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Hydrogen sulfide (H2S) is a gasotransmitter employed for intra- and inter-cellular communication in almost all organ systems. This study investigates the role of endogenous H2S in nerve-evoked relaxation of pig terminal bronchioles with 260 μm medium internal lumen diameter. High expression of the H2S synthesis enzyme cystathionine γ-lyase (CSE) in the bronchiolar muscle layer and strong CSE-immunoreactivity within nerve fibers distributed along smooth muscle bundles were observed. Further, endogenous H2S generated in bronchiolar membranes was reduced by CSE inhibition. In contrast, cystathionine β-synthase expression, another H2S synthesis enzyme, however was not consistently detected in the bronchiolar smooth muscle layer. Electrical field stimulation (EFS) and the H2S donor P-(4-methoxyphenyl)-P-4-morpholinylphosphinodithioic acid (GYY4137) evoked smooth muscle relaxation. Inhibition of CSE, nitric oxide (NO) synthase, soluble guanylyl cyclase (sGC) and of ATP-dependent K+, transient receptor potential A1 (TRPA1) and transient receptor potential vanilloid 1 (TRPV1) channels reduced the EFS relaxation but failed to modify the GYY4137 response. Raising extracellular K+ concentration inhibited the GYY4137 relaxation. Large conductance Ca2+-activated K+ channel blockade reduced both EFS and GYY4137 responses. GYY4137 inhibited the contractions induced by histamine and reduced to a lesser extent the histamine-induced increases in intracellular [Ca2+]. These results suggest that relaxation induced by EFS in the pig terminal bronchioles partly involves the H2S/CSE pathway. H2S response is produced via NO/sGC-independent mechanisms involving K+ channels and intracellular Ca2+ desensitization-dependent pathways. Thus, based on our current results H2S donors might be useful as bronchodilator agents for the treatment of lung diseases with persistent airflow limitation, such as asthma and chronic obstructive lung disease.

Aims Neuronal and non-neuronal bradykinin (BK) receptors regulate the contractility of the bladder urine outflow region. The current study investigates the role of BK receptors in the regulation of the smooth muscle contractility of the pig intravesical ureter. Methods Western blot and immunohistochemistry were used to show the expression of BK B1 and B2 receptors and myographs for isometric force recordings. Results B2 receptor expression was consistently detected in the intravesical ureter urothelium and smooth muscle layer, B1 expression was not detected where a strong B2 immunoreactivity was observed within nerve fibers among smooth muscle bundles. On ureteral strips basal tone, BK induced concentration-dependent contractions, were potently reduced by extracellular Ca2+ removal and by B2 receptor and voltage-gated Ca2+ (VOC) channel blockade. BK contraction did not change as a consequence of urothelium mechanical removal or cyclooxygenase and Rho-associated protein kinase inhibition. On 9,11-dideoxy-9a,11a-methanoepoxy prostaglandin F2α (U46619)-precontracted samples, under non-adrenergic non-cholinergic (NANC) and nitric oxide (NO)-independent NANC conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. Kallidin, a B1 receptor agonist, failed to increase preparation basal tension or to induce relaxation on U46619-induced tone. Conclusions The present results suggest that BK produces contraction of pig intravesical ureter via smooth muscle B2 receptors coupled to extracellular Ca2+ entry mainly via VOC (L-type) channels. Facilitatory neuronal B2 receptors modulating NO-dependent or independent NANC inhibitory neurotransmission are also demonstrated.

Introduction: Phosphodiesterase type 5 (PDE5) inhibitors act as effective drugs for the treatment of lower urinary tract symptom (LUTS). There is a poor information, however, about the role of the PDE4 inhibitors on the bladder outflow region contractility. Aim: To investigate PDE4 expression and the relaxation induced by the PDE4 inhibitor rolipram versus that induced by the PDE5 blockers sildenafil and vardenafil, in the pig and human bladder neck. Methods: Immunohistochemistry for PDE4 expression, myographs for isometric force recordings and fura-2 fluorescence for simultaneous measurements of intracellular Ca2+ concentration ([Ca2+]i) and tension for rolipram in bladder neck samples were used. Main Outcome Measures: PDE4 expression and relaxations to PDE4 and PDE5 inhibitors and simultaneous measurements of [Ca2+]i and tension. Results: PDE4 expression was observed widely distributed in the smooth muscle layer of the pig and human bladder neck. On urothelium-denuded phenylephrine (PhE)-precontracted strips of pig and human, rolipram, sildenafil and vardenafil produced concentration-dependent relaxations with the following order of potency: rolipram>>sildenafil>vardenafil. In pig, the adenylyl cyclase activator forskolin potentiated rolipram-elicited relaxation, whereas protein kinase A (PKA) blockade reduced such effect. On potassium-enriched physiological saline solution (KPSS)-precontracted strips, rolipram evoked a lower relaxation than that obtained on PhE-stimulated preparations. Inhibition of large (BKCa) and intermediate (IKCa) conductance Ca2+-activated K+ channels, neuronal voltage-gated Ca2+ channels, nitric oxide (NO) and hydrogen sulfide (H2S) synthases reduced rolipram responses. Rolipram inhibited the contractions induced by PhE without reducing the PhE-evoked [Ca2+]i increase. Conclusions: PDE4 is present in the pig and human bladder neck smooth muscle, where rolipram exerts a much more potent relaxation than that elicited by PDE5 inhibitors. In pig, rolipram-induced response is produced through the PKA pathway involving BKCa and IKCa channel activation and [Ca2+]i desensitization-dependent mechanisms, this relaxation also being due to neuronal NO and H2S release. © 2014 International Society for Sexual Medicine.

Co-activation of NMDA and dopamine receptors is required for the induction of the late phase of LTP (L-LTP) that is dependent on new protein synthesis. Other neuromodulatory substances may also contribute to this process. Here, we examined whether taurine is one of the neuromodulators contributing to L-LTP induction, since it is known that taurine uptake induces a long-lasting synaptic potentiation dependent on protein synthesis, and taurine uptake inhibition blocks L-LTP induced by tetanization. Experiments were conducted using rat hippocampal slices where field synaptic potentials were evoked and recorded in CA3-CA1 synapses. Taurine (1 mM) applied 10 min before a high frequency stimulation (HFS) train converted a transitory early-LTP (E-LTP) into an L-LTP dependent on protein synthesis. This taurine effect was blocked by a taurine uptake inhibitor. A facilitation of L-LTP induction was also obtained by pre-application of SKF38393, a D1/D5 dopamine receptor (D1R) agonist. In this case, LTP facilitation was not affected by the taurine uptake inhibitor. Nevertheless, when taurine and SKF38393 were simultaneously pre-applied at a concentration that individually did not modify E-LTP, they produced a synergistic mechanism that facilitated the induction of L-LTP with a sole HFS train. This facilitation of L-LTP was blocked by inhibiting either taurine uptake or D1R activation. Taurine and SKF38393 activated different signaling pathways to transform E-LTP into L-LTP. Taurine-induced L-LTP facilitation required MAPK activation, while D1R-agonist-induced facilitation depended mainly on PKA activation and partially on MAPK activation. On the other hand, the synergistic mechanisms induced by the cooperative action of taurine and SKF38393 were impaired by inhibitors against MAPK, PKA and PI3-K. This pharmacological profile resembles that displayed by L-LTP induced by three HFS trains at 10-min intervals. These results indicate that taurine uptake is necessary and cooperates with other neurotransmitter systems in the induction of L-LTP.

Because neuronal released endogenous H2S has a key role in relaxation of the bladder outflow region, we investigated the mechanisms involved in H2S dependent inhibitory neurotransmission to the pig bladder neck.Bladder neck strips were mounted in myographs for isometric force recording and simultaneous measurement of intracellular Ca(2+) and tension.On phenylephrine contracted preparations electrical field stimulation and the H2S donor GYY4137 evoked frequency and concentration dependent relaxation, which was reduced by desensitizing capsaicin sensitive primary afferents with capsaicin, and the blockade of adenosine 5'-triphosphate dependent K(+) channels, cyclooxygenase and cyclooxygenase-1 with glibenclamide, indomethacin and SC560, respectively. Inhibition of vanilloid, transient receptor potential A1, transient receptor potential vanilloid 1, vasoactive intestinal peptide/pituitary adenylyl cyclase-activating polypeptide and calcitonin gene-related peptide receptors with capsazepine, HC030031, AMG9810, PACAP6-38 and CGRP8-37, respectively, also decreased electrical field stimulation and GYY4137 responses. H2S relaxation was not changed by guanylyl cyclase, protein kinase A, or Ca(2+) activated or voltage gated K(+) channel inhibitors. GYY4137 inhibited the contractions induced by phenylephrine and by K(+) enriched (80 mM) physiological saline solution. To a lesser extent it decreased the phenylephrine and K(+) induced increases in intracellular Ca(2+).H2S produces pig bladder neck relaxation via activation of adenosine 5'-triphosphate dependent K(+) channel and by smooth muscle intracellular Ca(2+) desensitization dependent mechanisms. H2S also promotes the release of sensory neuropeptides and cyclooxygenase-1 pathway derived prostanoids from capsaicin sensitive primary afferents via transient receptor potential A1, transient receptor potential vanilloid 1 and/or related ion channel activation.

Aims The current study investigates the role played by bradykinin (BK) receptors in the contractility to the pig bladder neck smooth muscle. Methods Bladder neck strips were mounted in myographs for isometric force recordings and BK receptors expression was also determined by immunohistochemistry. Results B2 receptor expression was observed in the muscular layer and urothelium whereas B1 expression was consistent detected in urothelium. A strong B2 immunoreactivity was also observed within nerve fibers among smooth muscle bundles. On urothelium-denuded preparations basal tone, BK induced concentration-dependent contractions which were reduced in urothelium-intact samples, by extracellular Ca2+ removal and by blockade of B2 receptors and voltage-gated Ca2+ (VOC) and non-VOC channels, and increased by cyclooxygenase (COX) inhibition. On phenylephrine-precontracted denuded strips, under non-adrenergic non-cholinergic (NANC) conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. In urothelium-intact samples, the B1 receptor agonist kallidin promoted concentration-dependent relaxations which were reduced by blockade of B1 receptors, COX, COX-1 and large-conductance Ca2+-activated K+ (BKCa) channels and abolished in urothelium-denuded samples and in K+-enriched physiological saline solution-precontracted strips. Conclusions These results suggest that BK produces contraction of pig bladder neck via smooth muscle B2 receptors coupled to extracellular Ca2+ entry via VOC and non-VOC channels with a minor role for intracellular Ca2+ mobilization. Facilitatory neuronal B2 receptors modulating NANC inhibitory neurotransmission and urothelial B1 receptors producing relaxation via the COX-1 pathway and BKCa channel opening are also demonstrated. Neurourol. Urodynam. 33:558–565, 2014. © 2013 Wiley Periodicals, Inc.

Aims There is no information about the signaling pathways involved in the endothelin-1 (ET-1)-induced contraction of bladder neck. The current study investigates the mechanisms involved in the ET-1-elicited contraction in the pig bladder neck. Methods Bladder neck strips were mounted in organ baths containing physiological saline solution at 37°C and gassed with 95% O2 and 5% CO2, for isometric force recording to endothelin receptor agonists, noradrenaline (NA), and electrical field stimulation. Endothelin ETA receptor expression was also determined, by both immunohistochemistry and Western blot. Results ETA receptor expression (Western blot) was observed in the muscular layer and urothelium. A strong ETA-immunoreactivity (ETA-IR) was identified within nerve fibers among smooth muscle bundles. ET-1 and ET-2 evoked similar concentration-dependent contractions of urothelium-denuded preparations. ET-3 produced a slight response, whereas the ETB receptor agonist BQ3020 failed to promote contraction. BMS182874, an ETA receptor antagonist, reduced ET-1-induced contraction whereas BQ788, an ETB antagonist, did not change such responses. ET-1 contractions were reduced by extracellular Ca2+ removal and by inhibition of voltage-gated Ca2+ (VOC) (L-type) and non-VOC channels, Rho/Rho-kinase pathway, and neuronal VOC channels. NA produced contractions which were enhanced by ET-1 threshold concentrations. ETA receptor blockade enhanced nitric oxide-dependent nerve-mediated relaxations. Conclusions These results suggest that ET-1 produces contraction via muscular ETA receptors coupled to extracellular Ca2+ entry via VOC (L-type) and non-VOC channels. Intracellular Ca2+ mobilization and a Rho/Rho-kinase pathway could also be involved in these responses. ET-1-evoked potentiation on noradrenergic contraction, and neuronal ETA receptors modulating nitrergic inhibitory neurotransmission, are also demonstrated. Neurourol. Urodynam. 31:156–161, 2012. © 2011 Wiley Periodicals, Inc.

We studied the role of calcitonin gene-related peptide in nonadrenergic, noncholinergic neurotransmission to the pig bladder neck.We used immunohistochemical techniques to determine the distribution of calcitonin gene-related peptide immunoreactive fibers as well as organ baths for isometric force recording. We investigated relaxation due to endogenously released or exogenously applied calcitonin gene-related peptide in urothelium denuded phenylephrine precontracted strips treated with guanethidine, atropine and NG-nitro-L-arginine to block noradrenergic neurotransmission, muscarinic receptors and nitric oxide synthase, respectively.Rich calcitonin gene-related peptide immunoreactive innervation was found penetrating through the adventitia and distributed in the suburothelial and muscle layers. Numerous, variable size, varicose calcitonin gene-related peptide immunopositive terminals were seen close below the urothelium. In the muscle layer calcitonin gene-related peptide immunopositive nerves usually appeared as varicose terminals running along muscle fibers. Electrical field stimulation (2 to 16 Hz) and exogenous calcitonin gene-related peptide (0.1 nM to 0.3 μM) evoked frequency and concentration dependent relaxation, respectively. Nerve responses were potentiated by capsaicin, decreased by calcitonin gene-related peptide (8-37) and abolished by tetrodotoxin, capsaicin sensitive primary afferent blockers, calcitonin gene-related peptide receptors and neuronal voltage gated Na+ channels. Calcitonin gene-related peptide-induced relaxation was potentiated by the neuronal voltage gated Ca2+ channels blocker ω-conotoxin-GVIA and decreased by calcitonin gene-related peptide (8-37). Calcitonin gene-related peptide relaxation was not modified by blockade of endopeptidases, nitric oxide synthase, guanylyl cyclase and cyclooxygenase.Results suggest that calcitonin gene-related peptide is involved in the nonadrenergic, noncholinergic inhibitory neurotransmission of the pig bladder neck, producing relaxation through neuronal and muscle calcitonin gene-related peptide receptors. Nitric oxide/cyclic guanosine monophosphate and cyclooxygenase pathways do not seem to be involved in such responses.

Benign prostatic hypertrophy has been known to be related with glandular ischemia processes, and nitric oxide (NO) is a potent vasodilator agent. Therefore, the current study investigates the mechanisms underlying the NO-induced vasorelaxation in pig prostatic small arteries. In microvascular myographs, relaxation to electrical field stimulation (EFS), or to exogenous (S)-nitroso-N-acetylpenicillamine (SNAP) and acetylcholine (ACh), was observed on noradrenaline-precontracted prostatic small arterial rings under non-adrenergic and non-cholinergic (NANC) conditions. EFS (1-16 Hz) and exogenous SNAP (0.1-30 μM) evoked frequency- and concentration-dependent relaxation, respectively. Tetrodotoxin, a neuronal voltage-gated Na(+) channel blocker, abolished the EFS-evoked relaxation. ACh (1 nM-10 μM) induced concentration-dependent relaxation, which was reduced by the NO synthase inhibitor N(G)-nitro-L: -arginine (L: -NOARG). L: -NOARG also reduced the EFS-elicited relaxation but failed to modify the response to SNAP. 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and iberiotoxin (IbTX), blockers of soluble guanylyl cyclase and large conductance Ca(2+)-activated K(+) (BK(Ca)) channels, respectively, reduced EFS-, SNAP-, and ACh-induced relaxation. The combination of ODQ with IbTX did not produce further inhibition of the responses to either SNAP or ACh, compared with ODQ alone. Blockade of cyclooxygenases and intermediate and small conductance Ca(2+)-activated, ATP-dependent, and voltage-gated K(+) channels did not change the EFS and SNAP responses. In conclusion, our results suggest that NO and non-NO non-prostanoid factor(s) derived from NANC nerves are involved in the vasodilatation of pig prostatic small arteries. NO produces relaxation through soluble guanylyl cyclase activation-dependent BK(Ca) channel opening and through guanylyl cyclase-independent mechanisms. The vasodilatation elicited by NO could be useful to prevent prostatic ischemia.

Aims The current study investigates the mechanisms involved in nitric oxide (NO)-independent, nonadrenergic, noncholinergic (NANC) inhibitory neurotransmission to the pig urinary bladder neck. Methods Urothelium-denuded strips were mounted in organ baths containing physiological saline solution (PSS) at 37°C for isometric force recordings. The relaxations to electrical field stimulation (EFS) were carried out on strips treated with guanethidine, atropine and NG-nitro-L-arginine, to block noradrenergic neurotransmission, muscarinic receptors and NO synthase, respectively, and precontracted with phenylephrine. Results EFS (1–16 Hz) produced frequency-dependent relaxations which were abolished by the blockade of neuronal voltage-activated Na+ channels. Nonselective and selective inhibition of COX and COX-1, respectively, and blockade of Na+–K+ ATPase reduced the EFS-induced relaxations. However, blockade of COX-2, soluble guanylyl cyclase, large-, intermediate- and small-conductance Ca2+-activated K+ channels, ATP-dependent K+ channels, voltage-gated K+ channels, cAMPc-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) failed to modify the nerve-mediated relaxations. Conclusions The NO-independent inhibitory neurotransmission to the pig urinary bladder neck is mediated, in part, through prostanoids release from a COX-1 pathway, and through activation of the Na+–K+ ATPase. PKA and PKG pathways and postjunctional K+ channels do not appear to be involved in the NO-independent nerve-mediated relaxations. Neurourol. Urodyn. 30:151–157, 2011. © 2010 Wiley-Liss, Inc.

Since endothelin-1 (ET-1) is involved in prostatic disorders, the current study investigated the mechanisms underlying the ET-1-induced effects in pig prostatic small arteries. The experiments were performed in rings mounted in microvascular myographs containing physiological saline solution at 37 o C for isometric force recordings. On basal tension, ET-1 (0.1–30 nM) evoked concentration-dependent contractions, which were enhanced by endothelium removal. ET-1 contractions were inhibited by blockade of endothelin ET A and ET B receptors, extracellular Ca 2+ removal and blockade of voltage-dependent (L-type)- and non-voltage-dependent-Ca 2+ channels. On endothelium intact rings precontracted with noradrenaline, the ET B endothelin receptor agonist BQ3020 promoted a concentration-dependent relaxation which was reduced by blockade of ET B receptors, nitric oxide synthase, guanylyl cyclase and prostanoids synthesis. Endothelium removal abolished its relaxant response and unmasked a BQ3020-induced contraction. Tetraethylammonium and 4-aminopyridine, blockers of non-selective K + channels and voltage-dependent K + (Kv) channels, respectively, inhibited the relaxations to BQ3020. Iberiotoxin, apamin and glibenclamide, blockers of large and small Ca 2+ -activated- and ATP-dependent- K + channels, respectively, failed to modify these responses. These data suggest that ET-1 promotes contraction of pig prostatic small arteries by activating vascular smooth muscle contractile endothelin ET A and ET B receptors coupled to extracellular Ca 2+ entry, via voltage-dependent (L-type)- and non-voltage-dependent Ca 2+ channels, also being due to intracellular Ca 2+ mobilization. In addition, a population of endothelial ET B receptors mediates vasorelaxation via NO-cGMP pathway, vasodilator cyclooxygenase product(s) and Kv channels.

Nitric oxide (NO) is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission of the lower urinary tract. However, functional evidence of this involvement in the human urinary bladder neck has not been consistently demonstrated. Therefore, the current study investigates the relaxations to endogenously released and/or exogenously added NO, in the human bladder neck. Urothelium-denuded bladder neck strips were dissected and mounted in isolated organ baths, containing a physiological saline solution (PSS) at 37 degrees C and continuously gassed with 5% CO(2) and 95% O(2), for isometric force recording. The relaxations to transmural nerve stimulation (EFS) or to exogenously applied NO, as an acidified solution of NaNO(2) were carried out on strips precontracted with phenylephrine, and treated with guanethidine and atropine, to block noradrenergic neurotransmission and muscarinic receptors, respectively. EFS (0.5-16Hz) and exogenous NaNO(2) (1muM to 1mM) evoked frequency- and concentration-dependent relaxations, respectively. The nerve responses were abolished by the blockade of neuronal voltage-activated Na(+) channels with tetrodotoxin, indicating their neurogenic character. N(G)-nitro-l-arginine (l-NOARG), a NO synthase inhibitor, abolished the relaxations to nerve stimulation, which were partially reversed by the substrate of NO synthesis l-arginine. l-NOARG failed to modify the relaxations to exogenous NaNO(2). These results suggest that NO is the major NANC inhibitory neurotransmitter in the human urinary bladder neck. Blockers of NO synthase could be useful in therapy for the urinary incontinence produced by intrinsic sphincteric deficiency.

BACKGROUND AND PURPOSE 5-Hydroxytryptamine (5-HT) is one of the inhibitory mediators in the urinary bladder outlet region. Here we investigated mechanisms involved in 5-HT-induced relaxations of the pig bladder neck. EXPERIMENTAL APPROACH Urothelium-denuded strips of pig bladder were mounted in organ baths for isometric force recordings of responses to 5-HT and electrical field stimulation (EFS). KEY RESULTS After phenylephrine-induced contraction, 5-HT and 5-HT receptor agonists concentration-dependently relaxed the preparations, with the potency order: 5-carboxamidotryptamine (5-CT) > 5-HT = RS67333 > (+/-)-8-hydroxy-2-dipropylaminotetralinhydrobromide > m-chlorophenylbiguanide > alpha-methyl-5-HT > ergotamine. 5-HT and 5-CT relaxations were reduced by the 5-HT(7) receptor antagonist (2R)-1-[(3-hydroxyphenyl)sulphonyl]-2-[2-(4-methyl-1-piperidinyl)ethyl]pyrrolidine hydrochloride and potentiated by (S)-N-tert-butyl-3-(4-(2-methoxyphenyl)-piperazin-1-yl)-2-phenylpropanamide dihydrochloride (WAY 100135) and cyanopindolol, 5-HT(1A) and 5-HT(1A/1B) receptor antagonists respectively. Inhibitors of 5-HT(1B/1D), 5-HT(2), 5-HT(2B/2C), 5-HT(3), 5-HT(4), 5-HT(5A) and 5-HT(6) receptors failed to modify 5-HT responses. Blockade of monoamine oxidase A/B, noradrenergic neurotransmission, alpha-adrenoceptors, muscarinic and purinergic receptors, nitric oxide synthase, guanylate cyclase and prostanoid synthesis did not alter relaxations to 5-HT. Inhibitors of Ca(2+)-activated K(+) and ATP-dependent K(+) channels failed to modify 5-HT responses but blockade of neuronal voltage-gated Na(+)-, Ca(2+)- and voltage-gated K(+) (K(v))-channels potentiated these relaxations. Adenylyl cyclase activation and cAMP-dependent protein kinase (PKA) inhibition potentiated and reduced, respectively, 5-HT-induced responses. Under non-adrenergic, non-cholinergic, non-nitrergic conditions, EFS induced neurogenic, frequency-dependent, relaxations which were resistant to WAY 100135 and cyanopindolol. CONCLUSIONS AND IMPLICATIONS 5-HT relaxed the pig urinary bladder neck through muscle 5-HT(7) receptors linked to the cAMP-PKA pathway. Prejunctional 5-HT(1A) receptors and K(v) channels modulated 5-HT-induced relaxations whereas postjunctional K(+) channels were not involved in such responses. 5-HT(7) receptor antagonists could be useful in the therapy of urinary incontinence produced by intrinsic sphincter deficiency.

Aims Testosterone is beneficial to the cardiovascular system due to its direct coronary vasodilatory action and its circulatory deficiency is associated with coronary artery disease (CAD), which has been proposed as an extrinsic risk factor for benign prostatic hyperplasia (BPH). Therefore, the current study investigated the mechanisms involved in the testosterone-induced vasodilatation in pig prostatic small arteries. Main methods The testosterone vasoactive effects were assessed in small arterial rings mounted in microvascular myographs for isometric force recordings. Key findings Testosterone and the non-aromatizable metabolite 4, 5α-dihydrotestosterone (DHT) evoked a similar concentration-dependent relaxation on noradrenaline (NA)-precontracted rings. Similar responses were obtained in preparations contracted with 60 mM K + -enriched physiological saline solution. Endothelium mechanical removal or pre-treatment with blockers of nitric oxide (NO) synthase, guanylate cyclase, aromatase activity, intracellular androgenic receptor (AR), 5α-reductase, prostanoid synthesis and K + channels, failed to modify the responses to testosterone. In Ca 2+ -free 124 mM KPSS, testosterone markedly inhibited in a concentration-dependent manner the contraction curve t °CaCl 2 . In arteries pretreated with an L-type voltage-activated Ca 2+ channels (VOCCs) inhibitor, nifedipine, testosterone still relaxed noradrenaline-precontracted arteries. Significance These data suggest that testosterone induces a direct vasodilatory action in pig prostatic small arteries independent of either endothelium, NO, prostanoids, aromatase or 5α-reductase activities, AR or K + channels. Such an effect is suggested to be produced via blockade of extracellular Ca 2+ entry through L-type VOCCs and non-L-type Ca 2+ channels. Testosterone-induced vasodilatation could be useful to prevent prostatic ischemia.

Background and purpose: As nitric oxide (NO) plays an essential role in the inhibitory neurotransmission of the bladder neck of several species, the current study investigates the mechanisms underlying the NO-induced relaxations in the pig urinary bladder neck. Experimental approach: Urothelium-denuded bladder neck strips were dissected and mounted in isolated organ baths containing a physiological saline solution at 37 °C and continuously gassed with 5% CO2 and 95% O2, for isometric force recording. The relaxations to transmural nerve stimulation (EFS), or to exogenously applied acidified NaNO2 solution were carried out on strips pre-contracted with phenylephrine, and treated with guanethidine and atropine, to block noradrenergic neurotransmission and muscarinic receptors, respectively. Key results: EFS (0.2–1 Hz) and addition of acidified NaNO2 solution (1 μM–1 mM) evoked frequency- and concentration-dependent relaxations, respectively. These responses were potently reduced by the blockade of guanylate cyclase and were not modified by the K+ channel blockers iberiotoxin, charybdotoxin, apamin or glibenclamide. The voltage-gated K+ (Kv) channels inhibitor 4-aminopyridine, greatly enhanced the nitrergic relaxations evoked by EFS, but did not affect the NaNO2 solution-induced relaxations. Conclusions and implications: NO, whose release is modulated by pre-junctional Kv channels, relaxes the pig urinary bladder neck through a mechanism dependent on the activation of guanylate cyclase, in which post-junctional K+ channels do not seem to be involved. Modulation of Kv channels could be useful in the therapy of the urinary incontinence produced by intrinsic sphincteric deficiency. British Journal of Pharmacology (2008) 153, 1251–1258; doi:10.1038/sj.bjp.0707669; published online 28 January 2008

Aims To investigate the nitric oxide (NO)-mediated nerve relaxation and its possible modulation by pre-junctional α2-adrenoceptors in the pig urinary bladder neck. Methods Urothelium-denuded bladder neck strips were dissected, and mounted in isolated organ baths containing a physiological saline solution (PSS) at 37°C and continuously gassed with 5% CO2 and 95% O2, for isometric force recording. The relaxations to transmural nerve stimulation (electrical field stimulation [EFS]) or exogenously applied NO were carried out on strips pre-contracted with 1 µM phenylephrine (PhE) and treated with guanethidine (10 µM) and atropine (0.1 µM), to block noradrenergic neurotransmission and muscarinic receptors, respectively. Results EFS (0.2–1 Hz, 1 msec duration, 20 sec trains, current output adjusted to 75 mA) evoked frequency-dependent relaxations which were abolished by the neuronal voltage-activated Na+ channel blocker tetrodotoxin (TTX, 1 µM). These responses were potently reduced by the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine (L-NOARG, 30 µM) and further reversed by the NO synthesis substrate L-arginine (L-ARG, 3 mM). The α2-adrenoceptor agonist BHT-920 (2 µM) reduced the electrically evoked relaxations, its effectiveness being higher on the responses induced by low frequency stimulation. BHT-920-elicited reductions were fully reversed by the α2-adrenoceptor antagonist rauwolscine (RAW, 1 µM). Exogenous NO (1 µM–1 mM) induced concentration-dependent relaxations which were not modified by BHT-920, thus eliminating a possible post-junctional modulation. Conclusions These results indicate that NO is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission in the pig urinary bladder neck, the release of NO from intramural nerves being modulated by pre-junctional α2-adrenoceptor stimulation. Neurourol. Urodynam. 26:578–583, 2007. © 2007 Wiley-Liss, Inc.

Background and purpose: As pituitary adenylate cyclase-activating polypeptide 38 (PACAP 38)- and vasoactive intestinal peptide (VIP) are widely distributed in the urinary tract, the current study investigated the receptors and mechanisms involved in relaxations induced by these peptides in the pig bladder neck. Experimental approach: Urothelium-denuded strips were suspended in organ baths for isometric force recordings and the relaxations to VIP and PACAP analogues were investigated. Key results: VIP, PACAP 38, PACAP 27 and [Ala11,22,28]-VIP produced similar relaxations. Inhibition of neuronal voltage-gated Ca2+ channels reduced relaxations to PACAP 38 and increased those induced by VIP. Blockade of capsaicin-sensitive primary afferents (CSPA), nitric oxide (NO)-synthase or guanylate cyclase reduced the PACAP 38 relaxations but failed to modify the VIP responses. Inhibition of VIP/PACAP receptors and of voltage-gated K+ channels reduced PACAP 38 and VIP relaxations, which were not modified by the K+ channel blockers iberiotoxin, charybdotoxin, apamin or glibenclamide. The phosphodiesterase 4 inhibitor rolipram and the adenylate cyclase activator forskolin produced potent relaxations. Blockade of protein kinase A (PKA) reduced PACAP 38- and VIP-induced relaxations. Conclusions and implications: PACAP 38 and VIP relax the pig urinary bladder neck through muscle VPAC2 receptors linked to the cAMP-PKA pathway and involve activation of voltage-gated K+ channels. Facilitatory PAC1 receptors located at CSPA and coupled to NO release, and inhibitory VPAC receptors at motor endings are also involved in the relaxations to PACAP 38 and VIP, respectively. VIP/PACAP receptor antagonists could be useful in the therapy of urinary incontinence produced by intrinsic sphincter deficiency. British Journal of Pharmacology (2006) 149, 100–109. doi:10.1038/sj.bjp.0706832

Taurine application in the CA1 area of rat hippocampal slices induces a long-lasting potentiation of excitatory synaptic transmission that has some mechanistic similitude with the late phase of long-term potentiation (L-LTP). Previous indirect evidence such as temperature and sodium dependence indicated that taurine uptake is one of the primary steps leading to the taurine-induced synaptic potentiation. We show that taurine-induced potentiation is not related to the intracellular accumulation of taurine and is not impaired by 2-guanidinoethanesulphonic acid, a taurine transport inhibitor that is a substrate of taurine transporter. We have found that taurine uptake in hippocampal synaptosomes was inhibited by SKF 89976A, a GABA uptake blocker that is not transportable by GABA transporters. SKF 89976A prevents the induction of synaptic potentiation by taurine application. This effect is neither mimicked by nipecotic acid, a broad inhibitor of GABA transporters that does not affect taurine uptake, nor by NO-711, a specific and potent inhibitor of GABA transporter GAT-1. In addition, L-LTP induced by trains of high-frequency stimulation is also inhibited by SKF 89976A, and taurine, at a concentration that does not change basal synaptic transmission, overcomes such inhibition. We conclude that taurine induces synaptic potentiation through the activation of a system transporting taurine and that taurine uptake is required for the induction of synaptic plasticity phenomena such as L-LTP.

The mechanisms and receptors involved in the vasoactive intestinal peptide (VIP)- and pituitary adenylate cyclase-activating polypeptide (PACAP)-induced relaxations of the pig intravesical ureter were investigated. VIP, PACAP 38 and PACAP 27 concentration-dependently relaxed U46619-contracted ureteral strips with a similar potency. [Ala11,22,28]-VIP, a VPAC1 agonist, showed inconsistent relaxations. The neuronal voltage-gated Ca2+ channel inhibitor, ω-conotoxin GVIA (ω-CgTX, 1 μM), reduced the VIP relaxations. Urothelium removal or blockade of capsaicin-sensitive primary afferents, nitric oxide (NO) synthase and guanylate cyclase with capsaicin (10 μM), NG-nitro-L-arginine (L-NOARG, 100 μM) and 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 5 μM), respectively, did not change the VIP relaxations. However, the PACAP 38 relaxations were reduced by ω-CgTX, capsaicin, L-NOARG and ODQ. The VIP and VIP/PACAP receptor antagonists, [Lys1, Pro2,5, Arg3,4, Tyr6]-VIP (1 μM) and PACAP (6–38) (0.4 μM), inhibited VIP and VIP and PACAP 38, respectively, relaxations. The nonselective and large-conductance Ca2-activated K+ channel blockers, tetraethylammonium (3 mM) and charybdotoxin (0.1 μM), respectively, and neuropeptide Y (0.1 μM) did not modify the VIP relaxations. The small-conductance Ca2-activated K+ channel blocker apamin (1 μM) did not change the PACAP 27 relaxations. The cAMP-dependent protein kinase A (PKA) blocker, 8-(4-chlorophenylthio)adenosine-3′,5′-cyclic monophosphorothioate (Rp-8-CPT-cAMPS, 100 μM), reduced VIP relaxations. The phosphodiesterase 4 inhibitor rolipram and the adenylate cyclase activator forskolin relaxed ureteral preparations. The rolipram relaxations were reduced by Rp-8-CPT-cAMPS. Forskolin (30 nM) evoked a potentiation of VIP relaxations. These results suggest that VIP and PACAP relax the pig ureter through smooth muscle receptors, probably of the VPAC2 subtype, linked to a cAMP-PKA pathway. Neuronal VPAC receptors localized at motor nerves and PAC1 receptors placed at sensory nerves and coupled to NO release, seem also to be involved in the VIP and PACAP 38 relaxations. British Journal of Pharmacology (2004) 141, 123–131. doi:10.1038/sj.bjp.0705582

1 This study was designed to investigate the effect of 5-hydroxytryptamine (5-HT) and to characterize the 5-HT receptors involved in 5-HT responses in the pig intravesical ureter. 2 5-HT (0.01-10 microM) concentration-dependently increased the tone of intravesical ureteral strips, whereas the increases in phasic contractions were concentration-independent. The 5-HT(2) receptor agonist alpha-methyl 5-HT, mimicked the effect on tone whereas weak or no response was obtained with 5-CT, 8-OH-DPAT, m-chlorophenylbiguanide and RS 67333, 5-HT(1), 5-HT(1A), 5-HT(3) and 5-HT(4) receptor agonists, respectively. 5-HT did not induce relaxation of U46619-contracted ureteral preparations. Pargyline (100 microM), a monoaminooxidase A/B activity inhibitor, produced leftward displacements of the concentration-response curves for 5-HT. 3 5-HT-induced tone was reduced by the 5-HT(2) and 5-HT(2A) receptor antagonists ritanserine (0.1 microM) and spiperone (0.2 microM), respectively. However, 5-HT contraction was not antagonized by cyanopindolol (2 microM), SDZ-SER 082 (1 microM), Y-25130 (1 microM) and GR 113808 (0.1 microM), which are respectively, 5-HT(1A/1B), 5-HT(2B/2C), 5-HT(3), and 5-HT(4) selective receptor antagonists. 4 Removal of the urothelium did not modify 5-HT-induced contractions. Blockade of neuronal voltage-activated sodium channels, alpha-adrenergic receptors and adrenergic neurotransmission with tetrodotoxin (1 microM), phentolamine (0.3 microM) and guanethidine (10 microM), respectively, reduced the contractions to 5-HT. However, physostigmine (1 microM), atropine (0.1 microM) and suramin (30 microM), inhibitors of cholinesterase activity, muscarinic- and purinergic P(2)-receptors, respectively, failed to modify the contractions to 5-HT. 5 These results suggest that 5-HT increases the tone of the pig intravesical ureter through 5-HT(2A) receptors located at the smooth muscle. Part of the 5-HT contraction is indirectly mediated via noradrenaline release from sympathetic nerves.

Neuronal and non-neuronal bradykinin (BK) receptors regulate the contractility of the bladder urine outflow region. The current study investigates the role of BK receptors in the regulation of the smooth muscle contractility of the pig intravesical ureter.Western blot and immunohistochemistry were used to show the expression of BK B1 and B2 receptors and myographs for isometric force recordings.B2 receptor expression was consistently detected in the intravesical ureter urothelium and smooth muscle layer, B1 expression was not detected where a strong B2 immunoreactivity was observed within nerve fibers among smooth muscle bundles. On ureteral strips basal tone, BK induced concentration-dependent contractions, were potently reduced by extracellular Ca(2+) removal and by B2 receptor and voltage-gated Ca(2+) (VOC) channel blockade. BK contraction did not change as a consequence of urothelium mechanical removal or cyclooxygenase and Rho-associated protein kinase inhibition. On 9,11-dideoxy-9a,11a-methanoepoxy prostaglandin F2α (U46619)-precontracted samples, under non-adrenergic non-cholinergic (NANC) and nitric oxide (NO)-independent NANC conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. Kallidin, a B1 receptor agonist, failed to increase preparation basal tension or to induce relaxation on U46619-induced tone.The present results suggest that BK produces contraction of pig intravesical ureter via smooth muscle B2 receptors coupled to extracellular Ca(2+) entry mainly via VOC (L-type) channels. Facilitatory neuronal B2 receptors modulating NO-dependent or independent NANC inhibitory neurotransmission are also demonstrated.

The current study was designed to characterize the functionally active tachykinin receptors involved in tachykinin-elicited contractions in the pig intravesical ureter, and to investigate the possible modulation exerted by the natural tachykinins substance P (SP) and neurokinin A (NKA) on the non-adrenergic non-cholinergic (NANC) excitatory ureteral neurotransmission. In pig intravesical ureteral strips pretreated with phosphoramidon (10(-5) mol/L) to block the endopeptidase activities, isometric force recordings showed that SP, NKA, and the NK2 receptor selective agonist [beta-Ala(8)]-NKA (4-10), all three induced contractions, with the following potency order: NKA > [beta-Ala(8) ]-NKA (4-10) > SP. [Sar(9), Met(O(2))(11)]-SP and senktide, selective agonists of the NK1 and NK3 receptors, respectively, failed to modify the ureteral tone. Urothelium removal and incubation with tetrodotoxin (10(-6) mol/L), phentolamine (10(-7) mol/L), propranolol (3 x 10(-6) mol/L), atropine (10(-7) mol/L) and indomethacin (3 x 10(-6) mol/L), did not alter the contraction induced by a submaximal (10(-7) mol/L) dose of [beta-Ala(8)]-NKA (4-10). MEN 10,376 (10(-8)-10(-7) mol/L), a NK2 receptor antagonist, reduced the contraction to 3 x 10(-8) mol/L NKA. GR 82334 (10(-6) -10(-5) mol/L) and SR 142801 (10(-8)-10(-7) mol/L), selective antagonists of the NK1 and NK3 receptors, respectively, did not modify that contraction. In pig intravesical ureteral strips in NANC conditions, SP and NKA induced a potentiation of the contractions to electrical field stimulation (EFS) and to exogenous ATP. The results suggest that the tachykinins evoke a direct contraction of pig intravesical ureteral strips through NK2 receptors located in the smooth muscle. SP and NKA exert an enhancement of the NANC excitatory neurotransmission of the pig intravesical ureter.

Purpose The present investigation was designed to study the role played by neurokinin A (NKA) in the non adrenergic non cholinergic (NANC) neurotransmission of the pig intravesical ureter. Materials and Methods We used immunohistochemical techniques to evidence the distribution of NKA-immunoreactive (NKA-IR) fibers in the pig intravesical ureter. We have also performed isolated organ bath experiments to release endogenous tachykinins from ureteral nerves and to characterize the functionally active receptor through which endogenous ligands evoke contraction, and to show the effect of exogenous tachykinins on intravesical ureteral smooth muscle. Results NKA-IR fibers were found penetrating through ureteral adventitia and distributed in the subepithelial and muscular layers. NKA-IR fibers were not found around small arteries supplying the ureter or in the associated intramural ganglia. Electrical field stimulation (EFS, 1 ms duration, 2 to 16 Hz, 20 s trains) performed in NANC conditions evoked frequency-dependent contractions which were reduced by capsaicin (10 −5 M) and GR 94800 (3 × 10 −8 M), sensory neurotoxin and NK 2 receptor antagonist, respectively. Contractions to EFS were abolished by tetrodotoxin (10 −6 M). Exogenous NKA and substance P (SP) induced dose-dependent contractions, characterized by an increase of the ureteral basal tone, NKA being more potent than SP. Conclusions These results suggest that tachykinins, especially NKA, released from capsaicin-sensitive primary afferents, are involved in the NANC excitatory neurotransmission, contracting the smooth muscle via NK 2 receptors activation, in the pig intravesical ureter. NKA at this level does not seem to participate in the regulation of local blood flow, plasmatic extravasation or ganglionar transmission.

New benzimidazole-4-carboxamides 1-16 and -carboxylates 17-26 were synthesized and evaluated for binding affinity at serotonergic 5-HT4 and 5-HT3 receptors in the CNS. Most of the synthesized compounds exhibited moderate-to-very high affinity (in many cases subnanomolar) for the 5-HT4 binding site and no significant affinity for the 5-HT3 receptor. SAR observations and structural analyses (molecular modeling, INSIGHT II) indicated that the presence of a voluminous substituent in the basic nitrogen atom of the amino moiety and a distance of ca. 8.0 A from this nitrogen to the aromatic ring are of great importance for high affinity and selectivity for 5-HT4 receptors. These results confirm our recently proposed model for recognition by the 5-HT4 binding site. Amides 12-15 and esters 24 and 25 bound at central 5-HT4 sites with very high affinity (Ki = 0.11-2.9 nM) and excellent selectivity over serotonin 5-HT3, 5-HT2A, and 5-HT1A receptors (Ki > 1000-10,000 nM). Analogues 12 (Ki(5-HT4) = 0.32 nM), 13 (Ki(5-HT4) = 0.11 nM), 14 (Ki(5-HT4) = 0.29 nM) and 15 (Ki(5-HT4) = 0.54 nM) were pharmacologically characterized as selective 5-HT4 antagonists in the isolated guinea pig ileum (pA2 = 7.6, 7.9, 8.2 and 7.9, respectively), with a potency comparable to the 5-HT4 receptor antagonist RS 39604 (pA2 = 8.2). The benzimidazole-4-carboxylic acid derivatives described in this paper represent a novel class of potent and selective 5-HT4 receptor antagonists. In particular, compounds 12-15 could be interesting pharmacological tools for the understanding of the role of 5-HT4 receptors.

A test series of 32 phenylpiperazines III with affinity for -5-HT1A and α1 receptors was subjected to QSAR analysis using artificial neural networks (ANNs), in order to get insight into the structural requirements that are responsible for 5- HT 1A α 1 selectivity. Good models and predictive power were obtained for 5-HT1A and α1 receptors. A comparison of these models gives information for the design of the new ligand EF-7412 (5-HT1A: Ki (nM)=27; α1: Ki (nM)> 1000). This derivative displayed affinity for dopamine D2 receptor (Ki=22 nM) and is selective for all other receptor examined (5-HT2A, 5-HT3, 5-HT4 and Bz). EF-7412 acts an antagonist in vivo in pre- and postsynaptic 5-HT1A receptor sites and as an antagonist in dopamine D2 receptor.

1. The present study was designed to characterize the adenosine receptors involved in the relaxation of the pig intravesical ureter, and to investigate the action of adenosine on the non adrenergic non cholinergic (NANC) excitatory ureteral neurotransmission. 2. In U46619 (10(-7) M)-contracted strips treated with the adenosine uptake inhibitor, nitrobenzylthioinosine (NBTI, 10(-6) M), adenosine and related analogues induced relaxations with the following potency order: 5'-N-ethylcarboxamidoadenosine (NECA) = 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA) = 2-chloroadenosine (2-CA) > adenosine > cyclopentyladenosine (CPA) = N6-(3-iodobenzyl)-adenosine-5'-N-methylcarboxamide (IB-MECA) = 2-[p-(carboxyethyl)-phenylethylamino]-5'-N-ethylcarboxamidoaden os ine (CGS21680). 3. Epithelium removal or incubation with indomethacin (3 x 10(-6) M) and L-N(G)-nitroarginine (L-NOARG, 3 x 10(-5) M), inhibitors of prostanoids and nitric oxide (NO) synthase, respectively, failed to modify the relaxations to adenosine. 4. 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 10(-8) M) and 4-(2-[7-amino-2-(2-furyl) [1,2,4]-triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385, 3 x 10(-8) M and 10(-7) M), A1 and A2A receptor selective antagonists, respectively, did not modify the relaxations to adenosine or NECA. 8-phenyltheophylline (8-PT, 10(-5) M) and DPCPX (10(-6) M), which block A1/A2-receptors, reduced such relaxations. 5. In strips treated with guanethidine (10(-5) M), atropine (10(-7) M), L-NOARG (3 x 10(-5) M) and indomethacin (3 x 10(-6) M), both electrical field stimulation (EFS, 5 Hz) and exogenous ATP (10(-4) M) induced contractions of preparations. 8-PT (10(-5) M) increased both contractions. DPCPX (10(-8) M), NECA (10(-4) M), CPCA, (10(-4) M) and 2-CA (10(-4) M) did not alter the contractions to EFS. 6. The present results suggest that adenosine relaxes the pig intravesical ureter, independently of prostanoids or NO, through activation of A2B-receptors located in the smooth muscle. This relaxation may modulate the ureteral NANC excitatory neurotransmission through a postsynaptic mechanism.

The purpose of the present investigation was to clarify whether the hypotensive action of the protoberberine alkaloid, and dopamine receptor antagonist, (-)-stepholidine, can be ascribed to an effect on peripheral small arteries. For this purpose isolated mesenteric small arteries were suspended in microvascular myographs for isometric tension recording. Relaxations mediated by dopamine D1 receptors were antagonized by (-)-stepholidine. (-)-Stepholidine inhibited in a concentration-dependent manner the contractile responses evoked by noradrenaline (10(-6) M), but not the contractile responses evoked by depolarizing solution (KCl, 60 mM) or 9,11-dideoxy-11alpha,9alpha-epoxymethano prostaglandin F2alpha (U46619, 10(-7) M). Mechanical endothelial cell removal, blockade of K+ channels, muscarinic receptors or adrenoceptors did not influence the inhibitory effect of (-)-stepholidine on the contractile response evoked with noradrenaline in the segments. (-)-Stepholidine caused rightward shifts of the concentration-response curves for noradrenaline and phenylephrine. The pA2 values for (-)-stepholidine were 6.05 and 5.94 against noradrenaline and phenylephrine, respectively. Electrical field stimulation induced prazosin-sensitive frequency-dependent contractions in mesenteric small arteries. These contractions were significantly inhibited by 10(-6) and 10(-5) M (-)-stepholidine. In membranes from the rat cerebral cortex labelled with [3H]prazosin, (-)-stepholidine (10(-7)-10(-4) M) completely inhibited the specific binding of the ligand with a pKi of 5.6. The present investigation suggests the inhibitory effect of (-)-stepholidine on the alpha1-adrenoceptor-mediated contractions induced by exogenously added and nerve-released noradrenaline in peripheral small arteries might contribute to a hypotensive effect of the drug.

The alpha-2 receptor antagonist yohimbine has been previously shown to prevent the development of morphine dependence in a rat behavioral model. This study was directed to clarify the mechanism of this interaction, which is presently unknown. Since upregulation of cortical beta-adrenoceptors has been suggested to be involved in morphine withdrawal, we have tested the possible correlation between receptor density and withdrawal behaviors in the presence of yohimbine. Sprague-Dawley male rats received a s.c. suspension of morphine (300 mg/kg) or the vehicle. Animals received saline or yohimbine (4 mg/kg, IP) 24, 28, 48 and 52 h after morphine and finally naloxone (1 mg/kg i.p) at 72 h; the subsequent signs of withdrawal (mainly wet-dog shakes and escape attempts) were recorded and the cerebral cortex dissected to study [3H]-CGP 12177 binding. Morphine-treated animals displayed a marked withdrawal behavior together with beta-adrenoceptor upregulation; nevertheless, these effects were not correlated. As expected, yohimbine prevented morphine withdrawal behavior but did not reverse the beta-adrenoceptor upregulation induced by the opiate. These results confirm previous evidence against the involvement of beta-adrenoceptor upregulation on morphine withdrawal behaviors and also permit to discard beta-adrenoceptor regulation as the neurochemical basis of the antiwithdrawal effect of yohimbine. The possible contribution of some other neurochemical effects of yohimbine are discussed to explain the inhibition of morphine dependence by that drug.

1. The present study was designed to investigate whether potassium (K+) channels are involved in the relaxations to nitric oxide (NO) of pig intravesical ureteral preparations suspended in organ baths for isometric tension recordings. In ureteral strips treated with guanethidine (10-5 M) and atropine (10-7 M) to block adrenergic neurotransmission and muscarinic receptors, respectively, NO was either released from nitrergic nerves by electrical field stimulation (EFS, 0.5-10 Hz, 1 ms duration, 20 s trains), or exogenously-applied as an acidified solution of sodium nitrite (NaNO2, 10-6-10-3 M). 2. Incubation with an inhibitor of guanylate cyclase activation by NO, methylene blue (10-5 M) did not change the basal tension of intravesical ureteral strips but inhibited the relaxation induced by EFS or exogenous NO on ureteral preparations contracted with the thromboxane analogue U46619 (10-7 M). 3. Incubation with charybdotoxin (3 x 10-8 M) and apamin (5 x 10-7 M), which are inhibitors of large and small conductance calcium (Ca2+)-activated K+ channels, respectively, did not modify basal tension or the relaxations induced by EFS and exogenous NO. Treatment with charybdotoxin or apamin plus methylene blue (10-5 M) significantly reduced the relaxations to EFS and exogenous NO. However, in both cases the reductions were similar to the inhibition evoked by methylene blue alone. The combined addition of charybdotoxin plus apamin did not change the relaxations to EFS or exogenously added NO of the porcine intravesical ureter. 4. Cromakalim (10-8-3 x 10-6 M), an opener of ATP-sensitive K+ channels, evoked a dose-dependent relaxation with a pD2 of 7.3 ± 0.2 and maximum relaxant effect of a 71.8 ± 4.2% of the contraction induced by U46619 in the pig intravesical ureter. The blocker of ATP-sensitive K+ channels, glibenclamide (10-6 M), inhibited markedly the relaxations to cromakalim. 5. Glibenclamide (10-6 M) had no effect on the basal tone of ureteral preparations but significantly reduced the relaxations induced by both EFS and exogenous NO. Combined treatment with methylene blue (10-5 M) and glibenclamide (10-6 M) did not exert an effect greater than that of methylene blue alone on either EFS- or NO-evoked relaxations of the pig ureter. 6. The present results suggest that NO acts as an inhibitory neurotransmitter in the pig intravesical ureter and relaxes smooth muscle through a guanylate cyclase-dependent mechanism which seems to favour the opening of glibenclamide-sensitive K+ channels.

The current study investigates the role played by bradykinin (BK) receptors in the contractility to the pig bladder neck smooth muscle.Bladder neck strips were mounted in myographs for isometric force recordings and BK receptors expression was also determined by immunohistochemistry.B2 receptor expression was observed in the muscular layer and urothelium whereas B1 expression was consistent detected in urothelium. A strong B2 immunoreactivity was also observed within nerve fibers among smooth muscle bundles. On urothelium-denuded preparations basal tone, BK induced concentration-dependent contractions which were reduced in urothelium-intact samples, by extracellular Ca(2+) removal and by blockade of B2 receptors and voltage-gated Ca(2+) (VOC) and non-VOC channels, and increased by cyclooxygenase (COX) inhibition. On phenylephrine-precontracted denuded strips, under non-adrenergic non-cholinergic (NANC) conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. In urothelium-intact samples, the B1 receptor agonist kallidin promoted concentration-dependent relaxations which were reduced by blockade of B1 receptors, COX, COX-1 and large-conductance Ca(2+) -activated K(+) (BKCa ) channels and abolished in urothelium-denuded samples and in K(+) -enriched physiological saline solution-precontracted strips.These results suggest that BK produces contraction of pig bladder neck via smooth muscle B2 receptors coupled to extracellular Ca(2+) entry via VOC and non-VOC channels with a minor role for intracellular Ca(2+) mobilization. Facilitatory neuronal B2 receptors modulating NANC inhibitory neurotransmission and urothelial B1 receptors producing relaxation via the COX-1 pathway and BKCa channel opening are also demonstrated. Neurourol. Urodynam. 33:558-565, 2014. © 2013 Wiley Periodicals, Inc.

1. Muscarinic receptors in the pig intravesical ureter were characterized by binding assays in which the muscarinic receptor antagonist, (-)-[3H]-quinuclidinyl benzylate ([3H]QNB) was used as radioligand. 2. The specific binding of [3H]-QNB (about 90% of the total binding, as defined with 10(-5) M unlabelled atropine) was dependent on protein concentration, saturable, and of high affinity (KD = 0.13 +/- 0.02 nM). 3. Displacement of [3H]-QNB specific binding by the M1-selective antagonist, pirenzepine, described a two-component curve, with a minor (17%) high affinity component (pKiH = 8.75), and a major (83%) low affinity one (pKiL = 6.34). The M3-preferential antagonists, hexa-hydro-sila-difenidol (HHSid) and p-fluoro-HHSiD (p-F-HHSiD) delineated also two sites, with pKiH of 8.91 and 8.57 and pKiL of 6.94 and 7.05, respectively. However, the M2-selective antagonists, 11-(2-(diethyl-amino)methyl-1-piperidinylacetyl)-5,11-dihydro-6H-p yrido-(2,3-b)- (1,4)-benzodiazepin-6-one (AF-DX 116, pKi = 6.72) and methoctramine (pKi = 8.34), as well as the M4-selective antagonists, tropicamide (pKi = 7.15) and himbacine (pKi = 8.65) fitted best to a single population of sites. Moreover, 4-diphenyl-acetoxy-N-methyl-piperidine methiodide (4-DAMP), a muscarinic antagonist that discriminates the M1 and M3 versus the M2 subtypes, also delineated one site (pKi = 8.36). 4. The antagonist profile clearly indicates the existence of an M2 population in the porcine intravesical ureter. In addition, the presence of a minor non-M2 population, which may be formed by a mixture of several muscarinic subtypes (i.e. M1, M3 and/or M4) can not be discounted. 5. The present work confirms the results obtained in previous functional studies where the stimulation of muscarinic receptors by carbachol evoked the contraction of the pig isolated intravesical ureter.

We investigated the possible involvement of H2S in nitric oxide independent inhibitory neurotransmission to the pig bladder neck.We used immunohistochemistry to determine the expression of the H2S synthesis enzymes cystathionine γ-lyase and cystathionine β-synthase. We also used electrical field stimulation and myographs for isometric force recordings to study relaxation in response to endogenously released or exogenously applied H2S in urothelium denuded, phenylephrine precontracted bladder neck strips under noradrenergic, noncholinergic, nonnitrergic conditions.Cystathionine γ-lyase and cystathionine β-synthase expression was observed in nerve fibers in the smooth muscle layer. Cystathionine γ-lyase and cystathionine β-synthase immunoreactive fibers were also identified around the small arteries supplying the bladder neck. Electrical field stimulation (2 to 16 Hz) evoked frequency dependent relaxation, which was decreased by DL-propargylglycine and abolished by tetrodotoxin (blockers of cystathionine γ-lyase and neuronal voltage gated Na(+) channels, respectively). The cystathionine β-synthase inhibitor O-(carboxymethyl)hydroxylamine did not change nerve mediated responses. The H2S donor GYY4137 (0.1 nM to 10 μM) induced potent, concentration dependent relaxation, which was not modified by neuronal voltage gated Na(+) channels, or cystathionine γ-lyase or cystathionine β-synthase blockade.Results suggest that endogenous H2S synthesized by cystathionine γ-lyase and released from intramural nerves acts as a powerful signaling molecule in nitric oxide independent inhibitory transmission to the pig bladder neck.

Aims The involvement of endothelin receptors in the contraction of the lower urinary tract smooth muscle is well established. There is scarce information, however, about endothelin receptors mediating relaxation of the bladder outlet region. The current study investigates the possible existence of endothelin ETB receptors involved in the relaxation of pig bladder neck. Methods ETB receptor expression was determined by immunohistochemistry and urothelium-denuded bladder neck strips were mounted in organ baths for isometric force recording. Results ETB-immunoreactivity (ETB-IR) was observed within nerve fibers among smooth muscle bundles and urothelium. BQ3020 (0.01–300 nM), an ETB receptor agonist, produced concentration-dependent relaxations which were reduced by BQ788, an ETB receptor antagonist, and by inhibitors of protein kinase A (PKA) and large (BKCa)- or small (SKCa)-conductance Ca2+-activated K+ channels. Pretreatment with BKCa or SKCa channel inhibitors plus PKA blocking did not cause further inhibition compared with that exerted by inhibiting BKCa or SKCa channels only. BQ3020-induced relaxation was not modified by blockade of either nitric oxide (NO) synthase, guanylyl cyclase, cyclooxygenase (COX) or of intermediate-conductance Ca2+-activated-(IKCa), ATP-dependent-(KATP), or voltage-gated-(Kv) K+ channels. Under non-adrenergic non-cholinergic (NANC) conditions, electrical field stimulation (0.5–16 Hz) evoked frequency-dependent relaxations, which were reduced by BQ788 and potentiated by threshold concentrations of BQ3020. Conclusions These results suggest that BQ3020 produces relaxation of the pig bladder neck via activation of muscle endothelin ETB receptors, NO/cGMP- and COX-independent-, cAMP–PKA pathway-dependent-mechanisms, and involving BKCa and SKCa channel activation. ETB receptors are also involved in the NANC inhibitory neurotransmission. Neurourol. Urodynam. 31:688–694, 2012. © 2012 Wiley Periodicals, Inc.

Benign prostatic hypertrophy has been related with glandular ischemia processes and adenosine is a potent vasodilator agent. This study investigates the mechanisms underlying the adenosine-induced vasorelaxation in pig prostatic small arteries. Adenosine receptors expression was determined by Western blot and immunohistochemistry, and rings were mounted in myographs for isometric force recording. A(2A) and A(3) receptor expression was observed in the arterial wall and A(2A)-immunoreactivity was identified in the adventitia-media junction and endothelium. A(1) and A(2B) receptor expression was not obtained. On noradrenaline-precontracted rings, P1 receptor agonists produced concentration-dependent relaxations with the following order of potency: 5'-N-ethylcarboxamidoadenosine (NECA) = CGS21680 2-Cl-IB-MECA = 2-Cl-cyclopentyladenosine = adenosine. Adenosine reuptake inhibition potentiated both NECA and adenosine relaxations. Endothelium removal and ZM241385, an A(2A) antagonist, reduced NECA relaxations that were not modified by A(1), A(2B), and A(3) receptor antagonists. Neuronal voltage-gated Ca(2+) channels and nitric oxide (NO) synthase blockade, and adenylyl cyclase activation enhanced these responses, which were reduced by protein kinase A inhibition and by blockade of the intermediate (IK(Ca))- and small (SK(Ca))-conductance Ca(2+)-activated K(+) channels. Inhibition of cyclooxygenase (COX), large-conductance Ca(2+)-activated-, ATP-dependent-, and voltage-gated-K(+) channel failed to modify these responses. These results suggest that adenosine induces endothelium-dependent relaxations in the pig prostatic arteries via A(2A) purinoceptors. The adenosine vasorelaxation, which is prejunctionally modulated, is produced via NO- and COX-independent mechanisms that involve activation of IK(Ca) and SK(Ca) channels and stimulation of adenylyl cyclase. Endothelium-derived NO playing a regulatory role under conditions in which EDHF is non-functional is also suggested. Adenosine-induced vasodilatation could be useful to prevent prostatic ischemia.

There is no information about the signaling pathways involved in the endothelin-1 (ET-1)-induced contraction of bladder neck. The current study investigates the mechanisms involved in the ET-1-elicited contraction in the pig bladder neck.Bladder neck strips were mounted in organ baths containing physiological saline solution at 37°C and gassed with 95% O(2) and 5% CO(2) , for isometric force recording to endothelin receptor agonists, noradrenaline (NA), and electrical field stimulation. Endothelin ET(A) receptor expression was also determined, by both immunohistochemistry and Western blot.ET(A) receptor expression (Western blot) was observed in the muscular layer and urothelium. A strong ET(A) -immunoreactivity (ET(A) -IR) was identified within nerve fibers among smooth muscle bundles. ET-1 and ET-2 evoked similar concentration-dependent contractions of urothelium-denuded preparations. ET-3 produced a slight response, whereas the ET(B) receptor agonist BQ3020 failed to promote contraction. BMS182874, an ET(A) receptor antagonist, reduced ET-1-induced contraction whereas BQ788, an ET(B) antagonist, did not change such responses. ET-1 contractions were reduced by extracellular Ca(2+) removal and by inhibition of voltage-gated Ca(2+) (VOC) (L-type) and non-VOC channels, Rho/Rho-kinase pathway, and neuronal VOC channels. NA produced contractions which were enhanced by ET-1 threshold concentrations. ET(A) receptor blockade enhanced nitric oxide-dependent nerve-mediated relaxations.These results suggest that ET-1 produces contraction via muscular ET(A) receptors coupled to extracellular Ca(2+) entry via VOC (L-type) and non-VOC channels. Intracellular Ca(2+) mobilization and a Rho/Rho-kinase pathway could also be involved in these responses. ET-1-evoked potentiation on noradrenergic contraction, and neuronal ET(A) receptors modulating nitrergic inhibitory neurotransmission, are also demonstrated.

The current study investigates the mechanisms involved in nitric oxide (NO)-independent, nonadrenergic, noncholinergic (NANC) inhibitory neurotransmission to the pig urinary bladder neck.Urothelium-denuded strips were mounted in organ baths containing physiological saline solution (PSS) at 37°C for isometric force recordings. The relaxations to electrical field stimulation (EFS) were carried out on strips treated with guanethidine, atropine and N(G) -nitro-L-arginine, to block noradrenergic neurotransmission, muscarinic receptors and NO synthase, respectively, and precontracted with phenylephrine.EFS (1-16 Hz) produced frequency-dependent relaxations which were abolished by the blockade of neuronal voltage-activated Na(+) channels. Nonselective and selective inhibition of COX and COX-1, respectively, and blockade of Na(+) -K(+) ATPase reduced the EFS-induced relaxations. However, blockade of COX-2, soluble guanylyl cyclase, large-, intermediate- and small-conductance Ca(2+) -activated K(+) channels, ATP-dependent K(+) channels, voltage-gated K(+) channels, cAMPc-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) failed to modify the nerve-mediated relaxations.The NO-independent inhibitory neurotransmission to the pig urinary bladder neck is mediated, in part, through prostanoids release from a COX-1 pathway, and through activation of the Na(+) -K(+) ATPase. PKA and PKG pathways and postjunctional K(+) channels do not appear to be involved in the NO-independent nerve-mediated relaxations.

The aim of this paper is to clarify the mechanism through which the taurine analogue guanidinoethane sulfonate (GES) produces its epileptogenic effects. Experiments were performed in the rat hippocampus in vivo, using a brain dialysis probe also containing a recording electrode. Perfusion of 10 mM GES induced an enhancement of extracellular taurine levels probably as a result of forced efflux through the taurine uptake systems in a heteroexchange process. This taurine increase was highly reversible. GES also induced an increase of neuronal excitability and an impairment of recurrent inhibition as judged by the neuronal pattern discharge of evoked potentials. These results indicate the possible implication of GABA receptors in the epileptogenic effect of GES. Specific binding of [3H]-GABA to P2 fractions was inhibited by both bicuculline methiodide (BMI) and GES with the same potency. Similar results were obtained using cerebral sections. Autoradiographic experiments confirm the binding results. GES and BMI completely displaced [3H]-GABA binding. All these results suggest that the epileptogenic GES action is due to a direct antagonism on GABAA receptors.

The current study investigated the distribution of adrenergic nerves and the action induced by noradrenaline (NA) in pig prostatic small arteries. Noradrenergic innervation was visualized using an antibody against dopamine-beta-hydroxylase (DBH), and the NA effect was studied in small arterial rings mounted in microvascular myographs for isometric force recordings. DBH-immunoreactive nerve fibers were located at the adventitia and the adventitia-media border of the vascular wall. Electrical field stimulation (EFS, 1-32 Hz) evoked frequency-dependent contractions that were reduced by guanethidine and prazosin (adrenergic neurotransmission and alpha1-adrenoceptors blockers, respectively) and by the alpha2-adrenoceptor agonist UK 14,304. The alpha2-adrenoceptor antagonist rauwolscine reversed the UK 14,304-produced inhibition. NA produced endothelium-independent contractions that were antagonized with low estimated affinities and Schild slopes different from unity by prazosin and the alpha1A-adrenoceptor antagonist N-[2-(2-cyclopropylmethoxyphenoxy)ethyl]-5-chloro-alpha-alpha-dimethyl-1H-indole-3-ethanamine (RS 17053). The alpha1A-adrenoceptor antagonist 5-methyl-3-[3-[4-[2-(2,2,2,-trifluoroethoxy) phenyl]-1-piperazinyl]propyl]-2,4-(1H)-pyrimidinedione (RS 100329), which also displays high affinity for alpha1L-adrenoceptors, and the alpha1L-adrenoceptor antagonist tamsulosin, which also has high affinity for alpha1A- and alpha1D-adrenoceptors, induced rightward shifts with high affinity of the contraction-response curve to NA. The alpha1D-adrenoceptor antagonist 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]8-azaspiro[4,5]decane-7,9-dione dihydrochloride (BMY 7378) failed to modify the NA contractions that were inhibited by extracellular Ca2+ removal and by voltage-activated (L-type) Ca2+ channel blockade. These data suggest that pig prostatic resistance arteries have a rich noradrenergic innervation; and NA, whose release is modulated by prejunctional alpha2-adrenoceptors, evokes contraction mainly through activation of muscle alpha1L-adrenoceptors coupled to extracellular Ca2+ entry via voltage (L-type)- and non-voltage-activated Ca2+ channels.

To investigate the nitric oxide (NO)-mediated nerve relaxation and its possible modulation by pre-junctional alpha2-adrenoceptors in the pig urinary bladder neck.Urothelium-denuded bladder neck strips were dissected, and mounted in isolated organ baths containing a physiological saline solution (PSS) at 37 degrees C and continuously gassed with 5% CO2 and 95% O2, for isometric force recording. The relaxations to transmural nerve stimulation (electrical field stimulation [EFS]) or exogenously applied NO were carried out on strips pre-contracted with 1 microM phenylephrine (PhE) and treated with guanethidine (10 microM) and atropine (0.1 microM), to block noradrenergic neurotransmission and muscarinic receptors, respectively.EFS (0.2-1 Hz, 1 msec duration, 20 sec trains, current output adjusted to 75 mA) evoked frequency-dependent relaxations which were abolished by the neuronal voltage-activated Na+ channel blocker tetrodotoxin (TTX, 1 microM). These responses were potently reduced by the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine (L-NOARG, 30 microM) and further reversed by the NO synthesis substrate L-arginine (L-ARG, 3 mM). The alpha2-adrenoceptor agonist BHT-920 (2 microM) reduced the electrically evoked relaxations, its effectiveness being higher on the responses induced by low frequency stimulation. BHT-920-elicited reductions were fully reversed by the alpha2-adrenoceptor antagonist rauwolscine (RAW, 1 microM). Exogenous NO (1 microM-1 mM) induced concentration-dependent relaxations which were not modified by BHT-920, thus eliminating a possible post-junctional modulation.These results indicate that NO is involved in the non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission in the pig urinary bladder neck, the release of NO from intramural nerves being modulated by pre-junctional alpha2-adrenoceptor stimulation.

Aims To investigate the role played by pituitary adenylate cyclase activating polypeptide 38 (PACAP 38) in the non-adrenergic non-cholinergic (NANC) neurotransmission of the pig urinary bladder neck. Methods Urothelium-denuded bladder neck strips were dissected and mounted in organ baths containing a physiological saline solution (PSS) at 37°C and gassed with 5% CO2 and 95% O2, for isometric force recording. The relaxations to transmural nerve stimulation (EFS) or PACAP 38 were performed on strips precontracted with 1 µM phenylephrine (PhE). EFS experiments were carried out in the absence and the presence of guanethidine (10 µM), atropine (0.1 µM), and NG-nitro-l-arginine (L-NOARG, 100 µM), to block noradrenergic neurotransmission, muscarinic receptors, and nitric oxide (NO) synthase, respectively. Results EFS (2–16 Hz, 1 ms duration, 20 sec trains, 75 mA current output) evoked frequency-dependent relaxations which were reduced by the VIP/PACAP receptor antagonist PACAP (6–38) (3 µM), and by the neurotoxin of the capsaicin-sensitive primary afferents capsaicin (10 µM), and abolished by the neuronal voltage-activated Na+ channel blocker tetrodotoxin (TTX, 1 µM). The vasoactive intestinal peptide (VIP) receptor antagonist [Lys1, Pro2,5, Arg3,4, Tyr6]-VIP (3 µM) failed to modify the EFS-induced relaxations. PACAP 38 (1 nM–1 µM) induced concentration-dependent relaxations which were reduced by PACAP (6–38), TTX and by the neuronal voltage-gated Ca2+ channel inhibitor ω-conotoxin GVIA (ω-CgTX, 1 µM). Conclusions The results suggest that PACAP 38, mainly released from capsaicin-sensitive primary afferents, is involved in the NANC inhibitory neurotransmission of the pig urinary bladder neck, producing relaxation through neuronal and muscle VIP/PACAP receptor activation. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc.

Our aim was to study the presence of noradrenergic nerves and to characterize the alpha-adrenergic receptors involved in the contractions to electrical field stimulation and to alpha-adrenergic agonists of the horse penile deep dorsal vein. Noradrenergic fibres were visualized by immunohistochemistry using an antibody against dopamine-beta-hydroxylase (DBH). For functional studies, the responses of the venous rings to electrical field stimulation and to alpha-adrenergic agonists (noradrenaline, phenylephrine and BHT 920) were studied in the absence and the presence of noradrenergic transmission- and neuronal sodium channel-blockers (guanethidine and tetrodotoxin, respectively) and of alpha1- and alpha2-adrenergic antagonists (prazosin and rauwolscine, respectively). DBH-immunoreactive fibres were present in the adventitia and in the media layer of the venous rings. Electrical field stimulation (0.5-32 Hz) caused frequency-dependent contractions that were abolished by guanethidine (10(-6) M) and tetrodotoxin (10(-6) M) and reduced by prazosin (10(-9)-10(-7) M) and rauwolscine (3 x 10(-8)-3 x 10(-7) M). Noradrenaline, phenylephrine and BHT 920 induced equipotent contractions of the rings. Prazosin and rauwolscine competitively antagonized the contractions to phenylephrine and BHT 920, respectively. In conclusion, DBH-immunoreactive nerve fibres are present in the horse penile dorsal vein. Both transmural nerve stimulation and alpha-adrenergic agonists induce contraction of the venous rings through a heterogeneous population of alpha1- and alpha2-adrenoceptors.

In the present paper, we report the synthesis and the binding profile on 5-HT1A, alpha 1 and D2 receptors of a new series of imide-arylpiperazines 3. The study of the length of the alkyl chain and the imide substructure allows us to suggest some important differences between the no-pharmacophoric sites of both 5-HT1A and alpha 1-adrenergic receptors, which could be of great importance in order to design new selective ligands.

The purpose of this study was to characterize the pharmacological effects of 2-[[4-(o-methoxyphenyl)piperazin-1-yl]methyl]-1,3-dioxoperhydro imidazo[1,5-a]pyridine (B-20991) by using several biochemical and behavioral assays. Results of binding studies showed that B-20991 binds with high affinity to the 5-HT1A receptor (Ki = 31.7 +/- 1.7 nM), moderate affinity to 5-HT3 receptor (Ki = 269.4 +/- 23.2 nM) and low affinity (Ki1000) to 5-HT2A receptor, dopamine D2 receptor, benzodiazepine receptors and alpha1-adrenoceptor. The administration of B-20991 produced a dose and time related decrease in mouse rectal temperature, increased both lower lip retraction and flat body posture behavioral scores in rat, decreased 5-hydroxytryptamine (5-HT, serotonin) neuronal activity in mouse hypothalamus, and did not alter dopamine neuronal activity nor locomotor activity. The anxiolytic activity of B-20991 was assessed by using both the social interaction and light/dark box tests. The results of these tests indicated that B-20991 caused a dose-related increase in the social interaction and light/dark box behavioral scores. Taken together, these results suggest that B-20991 is a 5-HT1A receptor agonist that exhibits anxiolytic activity.

β-Alanine exerts an inhibitory effect in several experimental preparations. The question whether β-alanine acts through its own receptor or through the γ-aminobutyric acid (GABA) or glycine receptor remains unanswered. Parker et al. (1), based on results obtained using the Xenopus oocyte translation system, proposed a few years ago that β-alanine may have a specific receptor, given the size of β-alanine responses, relative to those of glycine and GABA, as well as the pharmacological profile of β-alanine responses. However, the most recent results point out that β-alanine actions in neurons of the spinal cord are due to an action at the glycine receptor, either the wild-type (2,3) or the mutated one (2,4). In fact, the conclusion of Parker et al. (1) may be criticized on the basis of our experimental design, in which β-alanine antagonism by strychnine or bicuculline, as well as benzodiazepines and barbiturates potentiation of β-alanine responses, were studied with mRNA fractions eliciting responses to both glycine and GABA. Thus the possibility remains that β-alanine acted as a weak agonist for both glycine and GABA receptors. In the present study, using mRNA preparations that elicited responses to just GABA, the β-alanine responses shared their characteristics with those of the GABA responses, strongly suggesting that β-alanine acts through the GABA receptor.

NADPH-diaphorase histochemical staining and electrical field stimulation (EFS) were performed in vitro to investigate whether nitric oxide (NO) is involved in non-adrenergic non-cholinergic (NANC) inhibitory neurotransmission of pig intravesical ureter. NADPH-diaphorase activity was expressed in nerve trunks and thin nerve fibres around arteries and muscular bundles in the intravesical ureter. Relaxations to EFS were tetrodotoxin (10 −6 M)-sensitive which indicates their neurogenic origin. Addition of the NO-synthase inhibitor, l - N G -nitroarginine (L-NOARG, 3 × 10 −5 M), abolished the electrically induced relaxations, which were significantly reversed by l -arginine (3 × 10 −3 M). Addition of acidified sodium nitrite (NaNO 2 , 10 −5 −10 −3 M) evoked concentration-dependent relaxations of ureteral strips which were unaffected by L-NOARG. It is concluded that NO synthase is present in nerve fibres and NO seems to mediate the inhibitory neurotransmission of the porcine intravesical ureter.