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Objective: Several tissues produce and release interleukin‐6 (IL‐6) in response to beta2‐adrenergic stimulation with selective agonists (beta2‐agonists). Moreover, exercise stimulates muscle IL‐6 production, but whether beta2‐agonists regulate skeletal muscle production and release of IL‐6 in humans in association with exercise remains to be clarified. Thus, we investigated leg IL‐6 release in response to beta2‐agonist salbutamol in lean young men at rest and in recovery from resistance exercise. Design: The study employed a randomized controlled crossover design, where 12 men ingested either salbutamol (16 mg) or placebo for 4 days, followed by the last dose (24 mg) administered 1½ h before exercise. Arterial and femoral venous plasma IL‐6 as well as femoral artery blood flow was measured before and ½–5 h in recovery from quadriceps muscle resistance exercise. Furthermore, vastus lateralis muscle biopsies were collected ½ and 5 h after exercise for determination of mRNA levels of IL‐6 and Tumor Necrosis Factor (TNF)‐α. Results: Average leg IL‐6 release was 1.7‐fold higher (p = 0.01) for salbutamol than placebo, being 138 ± 76 and 79 ± 66 pg min−1 (mean ± SD) for salbutamol and placebo, respectively, but IL‐6 release was not significantly different between treatments within specific sampling points at rest and after exercise. Muscle IL‐6 mRNA was 1.5‐ and 1.7‐fold higher (p = 0.001) for salbutamol than placebo ½ and 5 h after exercise, respectively, whereas no significant treatment differences were observed for TNF‐α mRNA. Conclusions: Beta2‐adrenergic stimulation with high doses of the selective beta2‐agonist salbutamol, preceeded by 4 consecutive daily doses, induces transcription of IL‐6 in skeletal muscle in response to resistance exercise, and increases muscle IL‐6 release in lean individuals. [ABSTRACT FROM AUTHOR]

Abstract Omecamtiv mecarbil (OM) is a novel medicine for systolic heart failure, targeting myosin to enhance cardiomyocyte performance. To assist translation to clinical practice we investigated OMs effect on explanted human failing hearts, specifically; contractile dynamics, interaction with the β1–adrenoceptor (AR) agonist (−)‐noradrenaline and spontaneous contractions. Left and right ventricular trabeculae from 13 explanted failing hearts, and trabeculae from 58 right atrial appendages of non‐failing hearts, were incubated with or without a single concentration of OM for 120 min. Time to peak force (TPF) and 50% relaxation (t50%) were recorded. In other experiments, trabeculae were observed for spontaneous contractions and cumulative concentration‐effect curves were established to (−)‐noradrenaline at β1‐ARs in the absence or presence of OM. OM prolonged TPF and t50% in ventricular trabeculae (600 nM, 2 µM, p

Omecamtiv mecarbil (OM) is a novel medicine for systolic heart failure, targeting myosin to enhance cardiomyocyte performance. To assist translation to clinical practice we investigated OMs effect on explanted human failing hearts, specifically; contractile dynamics, interaction with the β1–adrenoceptor (AR) agonist (−)‐noradrenaline and spontaneous contractions. Left and right ventricular trabeculae from 13 explanted failing hearts, and trabeculae from 58 right atrial appendages of non‐failing hearts, were incubated with or without a single concentration of OM for 120 min. Time to peak force (TPF) and 50% relaxation (t50%) were recorded. In other experiments, trabeculae were observed for spontaneous contractions and cumulative concentration‐effect curves were established to (−)‐noradrenaline at β1‐ARs in the absence or presence of OM. OM prolonged TPF and t50% in ventricular trabeculae (600 nM, 2 µM, p <.001). OM had no significant inotropic effect but reduced time dependent deterioration in contractile strength compared to control (p <.001). OM did not affect the generation of spontaneous contractions. The potency of (−)‐noradrenaline (pEC50 6.05 ± 0.10), for inotropic effect, was unchanged in the presence of OM 600 nM or 2 µM. Co‐incubation with (−)‐noradrenaline reduced TPF and t50%, reversing the negative diastolic effects of OM. OM, at both 600 nM and 2 µM, preserved contractile force in left ventricular trabeculae, but imparted negative diastolic effects in trabeculae from human failing heart. (−)‐Noradrenaline reversed the negative diastolic effects, co‐administration may limit the titration of inotropes by reducing the threshold for ischemic side effects. [ABSTRACT FROM AUTHOR]

Objective: The aim of the study was to determine the influence of beta-adrenoceptor (ADRB) antagonists on contractile activity of the nonpregnant human uterus in patients affected by gynecological malignancies.Design: This was a controlled and prospective ex vivo study.Setting: The work was conducted as a collaboration between 4 academic departments.Materials and Methods: Myometrial specimens were obtained from women undergoing hysterectomy for benign gynecological disorders (reference group; N = 15), and ovarian (N = 15), endometrial (N = 15), synchronous ovarian-endometrial (N = 3), and cervical cancer (N = 10). Contractions of myometrial strips in an organ bath before and after applications of ADRB antagonists (propranolol, bupranolol, SR 59230A, and butoxamine) were studied under isometric conditions.Results: Propranolol and bupranolol attenuated contractions in the endometrial and cervical cancer groups similar to that in the reference group (all p < 0.05), whereas opposite effects were observed in the ovarian and synchronous ovarian-endometrial cancer groups. SR 59230A and butoxamine significantly increased contractions in the ovarian cancer group (both p < 0.001).Limitations: These results require now to be placed into a firm clinical context.Conclusions: Our study indicates that ovarian cancer considerably alters contractile activity of the nonpregnant human uterus in response to ADRB antagonists. This suggests a pathogenetic role of beta-adrenergic pathways in this malignancy. Furthermore, propranolol and bupranolol substantially influence spontaneous uterine contractility. [ABSTRACT FROM AUTHOR]

While studies have demonstrated substantial differences in beta2‐adrenergic agonist enantiomer pharmacology, enantioselective disposition of long‐acting beta2‐adrenergic ligand racemic (rac)‐formoterol in blood is inadequately explored after inhaled therapy given analytical challenges. Furthermore, information on enantioselective disposition and partitioning of beta2‐adrenergic agonist in skeletal muscle is absent despite its promising data on muscle anabolism in humans. Using a sensitive ultra‐high performance liquid chromatography−mass spectrometry (UPLC−MS/MS) assay, we determined disposition of (R,R)‐formoterol and (S,S)‐formoterol in plasma and skeletal muscle samples from 11 non‐asthmatic men who had inhaled rac‐formoterol at therapeutic doses (2 × 27 μg). Mean (SD) concentrations of (R,R)‐ and (S,S)‐formoterol in plasma and in muscle biopsies of the vastus lateralis 1 hour after inhalation of formoterol were 31 (15) and 45 (18) pg × mL−1 for (R,R)‐formoterol and (S,S)‐formoterol, respectively, in plasma, and 0.56 (0.32) and 0.51 (0.29) pg × mgwet wt−1, respectively, in muscle. Formoterol exhibited different enantioselective disposition in plasma and muscle (p < 0.0001). In plasma, mean log (R,R):(S,S)‐formoterol ratio was lower than 0 [−0.17(0.07), p < 0.0001], whereas in muscle, mean log (R,R):(S,S)‐formoterol ratio was slightly higher than 0 [0.04(0.07), p < 0.05]. Log (R,R):(S,S)‐formoterol ratio in muscle was related to muscle fiber‐type composition. Furthermore, formoterol induced an approximately two‐fold increase in muscle p‐PKASer/thr phosphorylation (p < 0.01), indicating a substantial beta2‐adrenergic response. Collectively, these findings suggest that formoterol exhibits modest enantioselective disposition in plasma after inhaled therapy in humans, which appear related to a greater (R,R)‐enantiomer disposition in skeletal muscle that may be dependent on fiber‐type composition. [ABSTRACT FROM AUTHOR]

Senescent hearts exhibit defective responses to β-adrenergic receptor (β- AR) over-activation upon stress, leading to more severe pathological cardiac remodelling. However, the underlying mechanisms remain unclear. Here, we investigated the role of adenosine monophosphate-activated protein kinase ( AMPK) in protecting against ageing-associated cardiac remodelling in mice upon β- AR over-activation. 10-week-old (young) and 18-month-old (old) mice were subcutaneously injected with the β- AR agonist isoproterenol ( ISO; 5 mg/kg). More extensive cardiac fibrosis was found in old mice upon ISO exposure than in young mice. Meanwhile, ISO treatment decreased AMPK activity and increased β-arrestin 1, but not β-arrestin 2, expression, and the effects of ISO on AMPK and β-arrestin 1 were greater in old mice than in young mice. Similarly, young AMPKα2-knockout ( KO) mice showed more extensive cardiac fibrosis upon ISO exposure than that was observed in age-matched wild-type ( WT) littermates. The extent of cardiac fibrosis in WT old mice was similar to that in young KO mice. Additionally, AMPK activities were decreased and β-arrestin 1 expression increased in KO mice. In contrast, the AMPK activator metformin decreased β-arrestin 1 expression and attenuated cardiac fibrosis in both young and old mice upon ISO exposure. In conclusion, more severe cardiac fibrosis is induced by ISO in old mice than in young mice. A decrease in AMPK activity, which further increases β-arrestin 1 expression, is the central mechanism underlying the ageing-related cardiac fibrosis induced by ISO. The AMPK activator metformin is a promising therapeutic agent for treating ageing-related cardiac remodelling upon β- AR over-activation. [ABSTRACT FROM AUTHOR]

Clenbuterol (CB), a selective β2-adrenergic receptor (AR) agonist, induces muscle hypertrophy and counteracts muscle atrophy. However, it is paradoxically less effective in slow-twitch muscle than in fast-twitch muscle, though slow-twitch muscle has a greater density of β-AR. We recently demonstrated that Epac1 (exchange protein activated by cyclic AMP [cAMP]1) plays a pivotal role in β2-AR-mediated masseter muscle hypertrophy through activation of the Akt and calmodulin kinase II (CaMKII)/histone deacetylase 4 (HDAC4) signaling pathways. Here, we investigated the role of Epac1 in the differential hypertrophic effect of CB using tibialis anterior muscle (TA; typical fast-twitch muscle) and soleus muscle (SOL; typical slow-twitch muscle) of wild-type (WT) and Epac1-null mice (Epac1KO). The TA mass to tibial length (TL) ratio was similar in WT and Epac1KO at baseline and was significantly increased after CB infusion in WT, but not in Epac1KO. The SOL mass to TL ratio was also similar in WT and Epac1KO at baseline, but CB-induced hypertrophy was suppressed in both mice. In order to understand the mechanism involved, we measured the protein expression levels of β-AR signaling-related molecules, and found that phosphodiesterase 4 (PDE4) expression was 12-fold greater in SOL than in TA. These results are consistent with the idea that increased PDE4-mediated cAMP hydrolysis occurs in SOL compared to TA, resulting in a reduced cAMP concentration that is insufficient to activate Epac1 and its downstream Akt and CaMKII/HDAC4 hypertrophic signaling pathways in SOL of WT. This scenario can account for the differential effects of CB on fast- and slow-twitch muscles. [ABSTRACT FROM AUTHOR]

The alpha2 Heremans-Schmid glycoprotein (AHSG) gene is implicated in the regulation of body fat and insulin sensitivity. The Met/Met genotype of the common single-nucleotide polymorphism (SNP), rs4917, in the AHSG gene has been shown to be associated with reduced plasma levels as well as lower body fat. Here, we studied the association of this variation with subcutaneous adipocyte lipolysis. Ninety-three obese and nonobese healthy men were genotyped for Thr230Met, and subcutaneous adipose tissue biopsies were analyzed for lipolysis characteristics. The Met/Met genotype was associated with a marked increase of 1.5 log units in the lipolytic sensitivity to the β2-adrenoceptor agonist terbutaline (P = 0.0008) as compared with the Thr/Thr and Thr/Met genotypes. This corresponds to an approximately 35-fold increase in β2-adrenoceptor function. The genotype effect was independent of body mass index and waist circumference. In contrast, lipolytic sensitivity to both the β1-adrenoceptor agonist dobutamine (P = 0.25) and the α2A-adrenoceptor agonist clonidine (P = 0.54) was unaffected by the Thr230Met variation. Moreover, no difference in either maximal stimulation or inhibition of lipolysis was found between genotypes.We conclude that a common variation (Thr230Met) in the AHSG gene is associated with a marked increase in β2-adrenoceptor sensitivity in subcutaneous fat cells, which may be of importance in body weight regulation.

Background and purpose The early management of the cardiovascular dysfunction of septic shock is critical as it is associated with a poor outcome. Although the use of catecholamines is a common therapy in this syndrome, no data are available on the involvement of β-adrenoceptor (β-AR) subtypes and only few studies report an alteration of β-adrenergic-induced vasodilation in septic shock. The purpose of the study was to evaluate vascular β 1 , β 2 and β 3 -AR expression and function in an endotoxemic rat model. Experimental approach Endotoxemia was induced in rats by intravenous injection of lipopolysaccharide (LPS). β 1 , β 2 and β 3 -AR mRNA expression was evaluated by RT-PCR in aorta and vascular β 1 , β 2 and β 3 -AR responses were determined on conducting (aorta) and/or resistance (mesenteric and renal) arteries by constructing relaxation curves in response to different β-AR agonists. Results The maximal effect of isoproterenol decreased by 31 to 61% in the three vascular beds of LPS-treated rats compared to controls. In aortas from LPS-treated rats, β 1 and β 3 -AR mRNA expression was decreased and associated to a reduced β 1 and β 3 -induced vasodilation. Conversely, albeit β 2 -AR mRNA was unchanged, the maximal β 2 -AR-induced vasodilation increased by 49% in aortas from LPS-treated rats compared to controls. This increase was not affected by endothelium removal but was abolished in the presence of a β 2 -AR antagonist or an adenylate cyclase inhibitor. Conclusions In endotoxemia, β 2 -AR vasodilation was increased by a potential recruitment of β 2 -AR located on smooth muscle cells. This study suggests that vascular β 2 -AR should be a putative new therapeutic target in septic shock. [ABSTRACT FROM AUTHOR]

The study was a randomized placebo-controlled trial investigating mechanisms by which chronic β2-adrenergic stimulation enhances muscle force and power output during maximal cycle ergometer exercise in young men. Eighteen trained men were assigned to an experimental group [oral terbutaline 5 mg/30 kg body weight (bw) twice daily (TER); n = 9] or a control group [placebo (PLA); n = 9] for a 4-wk intervention. No changes were observed with the intervention in PLA. Isometric muscle force of the quadriceps increased (P ≤0.01) by 97 ± 29 N (means SE) with the intervention in TER compared with PLA. Peak and mean power output during 30 s of maximal cycling increased (P ≤ 0.01) by 32 ± 8 and 25 ± 9 W, respectively, with the intervention in TER compared with PLA. Maximal oxygen consumption (VO2max) and time to fatigue during incremental cycling did not change with the intervention. Lean body mass increased by 1.95 ± 0.8 kg (P ≤ 0.05) with the intervention in TER compared with PLA. Change in single fiber cross-sectional area of myosin heavy chain (MHC) I (1,205 ± 558 µm² ; P ≤0.01) and MHC II fibers (1,277 ± 595m ; P ≤ 0.05) of the vastus lateralis muscle was higher for TER than PLA with the intervention, whereas no changes were observed in MHC isoform distribution. Expression of muscle proteins involved in growth, ion handling, lactate production, and clearance increased (P ≤ 0.05) with the intervention in TER compared with PLA, with no change in oxidative enzymes. Our observations suggest that muscle hypertrophy is the primary mechanism underlying enhancements in muscle force and peak power during maximal cycling induced by chronic β2-adrenergic stimulation in humans. [ABSTRACT FROM AUTHOR]

The results of many studies suggested possible relationship between polymorphism at codons 16 and 27 and development of tolerance to beta-2 adrenoceptor agonist responses as well as disease severity in asthmatic patients. This study was designed to evaluate the effect of polymorphism of beta2 adrenoceptors on response to salmeterol and fluticasone (as inhaled Seretide). Sixty-four patients with either mild or moderate-severe asthma were evaluated in this study. A four-week therapy with Seretide was conducted in moderate-severe asthmatics. The respiratory parameters and asthma score (based on GINA guidelines) were measured before and after run in period. Blood samples were genotyped at codons 16 and 27. No significant difference was observed in genotypes neither at codon 16 nor at codon 27 between mild and moderate-severe asthma groups. However, Patients in Arg/Arg (n = 8) category showed significant improvement in asthma control parameters and lung function compared with Arg/Gly genotype (n =20). These results suggest that genotyping may be useful in some asthmatic patients in order to better tailor asthma treatment plan.

Downregulation of endothelial connexins has been shown to result in impaired angiogenesis. Isoprenaline is known to upregulate Cx43 in cardiomyocytes. Effects of isoprenaline on endothelial connexins are unknown. We wanted to investigate whether isoprenaline might induce upregulation of connexins Cx37, Cx40, or Cx43 in human endothelial cells and whether it may promote angiogenesis. Human umbilical vein endothelial cells (HUVECs) were cultured until confluence (5 days) and subsequently seeded in Matrigel in vitro angiogenesis assays for 18 h. During the entire cell culture and angiogenesis period, cells were treated with vehicle or isoprenaline (100 nM). Finally, the resulting angiogenetic network was investigated (immuno)histologically. Moreover, expression of Cx37, Cx40, and Cx43 was determined by Western blot. In addition, we measured functional intercellular gap junction coupling by dye injection using patch clamp technique. Isoprenaline resulted in significantly enhanced expression of endothelial Cx43 and to a lower degree of Cx40 and Cx37. The number of coupling cells was significantly increased. Regarding angiogenesis, we observed significantly enhanced formation of branches and a higher complexity of the tube networks with more branches/length. Isoprenaline increases endothelial connexin expression and intercellular coupling and promotes tube formation. [ABSTRACT FROM AUTHOR]

Aims Noradrenaline plays an important role in the modulation of atrial electrophysiology. However, the identity of the modulated channels, their mechanisms of modulation, and their role in the action potential remain unclear. This study aimed to investigate the noradrenergic modulation of an atrial steady-state outward current (IKss). Methods and results Rat atrial myocyte whole-cell currents were recorded at 36°C. Noradrenaline potently inhibited IKss (IC50 = 0.90 nM, 42.1 ± 4.3% at 1 µM, n = 7) and potentiated the L-type Ca2+ current (ICaL, EC50 = 136 nM, 205 ± 40% at 1 µM, n = 6). Noradrenaline-sensitive IKss was weakly voltage-dependent, time-independent, and potentiated by the arachidonic acid analogue, 5,8,11,14-eicosatetraynoic acid (EYTA; 10 µM), or by osmotically induced membrane stretch. Noise analysis revealed a unitary conductance of 8.4 ± 0.42 pS (n = 8). The biophysical/pharmacological properties of IKss indicate a TREK-like K+ channel. The effect of noradrenaline on IKss was abolished by combined β1-/β2-adrenoceptor antagonism (1 µM propranolol or 10 µM β1-selective atenolol and 100 nM β2-selective ICI-118,551 in combination), but not by β1- or β2-antagonist alone. The action of noradrenaline could be mimicked by β2-agonists (zinterol and fenoterol) in the presence of β1-antagonist. The action of noradrenaline on IKss, but not on ICaL, was abolished by pertussis toxin (PTX) treatment. The action of noradrenaline on ICaL was mediated by β1-adrenoceptors via a PTX-insensitive pathway. Noradrenaline prolonged APD30 by 52 ± 19% (n = 5; P < 0.05), and this effect was abolished by combined β1-/β2-antagonism, but not by atenolol alone. Conclusion Noradrenaline inhibits a rat atrial TREK-like K+ channel current via a PTX-sensitive mechanism involving co-operativity of β1-/β2-adrenoceptors that contributes to atrial APD prolongation. [ABSTRACT FROM PUBLISHER]

The β2-adrenergic receptor (β2AR) is the prototypic member of G protein-coupled receptors (GPCRs) involved in the production of physiological responses to adrenaline and noradrenaline. Research done in the past few years vastly demonstrated that β2AR can form homo- and hetero-oligomers. Despite the fact that currently this phenomenon is widely accepted, the spread and relevance of β2AR oligomerization are still a matter of debate. This review considers the progress achieved in the field of β2AR oligomerization with focus on the implications of the receptor-receptor interactions to β2AR trafficking, pharmacology and downstream signal transduction pathways. [ABSTRACT FROM AUTHOR]

The results of many studies suggested possible relationship between polymorphism at codons 16 and 27 and development of tolerance to beta-2 adrenoceptor agonist responses as well as disease severity in asthmatic patients. This study was designed to evaluate the effect of polymorphism of beta2 adrenoceptors on response to salmeterol and fluticasone (as inhaled Seretide). Sixty-four patients with either mild or moderate-severe asthma were evaluated in this study. A four-week therapy with Seretide was conducted in moderate-severe asthmatics. The respiratory parameters and asthma score (based on GINA guidelines) were measured before and after run in period. Blood samples were genotyped at codons 16 and 27. No significant difference was observed in genotypes neither at codon 16 nor at codon 27 between mild and moderate-severe asthma groups. However, Patients in Arg/Arg (n = 8) category showed significant improvement in asthma control parameters and lung function compared with Arg/Gly genotype (n =20). These results suggest that genotyping may be useful in some asthmatic patients in order to better tailor asthma treatment plan. [ABSTRACT FROM AUTHOR]

The effects of noradrenaline (NA) on inhibitory responses to gamma aminobutyric acid (GABA) in neurones of the deep cerebellar nuclei were studied in vivo in rats, using extracellular single-unit recordings and microiontophoretic drug application. NA application altered GABA-evoked responses in 95 % of the neurones tested, but the effects differed between nuclei. Application of NA depressed GABA responses in the medial (MN) and posterior interpositus (PIN) nuclei, but enhanced GABA responses in the anterior interpositus nucleus (AIN). Comparable proportions of enhancing (57 %) and depressive (43 %) effects were found in the lateral nucleus (LN). The alpha noradrenergic receptor agonist clonidine mimicked the depressive effect of NA on GABA responses in MN and PIN and its enhancing effects in AIN and LN, while the alpha antagonist yohimbine partially blocked these effects. The beta-adrenergic agonist isoproterenol and antagonist timolol respectively induced and partially blocked enhancements of GABA responses in all nuclei except for LN, where isoproterenol had a weak depressive effect. It is concluded that NA modulates GABA responses by acting on both alpha and beta receptors. Activation of these receptors appears to be synergistic in the AIN and opposite in the remaining deep nuclei. These results support the hypothesis that the noradrenergic system participates in all the regulatory functions involving the cerebellum in a specific and differential manner, and suggest that any change in NA content, as commonly observed in ageing or stress, could influence cerebellar activity. [ABSTRACT FROM AUTHOR]

Clenbuterol is a long-lasting β-adrenoceptor (β-AR) agonist and was once medicated as a bronchial dilatator, and is also used by body-building enthusiasts and athletes and in livestock breeding because of its anabolic effect on skeletal muscles and ability to promote lipolysis. Though prohibited from pharmacological uses, clenbuterol intoxication cases are frequently reported, and most of the cardiac symptoms are tachyarrhythmia. Here, we reported a different cardiovascular toxic response to clenbuterol. Using a rabbit model, we tested the dose-response pattern of the cardiovascular system to intravenous administration of clenbuterol. Routine arterial blood pressure (BP) and surface electrocardiogram (ECG) were monitored. We observed that clenbuterol at a lower dose (0.4 mg/kg, n = 3) did not significantly affect the ECG, but decreased the mean BP roughly by 15-18 mmHg. At a medial dose (3.6 mg/kg, n = 3), clenbuterol induced significant hypotension (mean BP dropped by about 30 mmHg), first-degree atrioventricular (AV) block and intermittent ectopic activities with a relatively slow rate. The hypotension and arrhythmia recovered slowly, and animals did not die. Higher-dose clenbuterol (10 mg/kg, n = 6) induced severe hypotension, second-degree AV block (Mobitz type II), 2:1 ventricular capture and progressive prolongations of P-R intervals and QRS duration, and the animals soon died of cardiac asystole. Different from other reports, we had not observed lethal tachyarrhythmia in all experiments except for the slight heart rate acceleration during the recovery stage of medial clenbuterol dosage. These results indicate that acute intravenous administration of clenbuterol has serious, dose-dependent cardiovascular toxicities and is even life threatening. [ABSTRACT FROM AUTHOR]

Glycine allele at codon 16 has previously been associated with the increase in asthma severity, bronchial hyperresponsiveness and also the increase in inhaled corticosteroid dependence. This study was designed to evaluate the genetic alleles in mild asthma. Thirty-four patients with diagnosis of mild asthma (FEV1 ⩾ 80%, positive methacholine test) and body mass index (BMI ⩽ 30 Kg/m²) were included in the study. They could only use short acting beta-2 agonists for asthma control. Smoking, infection, occupational sensitizers' exposure, gastroesophageal reflux, diabetes mellitus and heart failure were also considered as exclusion criteria. All patients were genotyped at 16th and 27th codons. Among all, 20 (58.8%) Arg/Gly, 14 (41.2%) Arg/Arg and no Gly/Gly genotype were detected at codon 16. Genotyping at codon 27 revealed 2 (5.9%) Glu/Glu, 13 (38.2%) Glu/Gln and 18 Gln/Gln (52.9%). Based on the obtained results, Arg/Gly mutation had a higher rate among the studied subjects compared to Arg/Arg polymorphism. This is a pilot study which shows a probable usefulness of genotyping for predicting of asthma severity. [ABSTRACT FROM AUTHOR]

Abstract: Psychological stress leads to sympathetically mediated increases in body temperature. Brown adipose tissue (BAT) is often thought to be the main organ to produce heat in response to sympathetic activation. However, we have previously shown that the hyperthermia evoked by conditioned fear in rats is not the result of thermogenesis in the interscapular area of the back, where the largest deposit of BAT is found. Stress-induced hyperthermia is widely used as an anxiety indicator in mice. We thus sought to verify if this response can be attributed to BAT thermogenesis. Eight C57BL/6 mice were shaved in the interscapular and lumbar back areas prior to testing. Animals received injections of 20mg/kg dl-propranolol or saline and were placed in either an open field or 4°C enclosure for 30min. Infrared thermographic images were taken each minute to record interscapular, lumbar and tail skin temperatures. Propranolol reduced the stress-induced hyperthermia observed during open field exposure (p<0.01), as indicated by the lumbar back skin temperature. Nevertheless, the difference between interscapular and lumbar skin temperatures remained constant, suggesting that this hyperthermia was not caused by BAT thermogenesis. There was no observable effect of propranolol on behavior, as animals remained active throughout the test. In contrast, the difference between interscapular and lumbar back skin temperature was increased by 2°C during cold exposure. This increase was abolished after propranolol (p<0.001), indicating BAT thermogenesis during this challenge. Hence, just as rats exposed to conditioned fear, mice exposed to an open field display a stress-induced hyperthermia that is not caused by BAT thermogenesis. [Copyright &y& Elsevier]

Our study aimed to elucidate whether bone marrow stem cell (BMC) treatment might result in a cellular response in cardiomyocytes in vitro. Subconfluent neonatal rat cardiomyocyte cultures were cocultured for three days with Vybrant CM‐DiI labeled BMC from human sternal bone marrow and underwent immunohistological staining for the proto-oncogene c-Myc and the cell cycle proteins CDK2, CDK4 and ATF-3. β-adrenoceptor density was analyzed using [125I]-iodocyanopindolol (ICYP) histoautoradiography. Quantitative analysis of immunohistochemical images revealed significantly increased expression and upregulation of c-Myc, and its downstream targets ATF-3, CDK2 and CDK4 in neighboring cardiomyocytes to BMC, depending on their distance to the BMC compared to cardiomyocytes far from the BMC. Histoautoradiography revealed a significantly higher β-adrenoceptor density in cardiomyocytes in the immediate vicinity to the BMC. With increasing distance to the BMC, β-adrenoceptor density in cardiomyocytes declined. Thus, a small number of BMC can affect a larger number of cardiomyocytes by activating an intracellular signaling cascade and enhancing β-adrenoceptor density. [ABSTRACT FROM AUTHOR]

Abstract: In the heart the most prominent cardiac gap junction protein is connexin43 (Cx43). Increased Cx43 expression has been identified in cardiac hypertrophy and may contribute to arrhythmias. Besides acute effects on gap junction channel function, chronic regulation of Cx43 expression can affect intercellular communication. Since both cyclic mechanical stretch (CMS) and catecholamines play an important role in cardiac physiology and pathophysiology, we wanted to elucidate whether a prolonged β- or α-adrenoceptor stimulation may modulate the effects of CMS on Cx43 expression. Neonatal rat cardiomyocytes were cultured on flexible 6-well plates. Thereafter, cells were kept static without any treatment or stimulated with 0.1μmol/L isoprenaline or phenylephrine for 24h without or with additional CMS (1Hz; 10% elongation). Isoprenaline and phenylephrine given alone significantly increased Cx43-protein and -mRNA level. Also CMS resulted in a significant Cx43-protein and -mRNA up-regulation. The combined treatment of the cells with either isoprenaline or phenylephrine and stretch also resulted in an up-regulation of Cx43-protein and -mRNA, which did not exceed those of stretch, isoprenaline or phenylephrine alone. However, while CMS reduced the Cx43-protein/mRNA ratio, adrenergic stimulation increased Cx43-protein/mRNA ratio. While isoprenaline and phenylephrine increased Cx43-phosphorylation, additional CMS significantly reduced P-Cx43/Cx43 ratio. For further investigation of the underlying signal transduction pathway, we examined the phosphorylated forms of ERK1/2, GSK3β and AKT and could demonstrate that these protein kinases are also significantly up-regulated following stretch or adrenoceptor stimulation. Again the combined treatment of cardiomyocytes with CMS and isoprenaline or phenylephrine had no additive effects. Thus, the combination of α- or β-adrenoceptor stimulation and CMS up-regulates Cx43 expression and leads to phosphorylation of ERK1/2 and AKT (=activation) and of GSK3β (=inactivation). There were no significant additive effects compared to CMS or adrenergic stimulation alone indicating a possible ceiling effect. However, CMS and adrenergic stimulation differentially affected Cx43-protein/mRNA ratio and Cx43-phosphorylation. [Copyright &y& Elsevier]

Abstract: It has been reported that stress-related activation of the noradrenergic system strengthens the formation of aversive memories and that beta-adrenergic receptors seem to be involved in this emotional memory processing. In this study, the effects of beta-adrenergic compounds on the extinction of contextual conditioned fear responses were evaluated. Rats were trained with footshock in a conditioning box. In the 3days following the training, the animals were re-exposed to the apparatus and received either a single or repeated intraperitoneal injections of the beta-adrenergic antagonist propranolol, the beta-adrenergic agonist isoproterenol, or saline 30min before (acquisition of extinction) or immediately after (consolidation of extinction) the extinction sessions. A drug-free session was performed on the last day. While repeated isoproterenol treatment facilitated the consolidation of contextual fear extinction, repeated propranolol administration impaired the acquisition and the consolidation of this process. Further, the role of ventromedial prefrontal cortex (vmPFC) in the extinction of contextual conditioned fear was tested with an immunohistochemistry assay. Our results show a reduction in Fos-protein expression between the first and the last extinction session. In a follow-up experiment, intra-vmPFC microinjection of isoproterenol before the first extinction session facilitated the extinction of contextual fear. This facilitation was antagonized by pre-treatment with atenolol, suggesting that this change is mediated by beta-1-adrenergic activity. Our results reinforce the role of the vmPFC in fear extinction mechanisms, suggesting that vmPFC-beta-1-adrenergic receptor activation underlies part of the facilitation of the fear extinction processes. [ABSTRACT FROM AUTHOR]

Abstract: Membrane rafts and caveolae are specialized microdomains of the cell membrane that form physical platforms for compartmentalization of signalling molecules. Here, we intended to gain insight into the consequences of caveolar localization in G protein-coupled receptor function. We analysed β2-adrenoceptor signalling in purified CRLDF (caveolin-rich low density fractions) of β2-adrenoceptor-overexpressing HEK-293 cells. β2-adrenoceptor and Gs immunoreactivities and forskolin-stimulated adenylate cyclase activity were all detected in CRLDF obtained by the conventional raft purification method that uses Triton X-100 solubilization. However, Triton X-100 caused a complete loss of the functional coupling between β2-adrenoceptor, Gs and adenylate cyclase. Therefore, we developed an optimized purification method based on n-octyl-β-d-glucopyranoside solubilization, where the functional properties of β2-adrenoceptor, Gs and adenylate cyclase were preserved in the CRLDF. Using this method, we showed that isoproterenol-stimulated adenylate cyclase activity was similar in CRLDF and bulk membrane preparations of HEK-293 cells that overexpress β2-adrenoceptor or β2-adrenoceptor–Gs fusion. Accordingly, treatment of cells with methyl-β-cyclodextrin, a caveola-disrupting agent, did not affect β2-adrenoceptor-induced cAMP response. Likewise, these responses were insensitive to caveolin 1 and 2 overexpression. On the other hand, methyl-β-cyclodextrin treatment did decrease β2-adrenoceptor-induced ERK phosphorylation. However, the latter effect of methyl-β-cyclodextrin could be attributed to a non-specific effect rather than its ability to disrupt membrane microdomains. We showed that localization in the raft microdomains did not affect the signalling efficiency of β2-adrenoceptor–Gs–adenylate cyclase pathway, and that methyl-β-cyclodextrin may inhibit signalling by directly affecting the signalling system independently of its caveola-disrupting property. [Copyright &y& Elsevier]

Abstract: Memory consolidation is enhanced by emotional arousal, an effect mediated by noradrenergic beta-receptor signaling. Norepinephrine strengthens consolidation of both appetitive and aversive learning, and is implicated in extinction of conditioned responses. In this review, we summarize work on the noradrenergic mechanisms of extinction learning and implications for extinction-based exposure therapy. The evidence suggests that norepinephrine release evoked by conditioned stimuli during extinction strengthens extinction memory via beta-receptor signaling. The modulatory effect of norepinephrine during extinction depends on predictable presentation of conditioned stimuli and optimal levels of norepinephrine release. Mechanistically, norepinephrine acts to increase cellular excitability and enhance synaptic plasticity within extinction-related neural circuitry. Currently, drugs that modulate norepinephrine are being used to treat symptoms of anxiety disorders, and are now being tested as pharmacotherapeutic prophalactics in the prevention of chronic posttraumatic stress reactions and as adjuncts to extinction-based exposure therapy. Studies of these new applications of noradrenergic drugs show a converging pattern of results with basic science suggesting ways in which basic laboratory findings can be translated into procedures to enhance clinical outcomes. [Copyright &y& Elsevier]

The adrenergic receptors mediate a wide variety of physiological responses, including vasodilatation and vasoconstriction, heart rate modulation, and others. Beta-adrenergic antagonists ('beta-blockers') thus constitute a widely used class of drugs in cardiovascular medicine as well as in management of anxiety, migraine, and glaucoma. The importance of the hydrophobic effect has been evidenced for a wide range of beta-blocker properties. To better understand the role of the hydrophobic effect in recognition of beta-blockers by their receptor, we carried out a molecular docking study combined with an original approach to estimate receptor-ligand hydrophobic interactions. The proposed method is based on automatic detection of molecular fragments in ligands and the analysis of their interactions with receptors separately. A series of beta-blockers, based on phenylethanolamines and phenoxypropanolamines, were docked to the beta2-adrenoceptor binding site in the crystal structure. Hydrophobic complementarity between the ligand and the receptor was calculated using the PLATINUM web-server (http://model.nmr.ru/platinum). Based on the analysis of the hydrophobic match for molecular fragments of beta-blockers, we have developed a new scoring function which efficiently predicts dissociation constant (pKd) with strong correlations (r2∼ 0.8) with experimental data. [ABSTRACT FROM AUTHOR]

Abstract: The β-adrenergic signaling pathway represents a novel therapeutic target for skeletal muscle wasting and weakness due to its role in the mechanisms controlling protein synthesis and degradation and in modulating fiber type. Stimulation of the pathway with β-adrenoceptor agonists (β-agonists) has therapeutic potential for muscle wasting disorders including: sarcopenia, cancer cachexia, disuse and inactivity, unloading or microgravity, sepsis and other metabolic disorders, denervation, burns, HIV-AIDS, chronic kidney or heart failure, and neuromuscular diseases. However, there are also pitfalls associated with β-agonist administration and clinical applications have so far been limited, largely because of cardiovascular side effects. In rats and mice, newer generation β-agonists (such as formoterol) can elicit an anabolic response in skeletal muscle even at very low doses, with reduced effects on the heart and cardiovascular system compared with older generation β-agonists (such as fenoterol and clenbuterol). However, the potentially deleterious cardiovascular side effects of β-agonists have not been obviated completely and so it is important to refine their development and therapeutic approach in order to overcome these obstacles. This review describes the therapeutic potential of stimulating the β-adrenergic signaling pathway with β-agonists, highlighting the beneficial effects on skeletal muscle structure and function and identifying some of the pitfalls associated with short- and long-term β-agonist administration. The review also identifies some important, but as yet unanswered questions, regarding the importance of β-adrenoceptor signaling in muscle health and disease and the strategies needed to improve the efficacy and safety of β-agonists for muscle wasting disorders. [Copyright &y& Elsevier]

Abstract: Transcripts for the PDE4A10 cyclic AMP phosphodiesterase isoform are present in a wide variety of rat tissues including the heart. Sequence comparisons between the putative human and mouse promoters revealed a number of conserved regions including both an Sp1 and a CREB-binding site. The putative mouse PDE4A10 promoter was amplified from genomic DNA and sub-cloned into a luciferase reporter vector for investigation of activity in neonatal cardiac myocytes. Transfection with this construct identified a high level of luciferase expression in neonatal cardiac myocytes. Surprisingly, this activity was down-regulated by elevation of intracellular cAMP through a process involving PKA, but not EPAC, signalling. Such inhibition of the rodent PDE4A10 promoter activity in response to elevated cAMP levels is in contrast to the PDE4 promoters so far described. Site-directed mutagenesis revealed that the Sp1 binding site at promoter position −348 to −336 is responsible for the basal constitutive expression of murine PDE4A10. The conserved CREB-binding motif at position −370 to −363 also contributes to basal promoter activity but does not in itself confer cAMP inhibition upon the PDE4A10 promoter. EMSA analysis confirmed the authenticity of CREB and Sp1 binding sites. The transcriptional start site was identified to be an adenine residue at position −55 in the mouse PDE4A10 promoter. We present evidence that this novel down-regulation of PDE4A10 is mediated by the transcription factor ICER in a PKA dependent manner. The pool of cAMP in cardiac myocytes that down-regulates PDE4A10 is regulated by β-adrenoceptor coupled adenylyl cyclase activity and via hydrolysis determined predominantly by the action of PDE4 (cAMP phosphodiesterase-4) and not PDE3 (cAMP phosphodiesterase-3). We suggest that increased cAMP may remodel cAMP-mediated signalling events by not only increasing the expression of specific PDE4 cAMP phosphodiesterases but also by down-regulating specific isoforms, such as is shown here for PDE4A10 in cardiac myocytes. [Copyright &y& Elsevier]

Abstract: Introduction: The aim was to establish a robust, 96-well, cell-based assay to assess the potency and persistence of action of agonists acting at human recombinant β2 adrenoceptors expressed in CHO (Chinese Hamster Ovary) cells and to compare this with published duration of action data in guinea pig isolated trachea and human bronchus. Methods: Cells were treated with either: (i) β-adrenoceptor agonist for 30 min, washed and cyclicAMP (cAMP) measured 30 min later—termed ‘washed’ cells or, (ii) treated with solvent for 30 min, washed, and then treated with β-adrenoceptor agonist for 30 min and cAMP measured—termed ‘unwashed’ cells. The ‘washed’ EC50 was divided by the ‘unwashed’ EC50 to determine a rightward shift concentration ratio, which was indicative of the persistence of action at the receptor. Results: At the β2 adrenoceptor salmeterol, carmoterol and indacaterol were resistant to washing with a concentration ratio of <5, indicating a long persistence of action, whereas formoterol, isoprenaline and salbutamol were washed out with a ratio of 32, >294 and >800 respectively, suggesting a shorter persistence of action. At β1 and β3 adrenoceptors all compounds washed out. The persistent effects of salmeterol at β2 following washing could be reversed by the selective β2 antagonist ICI 118551, suggesting continued receptor activation. Discussion: The data presented agree well with published data assessing duration of action of β2 agonists in human isolated bronchus and guinea pig isolated trachea. Key features are: (a) it is a 96-well format which can be used to assess many compounds in a single experiment, (b) both potency and persistence of agonist action are assessed in the same assay, (c) any effects of concentration on the persistence of action can be highlighted, and (d) it allows triage of compounds prior to tissue bath studies thus reducing the use of animal tissue. [Copyright &y& Elsevier]

Diabetic patients have a decreased incidence of acute respiratory distress syndrome, but the mechanism responsible for the decreased incidence is uncertain. Reabsorption of alveolar edema fluid (alveolar fluid clearance) has been considered to play an important role in resolution of acute respiratory distress syndrome. However, little is known regarding alveolar fluid clearance in diabetes mellitus. Since the obese Zucker rat has been used as an experimental model for diabetes mellitus, we determined if alveolar fluid clearance increased in the obese Zucker rat. First, we compared alveolar fluid clearance in obese Zucker rats with that in lean Zucker rats and Sprague-Dawley (SD) rats. Then, we determined the role of sodium channel, Na,K-ATPase, and β2-adrenoceptor, which drives alveolar fluid clearance, in obese Zucker rats. Alveolar fluid clearance was estimated by the progressive increase in alveolar albumin concentrations in the isolated lungs. We found that basal alveolar fluid clearance in obese Zucker rats was two-fold greater than that in lean Zucker rats and SD rats. The mRNA expression of α1-, β1-Na, K-ATPase and β2-adrenoceptor, but not mRNA expression of sodium channel, increased in obese Zucker rats. A selective β2-agrenergic antagonist, but not a Na, K-ATPase inhibitor, specifically inhibited the increase in alveolar fluid clearance in obese Zucker rats. These results indicate that overexpression of β2-adrenoceptor primarily increases basal alveolar fluid clearance in the obese Zucker rat. We speculate that the stimulation of alveolar fluid clearance ameliorates acute respiratory distress syndrome in patients with diabetes mellitus. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, the interaction between morphine and the beta-adrenergic receptor antagonist, propranolol (PROP), in memory consolidation was investigated in a two-trial recognition Y-maze task. Four sets of Y-maze experiments were carried out in mice, with 2 and 4 h inter-trial intervals (ITI) and all drugs administered immediately after the training trials. In the first and second sets of experiments, post-training administration of morphine (0.25 and 2.5 mg/kg) or PROP (2, 10 and 20 mg/kg) alone did not impair memory consolidation after a 2 h ITI. However, in the third and fourth sets of experiments, co-administration of these ineffective doses of morphine (0.25 and 2.5 mg/kg) and PROP (2, 10 and 20 mg/kg) disrupted memory consolidation after a 2 h ITI. Moreover, the relatively higher dose of morphine (2.5 mg/kg) plus the relatively higher doses of PROP (10 and 20 mg/kg) disrupted memory consolidation to a greater extent after a 2 h ITI. Locomotor activity was not affected by any of the drug treatments. Our data shows that morphine and PROP co-administration disrupts the consolidation of spatial recognition memory, suggesting that inactivation of the beta-adrenergic system may contribute to morphine-induced impairment of memory. [Copyright &y& Elsevier]

Abstract: The effects of noradrenaline (NA) on the inhibitory responses to GABA were studied in vivo in neurons of the vestibular nuclei of the rat using extracellular recordings of single unit electrical activity and a microiontophoretic technique of drug application in loco. NA application influenced GABA-evoked inhibitions in 82% of tested neurons, depressing them in 42% and enhancing them in 40% of cases. The more frequent action of NA on GABA responses was depressive in lateral and superior vestibular nuclei (50% of neurons) and enhancing in the remaining nuclei (56% of neurons). The most intense effect of NA application was the enhancement of GABA responses induced in a population of lateral vestibular nucleus neurons, characterized by a background firing rate significantly higher than that of other units. The alpha2 noradrenergic receptor agonist clonidine mimicked the enhancing action of NA on GABA responses; this action was blocked by application of the specific alpha2 antagonist yohimbine. The beta adrenergic agonist isoproterenol induced either depressive or enhancing effects on GABA responses; the former more than the latter were totally or partially blocked by application of the beta antagonist timolol. It is concluded that NA enhances GABA responses by acting on noradrenergic alpha2 and to a lesser extent beta receptors, whereas depressive action involves beta receptors only. These results confirm the hypothesis that the noradrenergic system participates in the regulation of the vestibulospinal and the vestibulo-ocular reflexes and suggest that conspicuous changes of NA content in brain due to aging or stress could lead to a deterioration in the mechanisms of normal vestibular function. [Copyright &y& Elsevier]

Abstract: Small molecules interacting with aminergic G-protein coupled receptors represent a number of very successful drugs. G-protein coupled receptors continue to be a significant group of targets for pharmaceutical intervention, and modifying their activity through small molecules is a major focus of drug development. Previously, these small molecules could be easily fit in models, as agonists, partial agonists or antagonists. More recently, however, these lines have been blurred as it is increasingly recognized that ligands can interact with receptors in various ways. Analysis of beta-adrenoceptors has revealed that several sites or states exist for the individual receptors. The putative atypical β4-adrenoceptor identified on heart and adipose tissue is now recognized as a unique β1-adrenoceptor state. Similarly, a unique β3-adrenoceptor state has been identified using the aryloxypropanolamine CGP-12,177 and cloned receptor systems. Here we expand upon these observations, by describing an atypical state of the β3-adrenoceptor that exists endogenously in adipose tissue. Furthermore, we describe novel arylethanolamine ligands that interact with this atypical state of the β3-adrenoceptor with high affinity and provide additional tools to investigate the atypical β3-adrenoceptor state to determine whether it can be influenced for therapeutic purposes. [Copyright &y& Elsevier]

Abstract: The present experiments were designed to study fear conditioning as an emotional learning task with disrupted visceral feedback. For that purpose we used the peripherally acting β1-adrenoceptor blocker atenolol and studied its effects on the behavior of male C57BL/6JOlaHsd mice in an exploration-related test and during fear-conditioning. In the first experiment, we treated mice with saline or different doses of the β1-adrenergic blocker atenolol (5mg/kg and 20mg/kg body weight i.p.) 30min before behavioral testing in a motility box. Only the high but not the low dose of atenolol led to a reduction of locomotor activity (p <0.02). Factors known to be related to emotionality (rearing, area preference) were unaffected. In a second experiment, saline- and atenolol-treated mice (same dosages and mode of application) were trained for auditory fear conditioning, and 24h later they were retested in the same environment. We found differences between the effects of atenolol upon contextual- and cue-fear conditioning. Animals treated with 20mg/kg BW doses of atenolol showed significantly decreased background contextual fear compared to saline-treated control animals. In contrast, no differences were found during CS presentation in the conditioning context between atenolol-treated animals and saline-treated controls, independent from a paired or an unpaired conditioning paradigm. Thus, the blockade of peripheral β1-adrenoceptors by atenolol may have disrupted the positive feedback to the central nervous system via visceral afferents resulting in a decreased locomotor activity and background contextual fear. [Copyright &y& Elsevier]

Aims: The Dutch Hypothesis suggests that asthma and chronic obstructive pulmonary disease may share some pathogenic mechanisms. There is considerable evidence that polymorphisms of the β2 adrenoceptor have disease-modifying roles in juvenile onset asthma, determining severity and response to β agonists, but not determining disease susceptibility. There is evidence from family and twin studies to suggest that chronic obstructive pulmonary disease (COPD) also has a significant genetic component. We therefore hypothesized that β2 adrenoceptor polymorphisms would have similar disease modifying roles in patients with COPD. Methods: One hundred and ninety-five COPD subjects and 142 matched controls were recruited. All had detailed clinical phenotyping. Subjects were genotyped for the Agr → Gly polymorphism at codon 16, the Gln → Glu polymorphism at codon 27, and the SNPC/T-47 promoter polymorphism. Results: In patients with COPD (mean age 67, 57% male), individuals with the homozygous Gly16/homozygous Glu27/homozygous SNP −47*C genotype had significantly worse lung function as measured by forced expiratory volume 1, expressed as a percentage of its predicted value (39.2 compared with 45.8, P = 0.004), and for forced vital capacity (FVC) percent predicted (77.2 compared with 70.4, P = 0.02). The polymorphisms had no effect on disease susceptibility. Conclusion: The Arg16, Gln27, SNPC/T-47 β2 adrenoceptor polymorphisms may have disease modifying roles in patients with COPD. [ABSTRACT FROM AUTHOR]

Aim: Relaxant effects of different β-adrenoceptor agonists on porcine and human detrusor were examined. Thus, the β-adrenoceptor subtype mainly responsible for relaxation in the detrusor muscle of pigs was characterized. Additionally, different effects of several β-agonists in both species were shown. Methods: Experiments were performed on muscle strips of porcine and human detrusor suspended in a tissue bath. The relaxant effects of the non-selective β-agonist isoprenaline, the selective β2-agonists procaterol, salbutamol and the selective β3-agonists BRL 37344, CL 316 243 and CGP 12177 on potassium-induced contraction were investigated. The inhibitory effect of different substances on the maximum contraction and the rank order of potency for endogenous catecholamines was determined in pigs. Furthermore, concentration-relaxation curves were performed for pigs and humans. Results: Pigs: In the pre-treatment experiments isoprenaline and procaterol showed similar effects. The concentration–response experiments showed that the maximum relaxation induced by procaterol and salbutamol was more than 90%, not significantly different from isoprenaline, whereas the maximum relaxations of CL 316 243, BRL 37344 and CGP 12177 amounted to 68, 70 or 30%, respectively. Rank order of potencies was isoprenaline ≥ adrenaline > noradrenaline. Humans: Isoprenaline, procaterol, salbutamol and CL 316 243 showed a maximum relaxation of 80, 41, 24 and 35% and pD2 values of 6.24, 5.65, 5.48 and 5.55, respectively. Conclusion: β2-receptors play a main functional role in mediating relaxation of porcine detrusor. Selective β2- and β3-agonists similarly relax the human detrusor. Effects were smaller compared with the pig. [ABSTRACT FROM AUTHOR]

Abstract: Low-affinity state beta1-adrenoceptor (β1-AR) was functionally expressed in some blood vessels and was different from β1, β2 and β3-AR. In rat aorta, low-affinity state β1-AR activation produced an endothelium-independent relaxation which was impaired in spontaneously hypertensive rats (SHRs). In the present work, we investigated whether renin–angiotensin system was involved in this alteration by evaluating the effects of enalapril, an angiotensin converting enzyme (ACE) inhibitor or losartan, an AT1 angiotensin receptor antagonist. Cumulative concentration–response curves to low-affinity state β1-AR agonists (CGP 12177, cyanopindolol or alprenolol) and to NS 1619, a large conductance Ca2+-activated K+ channels (BK) agonist were performed in denuded aortic rings isolated from control or treated Wistar Kyoto (WKY) rats or SHRs in different experimental conditions. The low-affinity state β1-AR-mediated aortic vasodilation was impaired in 5 and 12 weeks old SHRs when compared to age-matched WKY. Twelve days enalapril (5mg/kg/day) or losartan (15mg/kg/day) treatments reduced systolic blood pressure (SBP) only in 12 weeks old SHRs whereas no significant change was observed in other groups. These treatments improved low-affinity state β1-AR effect only in SHRs groups. In 12 weeks old WKY rats, CGP 12177-induced relaxation was insensitive to glibenclamide, a channel blocker, but was reduced by TEA or iberiotoxin, two large conductance Ca2+-activated K+ channel (BK) blockers. The impairment of NS 1619-induced vasodilation in both 5 and 12 weeks old SHRs was restored by enalapril or losartan. These results suggested that improvement of the low-affinity state β1-AR-mediated vasodilation in 5 and 12 weeks old SHRs could be attributed to enhanced BK channels-induced hyperpolarization in SHRs independently of lowering of SBP. [Copyright &y& Elsevier]

The ventral medial prefrontal cortex (vMPFC) is involved in central cardiovascular control. In the present study, we studied the cardiovascular effects of injections ofl-glutamate into the vMPFC of unanaesthetized rats and the mechanisms of these effects. Male Wistar rats were used andl-glutamate was microinjected in the vMPFC in a final volume of 200 nL. Microinjections ofl-glutamate (9, 27, 81, 150 or 300 nmol) caused long-lasting, dose-related pressor and tachycardic responses in unanaesthetized rats. No differences were observed among cardiovascular responses whenl-glutamate was injected into the three sub-areas that comprise the vMPFC, namely the prelimbic, the infralimbic and the dorsal peduncular cortices. No responses were observed when the dose of 81 nmol ofl-glutamate was microinjected into surrounding structures such as the cingulate cortex area 1, the corpus callosum and the tenia tecta, indicating a predominant action on the vMPFC. The cardiovascular response tol-glutamate into the vMPFC was blocked by intravenous pretreatment with the ganglion blocker pentolinium (10 mg/kg, i.v.) or the beta1-adrenoceptor antagonist atenolol (1.5 mg/kg, i.v.), supporting the involvement of the cardiac sympathetic nervous system in the response tol-glutamate. Pretreatment with the muscarinic antagonist homatropine methyl bromide (1 mg/kg, i.v.) reduced the latency to the onset of the pressor and tachycardic responses tol-glutamate injected into the vMPFC without significant effects on response duration or maximum effect. We conclude that stimulation of the vMPFC withl-glutamate caused pressor and tachycardic responses in unanaesthetized rats, responses which were dependent on cardiac sympathetic nerve activation and were potentiated by blockade of peripheral muscarinic receptors. [ABSTRACT FROM AUTHOR]

: ObjectivesTo investigate whether myocardial beta-adrenoceptor (beta-AR) downregulation precedes and predicts left ventricular (LV) dilation after acute myocardial infarction (AMI), we measured beta-AR density within four weeks of AMI and correlated it with serial measurements of LV volumes.: BackgroundPatients who develop heart failure following AMI have an increased sympathetic drive to the heart within the first four weeks after infarction.: MethodsWe prospectively studied 61 patients in whom AMI was the first presentation of coronary artery disease (CAD) and with no signs of heart failure. The LV volumes were measured one, three, and six months after AMI by echocardiography. Beta-AR density was measured using positron emission tomography with S-[11C]CGP 12177. Seventeen matched healthy volunteers served as controls.: ResultsWhole heart beta-AR density was lower in patients than in controls (6.25 ± 0.98 pmol/g vs. 8.32 ± 2.14 pmol/g, p < 0.0001). In patients, beta-AR density was inversely correlated with end-systolic and end-diastolic volumes six months after AMI. Patients whose LV was dilated at six months had a lower beta-AR density in noninfarcted myocardium than patients without dilation (6.15 pmol/g vs. 6.98 pmol/g, p = 0.008). In addition, beta-AR density in noninfarcted myocardium was higher when the infarct-related artery was patent (6.87 ± 1.14 pmol/g vs. 5.76 ± 0.86 pmol/g occluded, p < 0.01).: ConclusionsMyocardial beta-AR density is reduced after AMI in the absence of heart failure, and the reduction predicts later LV dilation. These data are suggestive of an enhanced sympathetic drive to the heart, having an important etiologic role in LV remodeling after AMI. [Copyright &y& Elsevier]