Adrenoceptor sub-type involvement in Ca2+ current stimulation by noradrenaline in human and rabbit atrial myocytes.

Atrial fibrillation (AF) from elevated adrenergic activity may involve increased atrial L-type Ca2+ current (ICaL) by noradrenaline (NA). However, the contribution of the adrenoceptor (AR) sub-types to such ICaL-increase is poorly understood, particularly in human. We therefore investigated effects of various broad-action and sub-type-specific α- and ß-AR antagonists on NA-stimulated atrial ICaL. ICaL was recorded by whole-cell-patch clamp at 37 °C in myocytes isolated enzymatically from atrial tissues from consenting patients undergoing elective cardiac surgery and from rabbits. NA markedly increased human atrial ICaL, maximally by ~ 2.5-fold, with EC75 310 nM. Propranolol (ß1 + ß2-AR antagonist, 0.2 microM) substantially decreased NA (310 nM)-stimulated ICaL, in human and rabbit. Phentolamine (α1 + α2-AR antagonist, 1 microM) also decreased NA-stimulated ICaL. CGP20712A (ß1-AR antagonist, 0.3 microM) and prazosin (α1-AR antagonist, 0.5 microM) each decreased NA-stimulated ICaL in both species. ICI118551 (ß2-AR antagonist, 0.1 microM), in the presence of NA + CGP20712A, had no significant effect on ICaL in human atrial myocytes, but increased it in rabbit. Yohimbine (α2-AR antagonist, 10 microM), with NA + prazosin, had no significant effect on human or rabbit ICaL. Stimulation of atrial ICaL by NA is mediated, based on AR sub-type antagonist responses, mainly by activating ß1- and α1-ARs in both human and rabbit, with a ß2-inhibitory contribution evident in rabbit, and negligible α2 involvement in either species. This improved understanding of AR sub-type contributions to noradrenergic activation of atrial ICaL could help inform future potential optimisation of pharmacological AR-antagonism strategies for inhibiting adrenergic AF.

Assessment of melatonin-alpha adrenergic receptor complexes by molecular docking analysis.

The pineal melatonin (N-acetyl-5-methoxytryptamine) is a molecule associated in a way or another with probably all physiological systems, aiming to fulfil its functional integrative roles in central nervous system activity, sleep and wakefulness cycles, energy metabolism and thermoregulation, immune, reproductive, endocrine, cardiovascular, respiratory and excretory systems. Within this context, the present study aimed to assess in silico the formation of complexes between ligand melatonin and other potential receptor proteins by molecular docking analyses. The main steps established in this experimental procedure were: a) search and selection of the 3D structure of the melatonin from DrugBank; b) search and selection of 3D structures of other target receptor proteins using STRING, protein BLAST and database PDB; and c) formation of the complexes between melatonin and receptors selected using AutoDock4.0 server by molecular docking analyses. High reliability score and significant similarity were only identified between type 1B melatonin and alpha-2A adrenergic receptor. Thus, molecular docking assays were carried out using ligand melatonin and crystallographic structures of the alpha-2A adrenergic receptor coupled to an antagonist (ID PDB 6kux) and a partial agonist (ID PDB 6kuy) available in the database PDB. Binding energy values of -6.79 and -6.98 kcal/mol and structural stability by non-covalent intermolecular interactions were predicted during the formation of complexes between melatonin and alpha-2A adrenergic receptor 6kux and 6kuy, respectively. In this way, the findings described in current study may indicate strong interactions between melatonin and adrenoceptors, suggesting its possible partial agonist effect on the activation of the alfa-2A adrenergic receptor.

Is the Pannexin-1 Channel a Mechanism Underlying Hypertension in Humans? a Translational Study of Human Hypertension.

BACKGROUND: In preclinical models, the pannexin-1 channel has been shown to be involved in blood pressure regulation through an effect on peripheral vascular resistance. Pannexin-1 releases ATP, which can activate constrictive purinergic receptors on the smooth muscle cells. Pannexin-1 opening is proposed to be mediated by α-adrenergic receptors to potentiate sympathetic constriction. This positions pannexin-1 as a putative pharmacological target in blood pressure regulation in humans. The aim was to provide the first translational evidence for a role of pannexin-1 in essential hypertension in humans by use of an advanced invasive mechanistic approach. METHODS: Middle-aged stage-1 hypertensive (n=13; 135.7±6.4 over 83.7±3.7 mm Hg) and normotensive men (n=12; 117.3±5.7 over 72.2±3.5 mm Hg) were included. Blood pressure and leg vascular resistance were determined during femoral arterial infusion of tyramine (α-adrenergic receptor stimulation), sodium nitroprusside, and acetylcholine. Measurements were made during control conditions and with pannexin-1 blockade (3000 mg probenecid). Expression of Pannexin-1, purinergic- and α-adrenergic receptors in skeletal muscle biopsies was determined by Western blot. RESULTS: The changes in leg vascular resistance in response to tyramine (+289% versus +222%), sodium nitroprusside (-82% versus -78%) and acetylcholine (-40% versus -44%) infusion were not different between the 2 groups (P>0.05) and pannexin-1 blockade did not alter these variables (P>0.05). Expression of pannexin-1 and of purinergic- and α-adrenergic receptors was not different between the 2 groups (P>0.05). CONCLUSIONS: Contrary to our hypothesis, the data demonstrate that pannexin-1 does not contribute to the elevated blood pressure in essential hypertension, a finding, which also opposes that reported in preclinical models.

Alpha and beta adrenergic receptors modulate keratinocyte migration.

Keratinocyte migration into skin wounds is the step of the healing process that correlates with the wound closure rate. Keratinocyte migration, and wound epithelialization are decreased when beta 2-adrenergic receptors (B2AR) are activated by 1 µM epinephrine/adrenaline, resulting in delayed wound healing in human and mouse skin. In the present study, we found paradoxically, that in a subset of keratinocyte strains exposure to low concentrations of epinephrine (0.1 nM) increased, rather than decreased, their migratory rate. We find that both the alpha- and the beta-adrenergic receptors are expressed in human keratinocytes, and expression of alpha-2 AR subtypes demonstrated for the first time. Therefore, we tested if the alpha-AR could be modulating the increased migratory response observed in these cell strains. By using specific inhibitors to alpha-AR, we demonstrated that blocking A2B-AR could reverse the rapid cell migration induced by the 0.1 nM epinephrine. Phosphorylation of ERK was elevated after 1-10 minutes of the low epinephrine treatment and the A2B-AR inhibitor blocked the ERK phosphorylation. The results suggest that both the A2B-AR and B2AR mediate keratinocyte migration, in which with a low level of epinephrine treatment, A2B-AR could alter the B2AR signals and regulate the migration rate.

Opposing functions of α- and ß-adrenoceptors in the formation of processes by cultured astrocytes.

Astrocytes are glial cells with numerous fine processes which are important for the functions of the central nervous system. The activation of ß-adrenoceptors induces process formation of astrocytes via cyclic AMP (cAMP) signaling. However, the role of α-adrenoceptors in the astrocyte morphology has not been elucidated. Here, we examined it by using cultured astrocytes from neonatal rat spinal cords and cortices. Exposure of these cells to noradrenaline and the ß-adrenoceptor agonist isoproterenol increased intracellular cAMP levels and induced the formation of processes. Noradrenaline-induced process formation was enhanced with the α1-adrenoceptor antagonist prazosin and α2-adrenoceptor antagonist atipamezole. Atipamezole also enhanced noradrenaline-induced cAMP elevation. Isoproterenol-induced process formation was not inhibited by the α1-adrenoceptor agonist phenylephrine but was inhibited by the α2-adrenoceptor agonist dexmedetomidine. Dexmedetomidine also inhibited process formation induced by the adenylate cyclase activator forskolin and the membrane-permeable cAMP analog dibutyryl-cAMP. Moreover, dexmedetomidine inhibited cAMP-independent process formation induced by adenosine or the Rho-associated kinase inhibitor Y27632. In the presence of propranolol, noradrenaline inhibited Y27632-induced process formation, which was abolished by prazosin or atipamezole. These results demonstrate that α-adrenoceptors inhibit both cAMP-dependent and -independent astrocytic process formation.

Catecholamines Induce Endoplasmic Reticulum Stress Via Both Alpha and Beta Receptors.

Severely burned patients suffer from a hypermetabolic syndrome that can last for years after the injury has resolved. The underlying cause of these metabolic alterations most likely involves the persistent elevated catecholamine levels that follow the surge induced by thermal injury. At the cellular level, endoplasmic reticulum (ER) stress in metabolic tissues is a hallmark observed in patients following burn injury and is associated with several detrimental effects. Therefore, ER stress could be the underlying cellular mechanism of persistent hypermetabolism in burned patients. Here, we show that catecholamines induce ER stress and that adreno-receptor blockers reduce stress responses in the HepG2 hepatocyte cell line. Our results also indicate that norepinephrine (NE) significantly induces ER stress in HepG2 cells and 3T3L1 mouse adipocytes. Furthermore, we demonstrate that the alpha-1 blocker, prazosin, and beta blocker, propranolol, block ER stress induced by NE. We also show that the effects of catecholamines in inducing ER stress are cell type-specific, as NE treatment failed to evoke ER stress in human fibroblasts. Thus, these findings reveal the mechanisms used by catecholamines to alter metabolism and suggest inhibition of the receptors utilized by these agents should be further explored as a potential target for the treatment of ER stress-mediated disease.

Diverse Effects of Noradrenaline and Adrenaline on the Quantal Secretion of Acetylcholine at the Mouse Neuromuscular Junction.

Despite the long history of investigations of adrenergic compounds and their biological effects, specific mechanisms of their action in distinct compartments of the motor unit remain obscure. Recent results have suggested that not only skeletal muscles but also the neuromuscular junctions represent important targets for the action of catecholamines. In this paper, we describe the effects of adrenaline and noradrenaline on the frequency of miniature endplate potentials, the quantal content of the evoked endplate potentials and the kinetics of acetylcholine quantal release in the motor nerve endings of the mouse diaphragm. Noradrenaline and adrenaline decreased the frequency of the spontaneous release of acetylcholine quanta. The effect of noradrenaline was prevented by the ß adrenoreceptor blocker propranolol, whereas the action of adrenaline was abolished by the α adrenoreceptor antagonist phentolamine. Noradrenaline did not alter the quantal content of endplate potentials, while adrenaline suppressed the evoked release of acetylcholine. Blocking the α adrenoreceptors prevented the decrease in quantal secretion caused by adrenaline. Quantal release became more asynchronous under noradrenaline, as evidenced by a greater dispersion of real synaptic delays; in contrast, adrenaline synchronized the release process. Our data suggest an involvement of α and ß adrenoreceptors in the diverse modulation of the frequency of miniature endplate potentials, the quantal content of the evoked endplate potentials and the kinetics of acetylcholine quantal secretion in the mouse neuromuscular junction. Moreover, the adrenoblockers affected both the evoked and spontaneous quantal release of acetylcholine, suggesting the presence of endogenous catecholamines in the vicinity of cholinergic synapses.

The alpha- and beta-noradrenergic receptors blockade in the dorsal raphe nucleus impairs the panic-like response elaborated by medial hypothalamus neurons.

Dorsal raphe nucleus (DRN) neurons are reciprocally connected to the locus coeruleus (LC) and send neural pathways to the medial hypothalamus (MH). The aim of this work was to investigate whether the blockade of α1-, α2- or ß-noradrenergic receptors in the DRN or the inactivation of noradrenergic neurons in the LC modify defensive behaviours organised by MH neurons. For this purpose, Wistar male rats received microinjections of WB4101, RX821002, propranolol (α1-, α2- and ß-noradrenergic receptor antagonists, respectively) or physiological saline in the DRN, followed 10 min later by MH GABAA receptor blockade. Other groups of animals received DSP-4 (a noradrenergic neurotoxin), physiological saline or only a needle insertion (sham group) into the LC, and 5 days later, bicuculline or physiological saline was administered in the MH. In all these cases, after MH treatment, the frequency and duration of defensive responses were recorded over 15 min. An anterograde neural tract tracer was also deposited in the DRN. DRN neurons send pathways to lateral and dorsomedial hypothalamus. Blockade of α1- and ß-noradrenergic receptors in the DRN decreased escape reactions elicited by bicuculline microinjections in the MH. In addition, a significant increase in anxiety-like behaviours was observed after the blockade of α2-noradrenergic receptors in the DRN. LC pretreatment with DSP-4 decreased both anxiety- and panic attack-like behaviours evoked by GABAA receptor blockade in the MH. In summary, the present findings suggest that the norepinephrine-mediated system modulates defensive reactions organised by MH neurons at least in part via noradrenergic receptors recruitment on DRN neurons.

Participation of hepatic α/ß-adrenoceptors and AT1 receptors in glucose release and portal hypertensive response induced by adrenaline or angiotensin II.

It has been previously demonstrated that the hemodynamic effect induced by angiotensin II (AII) in the liver was completely abolished by losartan while glucose release was partially affected by losartan. Angiotensin II type 1 (AT1) and adrenergic (∝1- and ß-) receptors (AR) belong to the G-proteins superfamily, which signaling promote glycogen breakdown and glucose release. Interactive relationship between AR and AT1-R was shown after blockade of these receptors with specific antagonists. The isolated perfused rat liver was used to study hemodynamic and metabolic responses induced by AII and adrenaline (Adr) in the presence of AT1 (losartan) and ∝1-AR and ß-AR antagonists (prazosin and propranolol). All antagonists diminished the hemodynamic response induced by Adr. Losartan abolished hemodynamic response induced by AII, and AR antagonists had no effect when used alone. When combined, the antagonists caused a decrease in the hemodynamic response. The metabolic response induced by Adr was mainly mediated by ∝1-AR. A significant decrease in the hemodynamic response induced by Adr caused by losartan confirmed the participation of AT1-R. The metabolic response induced by AII was impaired by propranolol, indicating the participation of ß-AR. When both ARs were blocked, the hemodynamic and metabolic responses were impaired in a cumulative effect. These results suggested that both ARs might be responsible for AII effects. This possible cross-talk between ß-AR and AT1-R signaling in the hepatocytes has yet to be investigated and should be considered in the design of specific drugs.

No Protective Effect of Constitutive Activation of AMPK in Endothelial Cells on Vascular Function in Aged Obese Mice but Augmented α1-Adrenergic Contractions in Renal Arteries Reversible by Weight Loss.

BACKGROUND: Aging, obesity, and diabetes favor vascular dysfunction. Endothelial activation of adenosine monophosphate-activated protein kinase (AMPK) has protective effects in diabetes. METHODS: Mice with constitutive endothelial activation of AMPK (CA-AMPK) were given a high fat diet to induce obesity or kept on standard chow as lean controls for up to 2 years. A subset of obese animals was changed to standard chow after 30 weeks of high fat feeding. En-dothelium-dependent and endothelium-independent responses were examined by isometric tension recording. RESULTS AND CONCLUSION: Endothelium-dependent nitric oxide (NO)- and apamin plus charybdotoxin-sensitive relaxations were preserved and similar between aortic or renal arterial preparations of lean and obese CA-AMPK mice and their wild-type littermates. Despite comparable release of vasoconstrictor prostanoids, cyclooxygenase-dependent contractions were enhanced during NO synthase inhibition in carotid arterial rings of obese CA-AMPK mice. Contractions to the α1-adrenoceptor agonist phenylephrine were augmented in renal arteries of obese animals, a genotype-independent phenomenon reversible by weight loss. These data indicate a higher α1-adrenergic reactivity in renal arteries of aged mice with obesity. The current results highlight the potential of weight loss to alleviate vascular dysfunction. However, endothelial activation of the AMPK pathway in obesity may not be sufficient to prevent vascular dysfunction without lifestyle changes.

Participation of hepatic α/β-adrenoceptors and AT1 receptors in glucose release and portal hypertensive response induced by adrenaline or angiotensin II

It has been previously demonstrated that the hemodynamic effect induced by angiotensin II (AII) in the liver was completely abolished by losartan while glucose release was partially affected by losartan. Angiotensin II type 1 (AT1) and adrenergic (∝1- and β-) receptors (AR) belong to the G-proteins superfamily, which signaling promote glycogen breakdown and glucose release. Interactive relationship between AR and AT1-R was shown after blockade of these receptors with specific antagonists. The isolated perfused rat liver was used to study hemodynamic and metabolic responses induced by AII and adrenaline (Adr) in the presence of AT1 (losartan) and ∝1-AR and β-AR antagonists (prazosin and propranolol). All antagonists diminished the hemodynamic response induced by Adr. Losartan abolished hemodynamic response induced by AII, and AR antagonists had no effect when used alone. When combined, the antagonists caused a decrease in the hemodynamic response. The metabolic response induced by Adr was mainly mediated by ∝1-AR. A significant decrease in the hemodynamic response induced by Adr caused by losartan confirmed the participation of AT1-R. The metabolic response induced by AII was impaired by propranolol, indicating the participation of β-AR. When both ARs were blocked, the hemodynamic and metabolic responses were impaired in a cumulative effect. These results suggested that both ARs might be responsible for AII effects. This possible cross-talk between β-AR and AT1-R signaling in the hepatocytes has yet to be investigated and should be considered in the design of specific drugs.

Pathological prolongation of action potential duration as a cause of the reduced alpha-adrenoceptor-mediated negative inotropy in streptozotocin-induced diabetic mice myocardium.

Effect of pathological prolongation of action potential duration on the α-adrenoceptor-mediated negative inotropy was studied in streptozotocin-induced diabetic mice myocardium. In streptozotocin-treated mouse ventricular myocardium, which had longer duration of action potential than that in control mice, the negative inotropic response induced by phenylephrine was smaller than that in control mice. 4-Aminopyridine prolonged the action potential duration and decreased the negative inotropy in control mice. Cromakalim shortened the action potential duration and increased the negative inotropy in streptozotocin-treated mice. These results suggest that the reduced α-adrenoceptor-mediated inotropy in the diabetic mouse myocardium is partly due to its prolonged action potential.

Involvement of alpha- and beta-adrenoceptors in the automaticity of the isolated guinea pig pulmonary vein myocardium.

We examined the involvement of adrenoceptors in the automaticity of the pulmonary vein myocardium, which probably plays a crucial role in the generation of atrial fibrillation. The automatic activity of the myocardium in guinea pig pulmonary vein tissue preparations were monitored by contractile force or membrane potential measurement. In quiescent preparations, application of noradrenaline induced an automatic activity. The firing frequency was reduced by prazosin or atenolol. Methoxamine induced an automatic activity of low frequency, which was accelerated by further application of isoproterenol. In preparations driven at a constant frequency, noradrenaline, in the presence of atenolol, caused a depolarizing shift of the resting membrane potential and an increase in the slope of the diastolic depolarization. In contrast, in the presence of prazosin, noradrenaline had no effect on the slope, but caused acceleration of the late repolarization and a hyperpolarizing shift of the maximum diastolic potential. At clinically relevant concentrations, carvedilol significantly inhibited the noradrenaline-induced activity but bisoprolol did not. It was concluded that α1- and ß1-adrenoceptor stimulation enhance automaticity through different mechanisms in the guinea pig pulmonary vein myocardium. Dual blockade of these adrenoceptors appears to be effective for suppressing noradrenaline-induced pulmonary vein automaticity and probably atrial fibrillation.

Endothelium-dependent vasodilatory signalling modulates α1 -adrenergic vasoconstriction in contracting skeletal muscle of humans.

KEY POINTS: 'Functional sympatholysis' describes the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction, and is critical to ensure proper blood flow and oxygen delivery to metabolically active skeletal muscle. The signalling mechanism responsible for sympatholysis in healthy humans is unknown. Evidence from animal models has identified endothelium-derived hyperpolarization (EDH) as a potential mechanism capable of attenuating sympathetic vasoconstriction. In this study, increasing endothelium-dependent signalling during exercise significantly enhanced the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction in humans. This is the first study in humans to identify endothelium-dependent regulation of sympathetic vasoconstriction in contracting skeletal muscle, and specifically supports a role for EDH-like vasodilatory signalling. Impaired functional sympatholysis is a common feature of cardiovascular ageing, hypertension and heart failure, and thus identifying fundamental mechanisms responsible for sympatholysis is clinically relevant. ABSTRACT: Stimulation of α-adrenoceptors elicits vasoconstriction in resting skeletal muscle that is blunted during exercise in an intensity-dependent manner. In humans, the underlying mechanisms remain unclear. We tested the hypothesis that stimulating endothelium-dependent vasodilatory signalling will enhance the ability of contracting skeletal muscle to blunt α1 -adrenergic vasoconstriction. Changes in forearm vascular conductance (FVC; Doppler ultrasound, brachial intra-arterial pressure via catheter) to local intra-arterial infusion of phenylephrine (PE; α1 -adrenoceptor agonist) were calculated during (1) infusion of the endothelium-dependent vasodilators acetylcholine (ACh) and adenosine triphosphate (ATP), the endothelium-independent vasodilator (sodium nitroprusside, SNP), or potassium chloride (KCl) at rest; (2) mild or moderate intensity handgrip exercise; and (3) combined mild exercise + ACh, ATP, SNP, or KCl infusions in healthy adults. Robust vasoconstriction to PE was observed during vasodilator infusion alone and mild exercise, and this was blunted during moderate intensity exercise (ΔFVC: -34 ± 4 and -34 ± 3 vs. -13 ± 2%, respectively, P < 0.05). Infusion of ACh or ATP during mild exercise significantly attenuated PE vasoconstriction similar to levels observed during moderate exercise (ACh: -3 ± 4; ATP: -18 ± 4%). In contrast, infusion of SNP or KCl during mild exercise did not attenuate PE-mediated vasoconstriction (-32 ± 5 and -46 ± 3%). To further study the role of endothelium-dependent hyperpolarization (EDH), ACh trials were repeated with combined nitric oxide synthase and cyclooxygenase inhibition. Here, PE-mediated vasoconstriction was blunted at rest (blockade: -20 ± 5 vs. CONTROL: -31 ± 3% vs.; P < 0.05) and remained blunted during exercise (blockade: -15 ± 5 vs. CONTROL: -14 ± 5%). We conclude that stimulation of EDH-like vasodilatation can blunt α1 -adrenergic vasoconstriction in contracting skeletal muscle of humans.

Mirabegron relaxes urethral smooth muscle by a dual mechanism involving ß3 -adrenoceptor activation and α1 -adrenoceptor blockade.

LINKED ARTICLE: This article is commented on by Michel, M. C., pp. 429-430 of this issue. To view this commentary visit http://dx.doi.org/10.1111/bph.13379. BACKGROUND AND PURPOSE: Mirabegron is the first ß3 -adrenoceptor agonist approved for treatment of overactive bladder syndrome. This study aimed to investigate the effects of ß3 -adrenoceptor agonist mirabegron in mouse urethra. The possibility that mirabegron also exerts α1 -adrenoceptor antagonism was also tested in rat smooth muscle preparations presenting α1A - (vas deferens and prostate), α1D - (aorta) and α1B -adrenoceptors (spleen). EXPERIMENTAL APPROACH: Functional assays were carried out in mouse and rat isolated tissues. Competition assays for the specific binding of [(3) H]prazosin to membrane preparations of HEK-293 cells expressing each of the human α1 -adrenoceptors, as well as ß-adrenoceptor mRNA expression and cyclic AMP measurements in mouse urethra, were performed. KEY RESULTS: Mirabegron produced concentration-dependent urethral relaxations that were shifted to the right by the selective ß3 -adrenoceptor antagonist L-748,337 but unaffected by ß1 - and ß2 -adrenoceptor antagonists (atenolol and ICI-118,551 respectively). Mirabegron-induced relaxations were enhanced by the PDE4 inhibitor rolipram, and the agonist stimulated cAMP synthesis. Mirabegron also produced rightward shifts in urethral contractions induced by the α1 -adrenoceptor agonist phenylephrine. Schild regression analysis revealed that mirabegron behaves as a competitive antagonist of α1 -adrenoceptors in urethra, vas deferens and prostate (α1A -adrenoceptor, pA2  â‰… 5.6) and aorta (α1D -adrenoceptor, pA2  â‰… 5.4) but not in spleen (α1B -adrenoceptor). The affinities estimated for mirabegron in functional assays were consistent with those estimated in radioligand binding with human recombinant α1A - and α1D -adrenoceptors (pKi  â‰… 6.0). CONCLUSION AND IMPLICATIONS: The effects of mirabegron in urethral smooth muscle are the result of ß3 -adrenoceptor agonism together with α1A and α1D -adrenoceptor antagonism.

Bisphenol A inhibits duodenal movement ex vivo of rat through nitric oxide-mediated soluble guanylyl cyclase and α-adrenergic signaling pathways.

The gastrointestinal tract is directly exposed to bisphenol A (BPA)-tainted foods and beverages stored in polycarbonate plastic containers. The effect of BPA on the movement of small intestine has not been reported until now. We report here the effect of BPA on the movement of the duodenum ex vivo in a rat model. We found significant inhibition of duodenal movement by BPA (10-320 µM). We suggest that BPA-induced inhibition of duodenal movement might be due to the suppression of stimulatory and/or activation of inhibitory motor neurons in enteric plexuses innervating the longitudinal and circular visceral smooth muscle cells in the duodenal wall. We observed a significant reversal of BPA-induced depression of duodenal movement by methylene blue, a soluble guanylyl cyclase blocker and N-ω-nitro-L-arginine methyl ester, a nitric oxide (NO) synthase inhibitor; but significant potentiation of the movement by sodium nitroprusside, a NO donor. From the results, we may suggest that BPA-induced inhibition of the movement might be partially due to activation of inhibitory motor neurons that secrete NO, a relaxant, on to smooth muscle cells. Furthermore, we found significant reversal of BPA-induced depression of the movement in phentolamine, an α-adrenergic receptor blocker, pretreated preparation. This result proves that norepinephrine secreting motor neurons may also be involved in BPA-induced inhibition of the movement. From the results, we conclude that BPA inhibits the movement of the duodenum through NO-mediated soluble guanylyl cyclase and α-adrenergic signaling pathways in visceral smooth muscle cells.

[SUPRESSION MECHANISMS OF ANGIOTENSIN II-INDUCED VASCULAR SPASM OF ISOLATED RAT PORTAL VEIN IN VITRO].

On the basis of the experimental model of angiotensin (Ang) II-induced vasoconstriction by means of the pharmacological agents with various mechanisms of vasoactive action (including verapamil, lidocaine, papaverine, atropine, phentolamine) dependence of Ang II-mediated vascular effect on the state of L-type voltage-dependent calcium channels, voltage-gated sodium channels, phosphodiesterase 3, acetylcholine muscarinic receptors, α-adrenergic receptors were investigated. As a result of the detailed studying of mechanisms of Ang II-mediated vascular effect, it was confirmed that Ang II-induced contraction of isolated rat portal vein depends on the influx of extracellular Ca 2+ through L-type voltage-dependent calcium channels, is less dependent on the phosphodiesterase 3 activity, but it's not dependent on the functional properties of voltage-gated sodium channels, acetylcholine muscarinic receptors and α-adrenergic receptors.

Role of Opioid Receptors Signaling in Remote Electrostimulation--Induced Protection against Ischemia/Reperfusion Injury in Rat Hearts.

AIMS: Our previous studies demonstrated that remote electro-stimulation (RES) increased myocardial GSK3 phosphorylation and attenuated ischemia/ reperfusion (I/R) injury in rat hearts. However, the role of various opioid receptors (OR) subtypes in preconditioned RES-induced myocardial protection remains unknown. We investigated the role of OR subtype signaling in RES-induced cardioprotection against I/R injury of the rat heart. METHODS & RESULTS: Male Spraque-Dawley rats were used. RES was performed on median nerves area with/without pretreatment with various receptors antagonists such as opioid receptor (OR) subtype receptors (KOR, DOR, and MOR). The expressions of Akt, GSK3, and PKCε expression were analyzed by Western blotting. When RES was preconditioned before the I/R model, the rat's hemodynamic index, infarction size, mortality and serum CK-MB were evaluated. Our results showed that Akt, GSK3 and PKCε expression levels were significantly increased in the RES group compared to the sham group, which were blocked by pretreatment with specific antagonists targeting KOR and DOR, but not MOR subtype. Using the I/R model, the duration of arrhythmia and infarct size were both significantly attenuated in RES group. The mortality rates of the sham RES group, the RES group, RES group + KOR antagonist, RES group + DOR/MOR antagonists (KOR left), RES group + DOR antagonist, and RES group + KOR/MOR antagonists (DOR left) were 50%, 20%, 67%, 13%, 50% and 55%, respectively. CONCLUSION: The mechanism of RES-induced myocardial protection against I/R injury seems to involve multiple target pathways such as Akt, KOR and/or DOR signaling.

Noradrenergic modulation of itch transmission in the spinal cord.

Inhibition of both itching and scratching is important in the treatment of chronic pruritic diseases, because itching has a negative impact on quality of life and vigorous scratching worsens skin conditions. Pharmacological modulation of itch transmission in the dorsal horn is an effective way to inhibit both itching and scratching in pruritic diseases. Pruriceptive transmission in the spinal dorsal horn undergoes inhibitory modulation by the descending noradrenergic system. The noradrenergic inhibition is mediated by excitatory α1-adrenoceptors located on inhibitory interneurons and inhibitory α2-adrenoceptors located on central terminals of primary sensory neurons. The descending noradrenergic system and α-adrenoceptors in the dorsal horn are potential targets for antipruritic drugs.