesenteric arterial beds and indomethacin alone enhanced vasorelaxation to OEA. The OEA-induced vasorelaxation was inhibited by a CB(1) receptor antagonist only in aortic rings. In mesenteric arteries, OEA suppressed caffeine-induced contractions in calcium-free buffer.Conclusions and Implications: The vasorelaxant effects of OEA are partly dependent on sensory nerve activity and a functional endothelium in the vasculature. In addition, vasorelaxation to OEA is enhanced following cyclooxygenase inhibition. OEA may also interfere with the release of intracellular calcium in arterial preparations. [ABSTRACT FROM AUTHOR]

Background and Purpose: In various models vagus nerve activation has been shown to ameliorate intestinal inflammation, via nicotinic acetylcholine receptors (nAChRs) expressed on immune cells. As the alpha7 nAChR has been put forward to mediate this effect, we studied the effect of nicotine and two selective alpha7 nAChR agonists (AR-R17779, (-)-spiro[1-azabicyclo[2.2.2] octane-3,5'-oxazolidin-2'-one and GSK1345038A) on disease severity in two mouse models of experimental colitis.Experimental Approach: Colitis was induced by administration of 1.5% dextran sodium sulphate (DSS) in drinking water or 2 mg 2,4,6-trinitrobenzene sulphonic acid (TNBS) intrarectally. Nicotine (0.25 and 2.50 micromol.kg(-1)), AR-R17779 (0.6-30 micromol.kg(-1)) or GSK1345038A (6-120 micromol.kg(-1)) was administered daily by i.p. injection. After 7 (DSS) or 5 (TNBS) days clinical parameters and colonic inflammation were scored.Key Results: Nicotine and both alpha7 nAChR agonists reduced the activation of NF-kappaB and pro-inflammatory cytokines in whole blood and macrophage cultures. In DSS colitis, nicotine treatment reduced colonic cytokine production, but failed to reduce disease parameters. Reciprocally, treatment with AR-R17779 or GSK1345038A worsened disease and led to increased colonic pro-inflammatory cytokine levels in DSS colitis. The highest doses of GSK1345038A (120 micromol.kg(-1)) and AR-R17779 (30 micromol.kg(-1)) ameliorated clinical parameters, without affecting colonic inflammation. Neither agonist ameliorated TNBS-induced colitis.Conclusions and Implications: Although nicotine reduced cytokine responses in vitro, both selective alpha7 nAChR agonists worsened the effects of DSS-induced colitis or were ineffective in those of TNBS-induced colitis. Our data indicate the need for caution in evaluating alpha7 nAChR as a drug target in colitis. [ABSTRACT FROM AUTHOR]

Background and Purpose: Some neurosteroids, notably 3alpha-hydroxysteroids, positively modulate GABA(A) receptors, but sulphated steroids negatively modulate these receptors. Recently, other lipophilic amphiphiles have been suggested to positively modulate GABA receptors. We examined whether there was similarity among the actions of these agents and the mechanisms of neurosteroids. Significant similarity would affect theories about the specificity of steroid actions.Experimental Approach: Xenopus laevis oocytes were challenged with Triton X-100, octyl-beta-glucoside, capsaicin, docosahexaenoic acid and sodium dodecyl sulphate (SDS), along with different GABA concentrations.Key Results: These compounds have both positive and negative effects on GABA currents, which can be accentuated according to the degree of receptor activation. A low GABA concentration (1 microM) promoted potentiation and a high concentration (20 microM) promoted inhibition of current, except for SDS that inhibited function even at low GABA concentrations. Amphiphile inhibition was characterized by enhanced apparent desensitization and by weak voltage dependence, similar to pregnenolone sulphate antagonism. We then tested amphiphile effects on mutated receptor subunits that are insensitive to negative (alpha1V256S) and positive (alpha1Q241L or alpha1N407A/Y410F) steroid modulation. Negative regulation by amphiphiles was nearly abolished in alpha1V256S-mutated receptors, but potentiation was unaffected. In alpha1Q241L- or alpha1N407A/Y410F-mutated receptors, potentiation by amphiphiles remained intact.Conclusions and Implications: Structurally diverse amphiphiles have antagonist actions at GABA(A) receptors very similar to those of sulphated neurosteroids, while the potentiating mechanisms of these amphiphiles are distinct from those of neurosteroid-positive modulators. Thus, such antagonism at GABA(A) receptors does not have a clear pharmacophore requirement. [ABSTRACT FROM AUTHOR]

Background and Purpose: Genetic approaches have documented protein kinase B (PKB) as a pivotal regulator of heart function. Insulin strongly activates PKB, whereas adrenaline is not considered a major physiological regulator of PKB in heart. In skeletal muscles, however, adrenaline potentiates insulin-stimulated PKB activation without having effect in the absence of insulin. The purpose of the present study was to investigate the interaction between insulin and beta-adrenergic stimulation in regulation of PKB phosphorylation.Experimental Approach: Cardiomyocytes were isolated from adult rats by collagenase, and incubated with insulin, isoprenaline, and other compounds. Protein phosphorylation was evaluated by Western blot and phospho-specific antibodies.Key Results: Isoprenaline increased insulin-stimulated PKB Ser(473) and Thr(308) phosphorylation more than threefold in cardiomyocytes. Isoprenaline alone did not increase PKB phosphorylation. Isoprenaline also increased insulin-stimulated GSK-3beta Ser(9) phosphorylation approximately twofold, supporting that PKB phosphorylation increased kinase activity. Dobutamine (beta(1)-agonist) increased insulin-stimulated PKB phosphorylation as effectively as isoprenaline (more than threefold), whereas salbutamol (beta(2)-agonist) only potentiated insulin-stimulated PKB phosphorylation by approximately 80%. Dobutamine, but not salbutamol, increased phospholamban Ser(16) phosphorylation and glycogen phosphorylase activation (PKA-mediated effects). Furthermore, the cAMP analogue that activates PKA (dibutyryl-cAMP and N(6)-benzoyl-cAMP) increased insulin-stimulated PKB phosphorylation by more than threefold without effect alone. The Epac-specific activator 8-(4-chlorophenylthio)-2'-O-methyl-cAMP (007) increased insulin-stimulated PKB phosphorylation by approximately 50%. Db-cAMP and N(6)-benzoyl-cAMP, but not 007, increased phospholamban Ser(16) phosphorylation.Conclusions and Implications: beta-adrenoceptors are strong regulators of PKB phosphorylation via cAMP and PKA when insulin is present. We hypothesize that PKB mediates important signalling in the heart during beta-adrenergic receptors stimulation. [ABSTRACT FROM AUTHOR]

Background and Purpose: Over three decades of research evaluating the biology of melanocortin (MC) hormones and synthetic peptides, activation of the MC type 1 (MC(1)) receptor has been identified as a viable target for the development of novel anti-inflammatory therapeutic agents. Here, we have tested a recently described selective agonist of MC(1) receptors, BMS-470539, on leucocyte/post-capillary venule interactions in murine microvascular beds.Experimental Approach: Intravital microscopy of two murine microcirculations were utilized, applying two distinct modes of promoting inflammation. The specificity of the effects of BMS-470539 was assessed using mice bearing mutant inactive MC(1) receptors (the recessive yellow e/e colony).Key Results: BMS-470539, given before an ischaemia-reperfusion protocol, inhibited cell adhesion and emigration with no effect on cell rolling, as assessed 90 min into the reperfusion phase. These properties were paralleled by inhibition of tissue expression of both CXCL1 and CCL2. Confocal investigations of inflamed post-capillary venules revealed immunostaining for MC(1) receptors on adherent and emigrated leucocytes. Congruently, the anti-inflammatory properties of BMS-470539 were lost in mesenteries of mice bearing the inactive mutant MC(1) receptors. Therapeutic administration of BMS-470539 stopped cell emigration, but did not affect cell adhesion in the cremasteric microcirculation inflamed by superfusion with platelet-activating factor.Conclusions and Implications: Activation of MC(1) receptors inhibited leucocyte adhesion and emigration. Development of new chemical entities directed at MC(1) receptors could be a viable approach in the development of novel anti-inflammatory therapeutic agents with potential application to post-ischaemic conditions. [ABSTRACT FROM AUTHOR]

Background and Purpose: Amitriptyline is a tricyclic antidepressant that is also widely used to treat neuropathic pain in humans, but the mechanism of this anti-hyperalgesic effect is unknown. Microglia in the mouse spinal cord become activated in neuropathic pain, and expression of P2X4 receptors by these microglia is increased. Antisense RNA targeting P2X4 receptors suppresses the development of tactile allodynia in rats. This suggests that blockade of P2X4 receptors might be the mechanism by which amitriptyline relieves neuropathic pain.Experimental Approach: We expressed human, rat and mouse P2X receptors (P2X2, P2X4, P2X7) in human embryonic kidney cells and evoked inward currents by applying ATP. We compared the action of ATP on control cells and cells treated with amitriptyline.Key Results: Amitriptyline (10 microM), either applied acutely or by pre-incubation for 2-6 h, had no effect on inward currents evoked by ATP (0.3-100 microM) at human P2X4 receptors. At rat and mouse receptors, amitriptyline (10 microM) caused a modest reduction in the maximum responses to ATP, without changes in EC(50) values, but it had no effect at 1 microM. Amitriptyline also had no effects on currents evoked by ATP at rat P2X2 receptors, or at rat or human P2X7 receptors.Conclusion and Implications: The results do not support the view that amitriptyline owes its pain-relieving actions in man to the direct blockade of P2X4 receptors. [ABSTRACT FROM AUTHOR]

Background and Purpose: Pentamidine is a drug used in treatment of protozoal infections. Pentamidine treatment may cause sudden cardiac death by provoking cardiac arrhythmias associated with QTc prolongation and U-wave alterations. This proarrhythmic effect was linked to inhibition of hERG trafficking, but not to acute block of ion channels contributing to the action potential. Because the U-wave has been linked to the cardiac inward rectifier current (I(K1)), we examined the action and mechanism of pentamidine-mediated I(K1) block.Experimental Approach: Patch clamp measurements of I(K1) were made on cultured adult canine ventricular cardiomyocytes, K(IR)2.1-HEK293 cells and K(IR)2.x inside-out patches. Pentamidine binding to cytoplasmic amino acid residues of K(IR)2.1 channels was studied by molecular modelling.Key Results: Pentamidine application (24 h) decreased I(K1) in cultured canine cardiomyocytes and K(IR)2.1-HEK293 cells under whole cell clamp conditions. Pentamidine inhibited I(K1) in K(IR)2.1-HEK293 cells 10 min after application. When applied to the cytoplasmic side under inside-out patch clamp conditions, pentamidine block of I(K1) was acute (IC(50)= 0.17 microM). Molecular modelling predicted pentamidine-channel interactions in the cytoplasmic pore region of K(IR)2.1 at amino acids E224, D259 and E299. Mutation of these conserved residues to alanine reduced pentamidine block of I(K1). Block was independent of the presence of spermine. K(IR)2.2, and K(IR)2.3 based I(K1) was also sensitive to pentamidine blockade.Conclusions and Implications: Pentamidine inhibits cardiac I(K1) by interacting with three negatively charged amino acids in the cytoplasmic pore region. Our findings may provide new insights for development of specific I(K1) blocking compounds. [ABSTRACT FROM AUTHOR]

Background and Purpose: Neuronal ion channels are key targets of general anaesthetics and alcohol, and binding of these drugs to pre-existing and relatively specific sites is thought to alter channel gating. However, the underlying molecular mechanisms of this action are still poorly understood. Here, we investigated the neuronal Shaw2 voltage-gated K(+) (K(v)) channel to ask whether the inhalational anaesthetic halothane and n-alcohols share a binding site near the activation gate of the channel.Experimental Approach: Focusing on activation gate mutations that affect channel modulation by n-alcohols, we investigated n-alcohol-sensitive and n-alcohol-resistant K(v) channels heterologously expressed in Xenopus oocytes to probe the functional modulation by externally applied halothane using two-electrode voltage clamping and a gas-tight perfusion system.Key Results: Shaw2 K(v) channels are reversibly inhibited by halothane in a dose-dependent and saturable manner (K(0.5)= 400 microM; n(H)= 1.2). Also, discrete mutations in the channel's S4S5 linker are sufficient to reduce or confer inhibition by halothane (Shaw2-T330L and K(v)3.4-G371I/T378A respectively). Furthermore, a point mutation in the S6 segment of Shaw2 (P410A) converted the halothane-induced inhibition into halothane-induced potentiation. Lastly, the inhibition resulting from the co-application of n-butanol and halothane is consistent with the presence of overlapping binding sites for these drugs and weak binding cooperativity.Conclusions and Implications: These observations strongly support a molecular model of a general anaesthetic binding site in the Shaw2 K(v) channel. This site may involve the amphiphilic interface between the S4S5 linker and the S6 segment, which plays a pivotal role in K(v) channel activation. [ABSTRACT FROM AUTHOR]

Background and Purpose: It is well known that adenine-based purines exert multiple effects on pain transmission. However, less attention has been given to the potential effects of guanine-based purines on pain transmission. The aim of this study was to investigate the effects of intraperitoneal (i.p.) and oral (p.o.) administration of guanosine on mice pain models. Additionally, investigation into the mechanisms of action of guanosine, its potential toxicity and cerebrospinal fluid (CSF) purine levels were also assessed.Experimental Approach: Mice received an i.p. or p.o. administration of vehicle (0.1 mM NaOH) or guanosine (up to 240 mg x kg(-1)) and were evaluated in several pain models.Key Results: Guanosine produced dose-dependent antinociceptive effects in the hot-plate, glutamate, capsaicin, formalin and acetic acid models, but it was ineffective in the tail-flick test. Additionally, guanosine produced a significant inhibition of biting behaviour induced by i.t. injection of glutamate, AMPA, kainate and trans-ACPD, but not against NMDA, substance P or capsaicin. The antinociceptive effects of guanosine were prevented by selective and non-selective adenosine receptor antagonists. Systemic administration of guanosine (120 mg x kg(-1)) induced an approximately sevenfold increase on CSF guanosine levels. Guanosine prevented the increase on spinal cord glutamate uptake induced by intraplantar capsaicin.Conclusions and Implications: This study provides new evidence on the mechanism of action of the antinociceptive effects after systemic administration of guanosine. These effects seem to be related to the modulation of adenosine A(1) and A(2A) receptors and non-NMDA glutamate receptors. [ABSTRACT FROM AUTHOR]

Background and Purpose: Much interest is currently being focused on the anti-nociceptive effects mediated by nicotinic acetylcholine (nACh) receptors, including their location and mechanism of action. The purpose of this study was to elucidate these issues using 5-iodo-3-(2(S)-azetidinylmethoxy)pyridine (5IA), a nACh receptor agonist, and [(125)I]5IA.Experimental Approach: We partially ligated the sciatic nerve of Sprague-Dawley rat to induce neuropathic pain [Seltzer's partial sciatic nerve ligation (PSL) model]. We then examined the changes in nACh receptor density in the CNS using [(125)I]5IA autoradiography and the involvement of nACh receptors in anti-nociceptive effects in the region where changes occurred.Key Results: Autoradiographic studies showed that the accumulation of [(125)I]5IA and the number of nACh receptors in the thalamus of PSL rats were increased about twofold compared with those in the sham-operated rats. No change was observed in other brain regions. Rats injected in the ventral posterolateral thalamic nucleus (VPL) with 5IA demonstrated a significant and dose-dependent anti-allodynic effect and this effect was completely antagonized by mecamylamine, injected with 5IA, into the VPL. The blockade of nACh receptors in the VPL by mecamylamine decreased by 70% the anti-allodynic effect of 5IA, given i.c.v. Moreover, mecamylamine given intra-VPL by itself, induced significant hyperalgesia.Conclusions and Implications: Our findings suggest that the nACh receptors expressed in the VPL play an important role in the anti-allodynic effects produced by exogenous and endogenous agonists. [ABSTRACT FROM AUTHOR]

Background and Purpose: To determine whether KMUP-1, a novel xanthine-based derivative, attenuates isoprenaline (ISO)-induced cardiac hypertrophy in rats, and if so, whether the anti-hypertrophic effect is mediated by the nitric oxide (NO) pathway.Experimental Approach: In vivo, cardiac hypertrophy was induced by injection of ISO (5 mg.kg(-1).day(-1), s.c.) for 10 days in Wistar rats. In the treatment group, KMUP-1 was administered 1 h before ISO. After 10 days, effects of KMUP-1 on survival, cardiac hypertrophy and fibrosis, the NO/guanosine 3'5'-cyclic monophosphate (cGMP)/protein kinase G (PKG) and hypertrophy signalling pathways [calcineurin A and extracellular signal-regulated kinase (ERK)1/2] were examined. To investigate the role of nitric oxide synthase (NOS) in the effects of KMUP-1, a NOS inhibitor, N(omega)-nitro-L-arginine (L-NNA) was co-administered with KMUP-1. In vitro, anti-hypertrophic effects of KMUP-1 were studied in ISO-induced hypertrophic neonatal rat cardiomyocytes.Key Results: In vivo, KMUP-1 pretreatment attenuated the cardiac hypertrophy and fibrosis and improved the survival of ISO-treated rats. Plasma NOx (nitrite and nitrate) and cardiac endothelial NOS, cGMP and PKG were all increased by KMUP-1. The activation of hypertrophic signalling by calcineurin A and ERK1/2 in ISO-treated rats was also attenuated by KMUP-1. All these effects of KMUP-1 were inhibited by simultaneous administration of L-NNA. Similarly, in vitro, KMUP-1 attenuated hypertrophic responses and signalling induced by ISO in neonatal rat cardiomyocytes.Conclusions and Implications: KMUP-1 attenuates the cardiac hypertrophy in rats induced by administration of ISO. These effects are mediated, at least in part, by NOS activation. This novel agent, which targets the NO/cGMP pathway, has a potential role in the prevention of cardiac hypertrophy. [ABSTRACT FROM AUTHOR]

Background and Purpose: In adults, neurogenesis persists in the hippocampus and the subventricular zone (SVZ), and this is important for learning and memory. Inhibitors of COX-2 suppress ischaemia-induced neurogenesis in the hippocampus. Here, we have determined the effects of COX-2 inhibitors on neurogenesis throughout the normal adult mouse brain.Experimental Approach: Young adult mice were treated with COX-2 inhibitors, and the proliferation of neural progenitor cells was measured in the SVZ and hippocampus. In addition, the local uptake of lentiviral vectors in the rostral migratory stream enabled the formation of new neurons in the olfactory bulb (OB) to be assessed.Key Results: The COX-2 inhibitor meloxicam suppressed progenitor cell proliferation in the SVZ and hippocampus. A significant decrease in the appearance of new neurons in the OB was also observed. Similar effects on progenitor proliferation in the SVZ were seen with nimesulide. The absence of COX-2 expression in the proliferating progenitors in vivo, and the lack of effect of the COX-2 inhibitors on the growth rate of a cultured progenitor cell line, suggest that the effect is indirect. The specific expression of COX-2 in resting microglia that closely associate with the proliferating progenitor cells provides for a possible site of action.Conclusions and Implications: Treatment with a COX-2 inhibitor results in a substantial inhibition of adult neurogenesis. Studies on human tissues are warranted in order to determine if this effect extends to humans, and whether inhibition of neurogenesis should be considered as an adverse effect of these drugs. [ABSTRACT FROM AUTHOR]

Background and Purpose: Hyperglycaemia is known to reduce nitric oxide (NO) bioavailability by modulating endothelial NO synthase (eNOS) activity, and polyphenols are believed to have cardiovascular benefit. One possible mechanism could be through interaction with eNOS.Experimental Approach: The effects of the oligomerized polyphenol oligonol on eNOS phosphorylation status and activity were examined in porcine aortic endothelial cells cultured in high glucose concentrations.Key Results: Exposure to high glucose concentrations strongly inhibited eNOS phosphorylation at Ser-1177 and dephosphorylation at Thr-495 in bradykinin (BK)-stimulated cells. These inhibitory effects of high glucose were significantly prevented by treatment with oligonol. Akt and p38 mitogen-activated protein kinase (MAPK) were activated in BK-stimulated cells. High glucose inhibited Akt activation but enhanced p38 MAPK activation, both of which were reversed by oligonol treatment. The phosphatidylinositol 3-kinase inhibitor wortmannin blocked the reversal by oligonol of phosphorylation at Ser-1177, but not dephosphorylation at Thr-495, in BK-stimulated cells exposed to high glucose. The effect of oligonol on BK dephosphorylation under high glucose was mimicked by protein kinase C (PKC) epsilon-neutralizing peptides. These data suggest that the effects of oligonol on high glucose-induced attenuation of eNOS Ser-1177 phosphorylation and Thr-495 dephosphorylation may be regulated by Akt activation and PKCepsilon inhibition respectively. Oligonol also prevented high glucose-induced attenuation of BK-stimulated NO production.Conclusions and Implications: Oligonol prevented the impairment of eNOS activity induced by high glucose through reversing altered eNOS phosphorylation status. This mechanism may underlie the beneficial cardiovascular health effects of this oligomerized polyphenol. [ABSTRACT FROM AUTHOR]

Background and Purpose: Big endothelin-1 (ET-1) circulates in plasma but does not bind to ET receptors until converted to ET-1 by smooth muscle converting enzymes. We hypothesized that tissue-specific conversion of [(18)F]-big ET-1 to [(18)F]-ET-1 could be imaged dynamically in vivo within target organs as binding to ET receptors.Methods: [(18)F]-big ET-1 conversion imaged in vivo following infusion into rats using positron emission tomography (PET).Key Results: [(18)F]-big ET-1 was rapidly cleared from the circulation (t(1/2)= 2.9 +/- 0.1 min). Whole body microPET images showed highest uptake of radioactivity in three major organs. In lungs and liver, time activity curves peaked within 2.5 min, then plateaued reaching equilibrium after 10 min, with no further decrease after 120 min. Phosphoramidon did not alter half life of [(18)F]-big ET-1 but uptake was reduced in lung (42%) and liver (45%) after 120 min, consistent with inhibition of enzyme conversion and reduction of ET-1 receptor binding. The ET(A) antagonist, FR139317 did not alter half-life of [(18)F]-big ET-1 (t(1/2)= 2.5 min) but radioactivity was reduced in all tissues except for kidney consistent with reduction in binding to ET(A) receptors. In kidney, however, the peak in radioactivity was higher but time to maximum accumulation was slower ( approximately 30 min), which was increased by phosphoramidon, reflecting renal excretion with low conversion and binding to ET receptors.Conclusions and Implications: A major site for conversion was within the vasculature of the lung and liver, whereas uptake in kidney was more complex, reflecting excretion of [(18)F]-big ET-1 without conversion to ET-1. [ABSTRACT FROM AUTHOR]

Background and Purpose: Tetrandrine, a well-known naturally occurring calcium antagonist with anti-inflammatory, antioxidant and anti-fibrogenetic activities, has long been used clinically for treatment of cardiovascular diseases such as hypertension and arrhythmia. However, little is known about the effect of tetrandrine on cardiac hypertrophy. The aims of the present study were to determine whether tetrandrine could attenuate cardiac hypertrophy and to clarify the underlying molecular mechanisms.Experimental Approach: Tetrandrine (50 mg x kg(-1) x day(-1)) was administered by oral gavage three times a day for one week and then the mice were subjected to either chronic pressure overload generated by aortic banding (AB) or sham surgery (control group). Cardiac function was determined by echocardiography.Key Results: Tetrandrine attenuated the cardiac hypertrophy induced by AB, as assessed by heart weight/body weight and lung weight/body weight ratios, cardiac dilatation and the expression of genes of hypertrophic markers. Tetrandrine also inhibited fibrosis and attenuated the inflammatory response. The cardioprotective effects of tetrandrine were mediated by blocking the increased production of reactive oxygen species and the activation of ERK1/2-dependent nuclear factor-kappaB and nuclear factor of activated T cells that occur in response to hypertrophic stimuli.Conclusions and Implications: Taken together, our results suggest that tetrandrine can improve cardiac function and prevent the development of cardiac hypertrophy by suppressing the reactive oxygen species-dependent ERK1/2 signalling pathway. [ABSTRACT FROM AUTHOR]

Background and Purpose: Current single drug treatments for rheumatoid arthritis have problems of limited efficacy and/or high toxicity. This study investigates the benefits of individual and combined treatments with dexamethasone and substance P and glutamate receptor antagonists in a rat model of arthritis.Experimental Approach: Arthritis was induced in rats by unilateral intra-articular injection of Freund's complete adjuvant. Separate groups of rats were subjected to the following treatments 15 min before induction of arthritis: (i) control with no drug treatment; (ii) single intra-articular injection of a NK(1) receptor antagonist RP67580; (iii) single intra-articular injection of a NMDA receptor antagonist AP7 plus a non-NMDA receptor antagonist CNQX; (iv) daily oral dexamethasone; and (v) combined treatment with dexamethasone and all of the above receptor antagonists. Knee joint allodynia, swelling, hyperaemia and histological changes were examined over a period of 7 days.Key Results: Treatment with dexamethasone suppressed joint swelling, hyperaemia and histological changes that include polymorphonuclear cell infiltration, synovial tissue proliferation and cartilage erosion in the arthritic rat knees. Treatment with RP67580 or AP7 plus CNQX did not attenuate hyperaemia or histological changes, but reduced joint allodynia and swelling. Co-administration of dexamethasone with these receptor antagonists produced greater inhibition on joint allodynia and swelling than their individual effects.Conclusions and Implications: The data suggest substance P and glutamate contribute to arthritic pain and joint swelling. The efficacy of dexamethasone in reducing arthritic pain and joint swelling can be improved by co-administration of substance P and glutamate receptor antagonists. [ABSTRACT FROM AUTHOR]

Background and Purpose: The mixed-lineage kinases (MLKs) act upstream of mitogen-activated protein kinases, but their role in cardiac biology and pathology is largely unknown.Experimental Approach: We investigated the effect of a MLK1-3 inhibitor CEP-11004 on G protein-coupled receptor agonist-induced stress response in neonatal rat cardiac myocytes in culture.Key Results: CEP-11004 administration dose-dependently attenuated phenylephrine and endothelin-1 (ET-1)-induced c-Jun N-terminal kinase activation. MLK inhibition also reduced ET-1- and phenylephrine-induced phosphorylation of p38 mitogen-activated protein kinase. In contrast, phenylephrine-induced extracellular signal-regulated kinase phosphorylation was further up-regulated by CEP-11004. ET-1 increased activator protein-1 binding activity 3.5-fold and GATA-binding protein 4 (GATA-4) binding activity 1.8-fold, both of which were attenuated with CEP-11004 administration by 59% and 63% respectively. Phenylephrine induced activator protein-1 binding activity by 2.6-fold, which was decreased by 81% with CEP-11004 administration. Phenylephrine also induced a 3.7-fold increase in the transcriptional activity of B-type natriuretic peptide (BNP), which was attenuated by 41% with CEP-11004 administration. In agreement, MLK inhibition also reduced hypertrophic agonist-induced secretion of immunoreactive atrial natriuretic peptide and BNP.Conclusions and Implications: These results showed that inhibition of the MLK1-3 signalling pathway was sufficient for suppressing the activity of key nuclear effectors (GATA-4 and activator protein-1 transcription factors) in cardiac hypertrophy, and attenuated the agonist-induced atrial natriuretic peptide secretion and activation of BNP gene transcription. [ABSTRACT FROM AUTHOR]

Background and Purpose: Sphingosine-1-phosphate and its receptors may be involved in vascular smooth muscle cell (VSMC) proliferation following vascular injury. Here, we evaluate the effect of d-erythro-N,N-dimethylsphingosine (DMS), a sphingosine kinase (SK) inhibitor, on VSMC proliferation, apoptosis and neointimal formation.Experimental Approach: Growth responses in vitro to fetal calf serum (FCS) were measured by [(3)H]-thymidine incorporation and extracellular signal-regulated kinase-1/2 (ERK-1/2) activation in quiescent primary cultures of porcine VSMC in the presence and absence of various concentrations of the SK inhibitor DMS. In vivo treatment with DMS was delivered with a local endoluminal catheter, following balloon injury of coronary arteries. The artery intimal formation was investigated by angiography, myography and histomorphometry.Key Results: In vitro experiments indicated that DMS induced a dose-dependent reduction in [(3)H]-thymidine incorporation and ERK-1/2 activation via a protein kinase C (PKC) independent mechanism with an IC(50) value of 12 +/- 6 and 15 +/- 10 microM respectively. DMS also reduced Akt signalling. Four weeks following in vivo delivery of DMS, complete functional endothelial regeneration was observed in all treatment groups, with significant reduction of intimal formation (vehicle 23.7 +/- 4.6% vs. DMS infusion 8.92 +/- 2.9%, P < 0.05).Conclusions and Implications: Taken together, these results demonstrate that local administration of the SK inhibitor, DMS, reduced neointimal formation, and this effect could involve inhibition of ERK-1/2 and Akt signalling, and modulation of smooth muscle growth. [ABSTRACT FROM AUTHOR]

Background and Purpose: alpha7 Nicotinic receptors have been suggested to play an important role in hippocampal learning and memory. However, the direct action of this receptor subtype on hippocampal pyramidal neurones in vivo has not yet been fully investigated. The availability of selective agonists for alpha7 receptors [AR-R17779 and (R)-(-)-5'-phenylspiro[1-azabicyclo[2.2.2] octane-3,2'-(3'H)furo[2,3-b]pyridine (PSAB-OFP)] has now allowed this role to be investigated.Experimental Approach: Single-cell extracellular recordings were made from hippocampal CA3 pyramidal neurones in anaesthetized rats. The effects of nicotine, AR-R17779 and PSAB-OFP, applied either systemically or iontophoretically, were studied on the activity of these neurones.Key Results: Intravenous injection of cumulative doses of nicotine and PSAB-OFP induced dose-related, significant increases in neuronal firing in the majority of neurones tested. This excitation could be inhibited by intravenous administration of methyllycaconitine (MLA), a selective alpha7 nicotinic receptor antagonist. Furthermore, iontophoretic application of nicotine, AR-R17779 and PSAB-OFP each evoked current-dependent excitation of most CA3 pyramidal neurones studied, and this excitation was antagonized by co-iontophoretic application of MLA. In addition, the excitation induced by iontophoretic application of nicotine, AR-R17779 or PSAB-OFP was also blocked by co-iontophoretic application of either 6,7-dinitroquinoxaline-2,3-dione (DNQX) or D(2)-2-amino-5-phosphonopentanoate (D-AP5), selective N-methyl-D-aspartic acid (NMDA) and non-NMDA receptor antagonists respectively.Conclusions and Implications: CA3 pyramidal neurones are modulated by activation of presynaptic alpha7 nicotinic receptors, which, at least in part, enhances glutamate release onto post-synaptic (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid and NMDA receptors on these CA3 neurones. This mechanism probably contributes to the effects of nicotine on hippocampal learning and memory. [ABSTRACT FROM AUTHOR]

Background and Purpose: The aim of the current study was to investigate the role of arachidonic acid (AA) metabolism via cyclooxygenase (COX) in the endothelial dysfunction of penile arteries from pre-diabetic, obese Zucker rats (OZR).Experimental Approach: Penile arteries from OZR and from lean Zucker rats (LZR) were mounted in microvascular myographs to assess vascular function and COX expression was determined by immunohistochemistry.Key Results: Acetylcholine (ACh) and AA elicited relaxations that were impaired in arteries from OZR. Inhibition of both COX-1 and COX-2 reduced the relaxant effects of ACh and AA in LZR but not in OZR. Inhibitors of COX-1 and of the TXA(2)/PGH(2) (TP) receptor enhanced the relaxations induced by AA in both LZR and OZR, whereas COX-2 inhibition enhanced these responses only in OZR. TP receptor blockade did not restore ACh relaxant responses in arteries from OZR. Inhibition of COX-1 increased basal tension in OZR and this contraction was blunted by TP receptor blockade. The vasoconstrictor responses to noradrenaline were augmented by indomethacin and by COX-2 inhibition in LZR but not in OZR. Immunohistochemical staining showed that both COX-1 and COX-2 are expressed in the endothelium of penile arteries from both LZR and OZR.Conclusions and Implications: Vasoactive prostanoids were formed via constitutively active COX-1 and COX-2 pathways in normal rat penile arteries. Under conditions of insulin resistance, the release and/or effects of vasodilator prostanoids were impaired, contributing to the blunted endothelium-dependent vasodilatation and to the enhanced vasoconstriction. [ABSTRACT FROM AUTHOR]

Background and Purpose: We determined if chronic sympatho-inhibition with rilmenidine has functional significance for the kidney by altering responses of renal blood flow (RBF) and plasma renin activity (PRA) to stress and acute hypotension in rabbits with renovascular hypertension.Experimental Approach: RBF to each kidney and renal sympathetic nerve activity (RSNA) to the left kidney were measured in rabbits in which a renal artery clip induced hypertension (2K1C) and in sham-operated rabbits. After 2 weeks, a subcutaneous minipump was implanted to deliver rilmenidine (2.5 mg.kg(-1).day(-1)) to 2K1C rabbits for 3 weeks.Key Results: After 5 weeks of renal artery stenosis, mean arterial pressure (MAP) was 23% higher and PRA 3-fold greater than in sham-operated rabbits. Blood flow and renal vascular conductance in the stenosed kidney were lower (-75% and -80%) compared with sham, and higher in the non-clipped kidney (68% and 39%). Responses of RBF and PRA to hypotension were similar in 2K1C and sham rabbits. Airjet stress evoked a greater increase in MAP in 2K1C rabbits than sham controls. Chronic rilmenidine normalized MAP, reduced RSNA and PRA, and did not reduce RBF in the stenosed kidney. Responses of RBF (clipped and non-clipped kidney), RSNA and PRA to hypotension and airjet were little affected by rilmenidine.Conclusions and Implications: Our observations suggest that chronic sympatho-inhibition is an effective antihypertensive therapy in renovascular hypertension. It normalizes MAP and reduces basal PRA without compromising blood flow in the stenosed kidney or altering responses of MAP, haemodynamics and PRA to acute hypotension and stress. [ABSTRACT FROM AUTHOR]

Background and Purpose: N-methyl-D-aspartate (NMDA) receptors represent an attractive drug target for the treatment of neurological and neurodegenerative disorders associated with glutamate-induced excitotoxicity. The aim of this study was to map the binding domain of high affinity 5-substituted benzimidazole derivatives [N-{2-[(4-benzylpiperidin-1-yl)methyl]benzimidazol-5-yl}methanesulphonamide (XK1) and N-[2-(4-phenoxybenzyl)benzimidazol-5-yl]methanesulphonamide (XK2)] on the GluN2B subunit of the NMDA receptor.Experimental Approach: The pharmacological antagonistic profiles of XK1 and XK2 were assessed using in vitro rat primary cerebrocortical neurones and two-electrode voltage clamp on Xenopus oocytes expressing heterologous GluN1/GluN2B receptors. Direct ligand binding was determined using the recombinant amino-terminal domain (ATD) of GluN2B.Key Results: XK1 and XK2 effectively protected against NMDA-induced excitotoxicity in rat primary cortical neurones. Low concentrations of XK1 (10 nM) and XK2 (1 nM) significantly reversed neuronal death. Both compounds failed to inhibit currents measured from oocytes heterologously expressing GluN1-1a subunit co-assembled with the ATD-deleted GluN2B subunit. XK1 and XK2 showed specific binding to recombinant protein of GluN2B ATD with low nanomolar affinities. Several residues in the recombinant ATD of GluN2B were identified to be critical for conferring XK1 and XK2 sensitivity. The inhibitory effects of XK1 and XK2 were pH-sensitive, being increased at acidic pH.Conclusions and Implications: These results demonstrate that XK1 and XK2 are effective neuroprotective agents in vitro and indicate that 5-substituted benzimidazole derivatives inhibit GluN1/GluN2B receptors via direct binding to the ATD of the GluN2B subunit. These compounds represent valuable alternatives to the classical antagonist ifenprodil as pharmacological tools for studying GluN2B-containing NMDA receptors. [ABSTRACT FROM AUTHOR]

Background and Purpose: Stimulation of muscarinic receptors in intestinal smooth muscle cells results in suppression of voltage-gated Ca2+ channel currents (I(Ca)). However, little is known about which receptor subtype(s) mediate this effect.Experimental Approach: The effect of carbachol on I(Ca) was studied in single intestinal myocytes from M2 or M3 muscarinic receptor knockout (KO) and wild-type (WT) mice.Key Results: In M2KO cells, carbachol (100 microM) induced a sustained I(Ca) suppression as seen in WT cells. However, this suppression was significantly smaller than that seen in WT cells. Carbachol also suppressed I(Ca) in M3KO cells, but with a phasic time course. In M2/M3-double KO cells, carbachol had no effect on I(Ca). The extent of the suppression in WT cells was greater than the sum of the I(Ca) suppressions in M2KO and M3KO cells, indicating that it is not a simple mixture of M2 and M3 receptor responses. The G(i/o) inhibitor, Pertussis toxin, abolished the I(Ca) suppression in M3KO cells, but not in M2KO cells. In contrast, the G(q/11) inhibitor YM-254890 strongly inhibited only the I(Ca) suppression in M2KO cells. Suppression of I(Ca) in WT cells was markedly reduced by either Pertussis toxin or YM-254890.Conclusion and Implications: In intestinal myocytes, M2 receptors mediate a phasic I(Ca) suppression via G(i/o) proteins, while M3 receptors mediate a sustained I(Ca) suppression via G(q/11) proteins. In addition, another pathway that requires both M2/G(i/o) and M3/G(q/11) systems may be operative in inducing a sustained I(Ca) suppression. [ABSTRACT FROM AUTHOR]

Background and Purpose: Catechol-O-methyltransferase (COMT) metabolizes compounds containing catechol structures and has two forms: soluble (S-COMT) and membrane-bound (MB-COMT). Here we report the generation of a mouse line that expresses MB-COMT but not S-COMT. We compared the effects of deleting S-COMT only or both COMT forms on the pharmacokinetics of oral L-DOPA.Experimental Approach: L-DOPA (10 mg kg(-1)) and carbidopa (30 mg kg(-1)) were given to mice by gastric tube, and samples were taken at various times. HPLC was used to measure L-DOPA in plasma and tissue samples, and dopamine and its metabolites in brain. Immunohistochemistry and Western blotting were used to characterize the distribution of COMT protein isoforms.Key Results: Lack of S-COMT did not affect the levels of L-DOPA in plasma or peripheral tissues, whereas in the full COMT-knock-out mice, these levels were increased. The levels of 3-O-methyldopa were significantly decreased in the S-COMT-deficient mice. In the brain, L-DOPA levels were not significantly increased, and dopamine was increased only in females. The total COMT activity in the S-COMT-deficient mice was 22-47% of that in the wild-type mice. In peripheral tissues, female mice had lower COMT activity than the males.Conclusions and Implications: In S-COMT-deficient mice, MB-COMT in the liver and the duodenum is able to O-methylate about one-half of exogenous L-DOPA. Sexual dimorphism and activity of the two COMT isoforms seems to be tissue specific and more prominent in peripheral tissues than in the brain. [ABSTRACT FROM AUTHOR]

Background and Purpose: The risk for cardiovascular events including venous and arterial disease and stroke is elevated after treatment with estrogen and medroxyprogesterone acetate (MPA) in postmenopausal women. Here, we have investigated the effect of MPA on arterial thrombosis and atherosclerosis in a murine model of atherosclerosis.Experimental Approach: Apolipoprotein E (ApoE)-/- mice were bilaterally ovariectomized and treated with placebo, MPA (27.7 microg day(-1)) and MPA + 17-beta-oestradiol (E2; 1.1 microg day(-1)) for 90 days, on a Western-type diet. Thrombotic response was measured in a photothrombosis model, platelet activation by fluorescence activated cell sorting (FACS) analysis (CD62P) and thrombin generation by the endogenous thrombin potential (ETP). Furthermore, aortic plaque burden and aortic root plaque composition were determined.Key Results: MPA and MPA + E2-treated animals showed an aggravated thrombotic response shown by significantly reduced time to stable occlusion. The pro-thrombotic effect of MPA was paralleled by increased ETP whereas platelet activation was not affected. Furthermore, MPA + E2 reduced the number of cells positive for alpha-smooth muscle actin and increased hyaluronan in the plaque matrix. Interestingly, total plaque burden was reduced by MPA but unchanged by MPA + E2.Conclusion and Implications: Long-term treatment with MPA and MPA + E2 increased arterial thrombosis despite inhibitory effects of MPA on atherosclerosis in ApoE-deficient mice. Increased thrombin formation, reduced smooth muscle content and remodelling of non-collagenous plaque matrix may be involved in the pro-thrombotic effects. Thus, MPA exhibits differential effects on arterial thrombosis and on atherosclerosis. [ABSTRACT FROM AUTHOR]