Involvement Of Adrenergic Receptors Research Articles

Investigation of anti-nociceptive, anti-inflammatory potential and ADMET studies of pure compounds isolated from Isodon rugosus Wall. ex Benth.

The strong ethnopharmacological utilization of Isodon rugosus Wall. Ex. Benth is evident in the treatment of several types of pain and inflammation, including toothache, earache, abdominal pain, gastric pain, and generalized body pain and inflammation. Based on this background, the antinociceptive effects of the crude extract, various fractions, and essential oil have been reported previously. In this research work, we isolate and characterize pure bioactive compounds from I. rugosus and evaluate possible mechanisms using various in vivo and in vitro models. The pure compounds were analyzed for analgesic and anti-inflammatory activities through various assays. The column chromatography of the chloroform fraction of I. rugosus led to the identification of two pure compounds, i.e., 1 and 2. Compound 1 demonstrated notable inhibition (62% writhing inhibition, 72.77% COX-2 inhibition, and 76.97% 5-LOX inhibition) and anti-inflammatory potential (>50% paw edema inhibition at various intervals). The possible mechanism involved in antinociception was considered primarily, a concept that has already been elucidated through the application of naloxone (an antagonist of opioid receptors). The involvement of adrenergic receptors was investigated using a hot plate model (an adrenergic receptor antagonist). The strong ethnomedicinal analgesic background of I. rugosus, supported by previous reports and current observations, leads to the conclusion that I. rugosus is a potential source of antinociceptive and anti-inflammatory bioactive compounds. It may be concluded from the results that the isolated analgesic compounds of I. rugosus may be a possible alternative remedy for pain and inflammation management with admirable efficacy and safety profiles.

Putative involvement of adrenergic receptors in regulation of mussel (Perna canaliculus) larval settlement

Settlement responses were investigated for mussel (Perna canaliculus) larvae after exposure to catecholamines and their precursor metabolites. Settlement and mortality assays were conducted in Petri plates with chemical treatments (L-phenylalanine, L-tyrosine, L-DOPA, dopamine hydrochloride and epinephrine at various concentrations) and controls. The proteinogenic amino acids L-phenylalanine and L-tyrosine were both effective inducers (~65%) of larval settlement at 10−5 mol l−1 compared with controls (4%). Exposure of larvae to L-DOPA, dopamine and epinephrine resulted in maximum settlement induction (50, 60 and 51%, respectively) at 10−5 mol l−1. Larval mortalities were low (comparable to controls) across all concentrations of L-phenylalanine and L-tyrosine treatments, whereas high mortalities (>60%) were observed for L-DOPA, dopamine and epinephrine at concentrations ≥ 10−4 mol l−1. Our results indicate that P. canaliculus larval settlement is under endogenous regulation by a catecholaminergic mechanism. Furthermore, the inductive effects of all tested metabolites in the epinephrine biosynthesis pathway point to a putative involvement of adrenergic-type receptors in the regulation of larval settlement in this mussel species.

Modulation of Adrenergic Signalling by Flavonoids in Cardioprotection

Dietary flavonoids are thought to contribute to the prevention of cardiovascular disease. Recently we showed that 2,3-dehydrosilybin (DHSB) attenuated cardiomyocyte damage following hypoxia/reoxygenation by modulating mitochondrial bioenergetics. The aim of the current study was to examine the effect of DHSB on isolated perfused rat heart and cardiomyocyte cell culture.Langendorff perfused rat hearts were used to investigate the response of Left ventricular developed pressure (LVDP), end-diastolic pressure (LVEDP) and contractility (dP/dtmax) to exposure to 10μM DHSB, 10μM quercetin, with 100nM bradykinin as a positive control. In vitro testing of mitochondrial network and involvement of adrenergic receptors was performed on cardiomyocyte cell cultures. Activation of signaling pathways in culture models was assessed via a CREB-Luciferase reporter system, western blotting and fluorescent Ca2+ probes.Quercetin treated hearts demonstrated no significant changes from controls. Bradykinin, as expected, caused vasodilation. DHSB, on the other hand, caused a prompt and dynamic elevation of LVEDP, heart rate and contractility along with enlargement and hardening of the organ and ruffling of the ventricular surface during perfusion. Contractility and heart rate were restored during washout in the DHSB group, while heart rate was reduced to half of the initial value. Pretreatment with propranolol abolished DHSB induced elevation of heart rate, LVEDP and contractility but not morphological changes. Western blots of signalosome fractions indicate that DHSB triggers signalosome formation. Morphological changes are also evident in the mitochondrial network. CREB reporter assays indicate that DHSB enhances transcription from the CRE promoter. Additionally, DHSB enhances isoproterenol, but not norepinephrine induced transcription from the CRE promoter. This effect was not inhibited by propranolol. The results suggest that DHSB interacts with the adrenergic signaling pathway, but not at the level of the adrenergic receptors.Supported by grants P301/11/0662, CZ.1.05/2.1.00/01.0030, and CZ.1.07/2.3.00/30.0041.

Evidence for a Critical Role of Catecholamines for Cardiomyocyte Lineage Commitment in Murine Embryonic Stem Cells

Catecholamine release is known to modulate cardiac output by increasing heart rate. Although much is known about catecholamine function and regulation in adults, little is known about the presence and role of catecholamines during heart development. The present study aimed therefore to evaluate the effects of different catecholamines on early heart development in an in vitro setting using embryonic stem (ES) cell-derived cardiomyocytes. Effects of catecholamine depletion induced by reserpine were examined in murine ES cells (line D3, αPIG44) during differentiation. Cardiac differentiation was assessed by immunocytochemistry, qRT-PCR, quantification of beating clusters, flow cytometry and pharmacological approaches. Proliferation was analyzed by EB cross-section measurements, while functionality of cardiomyocytes was studied by extracellular field potential (FP) measurements using microelectrode arrays (MEAs). To further differentiate between substance-specific effects of reserpine and catecholamine action via α- and β-receptors we proved the involvement of adrenergic receptors by application of unspecific α- and β-receptor antagonists. Reserpine treatment led to remarkable down-regulation of cardiac-specific genes, proteins and mesodermal marker genes. In more detail, the average ratio of ∼40% spontaneously beating control clusters was significantly reduced by 100%, 91.1% and 20.0% on days 10, 12, and 14, respectively. Flow cytometry revealed a significant reduction (by 71.6%, n = 11) of eGFP positive CMs after reserpine treatment. By contrast, reserpine did not reduce EB growth while number of neuronal cells in reserpine-treated EBs was significantly increased. MEA measurements of reserpine-treated EBs showed lower FP frequencies and weak responsiveness to adrenergic and muscarinic stimulation. Interestingly we found that developmental inhibition after α- and β-adrenergic blocker application mimicked developmental changes with reserpine. Using several methodological approaches our data suggest that reserpine inhibits cardiac differentiation. Thus catecholamines play a critical role during development.

Pharmacological properties of isoidide dinitrate.

Abstract Isoidide dinitrate is a more active vasodepressor agent in anaesthetised animals than either of its geometric isomers, isosorbide dinitrate and isomannide dinitrate. Isoidide dinitrate also has the greatest vasodilator action of the three isomers on the vascular system of the dog hind leg and is a more potent hypotensive agent than isosorbide dinitrate in hypertensive rats. The greater activity of isoidide dinitrate may be attributable to its higher oil: water partition coefficient or enhanced drug-receptor interaction resulting from the spatial positions of the nitrate groups or both factors. No evidence was found for involvement of adrenergic receptors in responses of vascular or intestinal smooth muscle to isoidide dinitrate.

Participation of α 2 Receptors in the Antinociceptive Activity of Quercetin

The present work was planned to evaluate the antinociceptive activity of quercetin, its site of action, and the involvement of adrenergic receptors in mediating the antinociceptive activity in thermal and chemonociceptive assays. Eight groups were employed in this study: Groups I, II, and III received quercetin alone in different doses, group IV animals were administered clonidine, group V animals were co-administered quercetin and clonidine, group VI animals were administered yohimbine 30 minutes prior to administratin of quercetin, group VII animals were administered yohimbine 30 minutes prior to co-administration of quercetin and clonidine, and group VIII animals were administered 0.5% carboxymethylcellulose in saline (vehicle for quercetin). The thermal nociception was measured by tail flick and hot plate methods. Quercetin produced a significant analgesic effect in a dose-dependent manner. Co-administration of low doses of quercetin and clonidine produced a synergistic analgesic effect. Pretreatment with yohimbine significantly reversed quercetin-as well as clonidine/quercetin combination-induced effects. The results of this study reveal that quercetin induces an antinociceptive effect and that this effect involves primarily the modulation of adrenergic pathways.

Absence of reduced platelet adenylate cyclase activity in Vietnam veterans with PTSD

Many studies have been devoted to an examination of radioligand receptor binding and postreceptor signal transduction in peripheral cells obtained from patients suffering from mood or anxiety disorders. Postreceptor signal transduction has been investigated by the use of agents that interact with the adenylate cyclase system at points distal to the receptor, such as aluminum chloride (AIC13) and sodium fluoride (NaF), which affect the guanyl nucleotidebinding (G) protein, and forskolin, which affects the catalytic (C) unit of the enzyme. Post-traumatic stress disorder (PTSD) is a member of the group of anxiety disorders which also includes generalized anxiety disorder, panic disorder, and obsessive-compulsive disorder. PTSD also shares phenomenological features with depression (Sierles et al 1983). Abnormalities in adenylate cyclase activity have been demonstrated in peripheral cells derived both from panic disorder patients (Charney et al 1989) and depressed patients (Ebstein et a11988; Kanof et al 1988). Recent evidence has indicated possible abnormalities at both the receptor and postreeeptor levels in platelets from PTSD patients. Perry et al (1987) found a reduction in alpha-2-adrenergic receptors in 11 Vietnam veterans with PTSD relative to agematched normal controls. This was due to a relative loss of sites labeled with low affinity by the antagonist 3H-rauwolscine, representing those sites coupled via the inhibitory G protein Gi to adenylate cyclase. The involvement of adrenergic receptors in PTSD has been recently reviewed (Lerer et al 1994). In a series of studies, our laboratory has investigated platelet adenylate cyclase in PTSD with mixed results. A first study (Lerer

Hypotensive and spasmolytic activities of ethanolic extract of Capparis cartilaginea

AbstractAn ethanolic extract of Capparis cartilaginea (CC) at a dose of 1–10 mg/kg caused a dose‐dependent fall in blood pressure and heart rate in anaesthetized rats. These effects were not blocked by atropine (1 mg/kg) and pretreatment with CC did not alter the pressor response to norepinephrine, indicating that the cardiovascular effects of CC are independent of cholinergic or adrenergic receptor involvement. In spontaneously beating guinea‐pig atria, CC induced a concentration‐dependent (0.1–1 mg/mL) decrease in force and rate of atrial contractions. In rabbit thoracic aorta, CC caused inhibition of norepinephrine or K+‐induced contractions. In guinea‐pig ileum, CC (1 mg/mL) inhibited submaximal contractions induced by acetylcholine, histamine or 5‐HT. Spontaneous contractions of rat uterus were also abolished when CC was added to the tissue bath at similar concentrations. These results suggest that the direct relaxant action of CC on myocardium and blood vessels may be responsible for its hypotensive and bradycardiac effects observed in the in vivo studies. Moreover, CC exhibits general spasmolytic activity in different smooth muscle preparations.

Alpha and Beta Adrenergic Receptor Involvement in Catecholamine-Induced Growth of Gram-Negative Bacteria

The effect of a number of adrenergic receptor agonists and antagonists on the growth of Escherichia coli and Yersinia enterocolitica was examined in order to delineate possible receptor mechanism(s) by which the catecholamines influence the growth of grain-negative bacteria. Neither α or β adrenergic receptor agonists or antagonists affected growth in a dose-dependent manner similar to that observed for norepinephrine. The physiological less active enantiomer of norepinephrine, (+)-norepinephrine, did not affect catecholamine-induced growth to a similar degree as that observed with the active enantiomer. These results suggest that a non-α, non-β adrenergic receptor mediated process may play a role in catecholamine-induced growth of gram-negative bacteria.

Participation of adrenoceptors in liver blood flow regulation in anesthetized dogs.

We evaluated involvement of adrenergic receptors in the responses of the hepatic vasculature to reduction either of portal venous flow or hepatic arterial inflow. Portal vein occlusion caused an increase in hepatic arterial blood flow (HAF) and decreases in hepatic arterial pressure (HAP) and hepatic arterial vascular resistance (HAR) in the intact group. After pretreatment with either yohimbine or prazosin, but not propranolol, occlusion of the portal vein produced a greater decrease in HAP as compared with that in the intact group. No significant changes in HAF, HAR, or hepatic tissue blood flow (HTF) occurred after the treatment. These results indicate that the compensatory response of the hepatic arterial vasculature to altered portal blood flow (PVF) is regulated independently of the intrahepatic adrenergic receptors. Hepatic arterial occlusion caused a significant decrease in portal venous pressure, PVF, and HTF. Portal venous vascular resistance (PVR) was reduced slightly, but not significantly. After pretreatment with either yohimbine or prazosin, but not propranolol, occlusion of the hepatic artery produced an opposite effect: to increase PVF and significantly decrease PVR. These results indicate that intrahepatic alpha-adrenoceptors participate in the regulation of portal vascular tone to maintain portal vein pressure at a steady level, when inflow from the hepatic artery is reduced.

Absence of ??-Adrenergic Receptor Involvement in Cerebrovascular Dilation by Halothane in Monkeys

We determined, in monkeys, whether halothane-induced cerebrovascular dilation is mediated by beta-adrenergic receptors and whether cerebrovascular tone progressively returns to baseline values during prolonged halothane anesthesia. Total cerebral blood flow (CBF), cerebral perfusion pressure, plasma halothane concentration, and arterial blood gas tensions and pH were measured in 14 rhesus monkeys mechanically ventilated with 0.5% (inspired) halothane, 33% O2 and balance N2O. Halothane was increased to 2.0% and the measurements repeated 30 and 60 min later. Then either 0.9% NaCl (controls n = 6) or propranolol (n = 8), 1.0 mg/kg was infused intravenously over 10 min, and the measurements repeated at 70, 90, 120, and 150 min. After 30 min at 2.0% halothane, CBF increased in the controls by 50% (P less than 0.05) from 92 +/- 8 (mean +/- SD) to 137 +/- 39 ml X 100 g-1 X min-1 and in the propranolol group by 30% (P less than 0.05) from 106 +/- 33 to 137 +/- 28 ml X 100 g-1 X min-1. After 2.5 hr of 2.0% halothane anesthesia, CBF remained elevated above baseline levels, but by only 28 and 23% in the control and propranolol groups, respectively. Cerebrovascular resistance was identical in both groups (0.55 +/- 0.33 vs 0.53 +/- 0.13 mm Hg X ml-1 X 100 g 1 X min 1). The results show that there is only a 10-20% return of CBF toward baseline levels after up to 2.5 hr of 2% halothane anesthesia. The results also indicate that halothane-induced cerebrovascular dilation is not mediated by beta-adrenergic receptors.

Absence of ??-Adrenergic Receptor Involvement in Cerebrovascular Dilation by Halothane in Monkeys

We determined, in monkeys, whether halothane-induced cerebrovascular dilation is mediated by β-adrenergic receptors and whether cerebrovascular tone progressively returns to baseline values during prolonged halothane anesthesia. Total cerebral blood flow (CBF), cerebral perfusion pressure, plasma halothane concentration, and arterial blood gas tensions and pH were measured in 14 rhesus monkeys mechanically ventilated with 0.5% (inspired) halothane, 33% O2 and balance N2O. Halothane was increased to 2.0% and the measurements repeated 30 and 60 min later. Then either 0.9% NaCl (controls n = 6) or propranolol (n = 8), 1.0 mg/kg was infused intravenously over 10 min, and the measurements repeated at 70, 90, 120, and 150 min. After 30 min at 2.0% halothane, CBF increased in the controls by 50% (P < 0.05) from 92 ± 8 ( ± sd) to 137 ± 39 ml·100 g−1·min−1 and in the propranolol group by 30% (P < 0.05) from 106 ± 33 to 137 ± 28 ml·100 g−1·min−1. After 2.5 hr of 2.0% halothane anesthesia, CBF remained elevated above baseline levels, but by only 28 and 23% in the control and propranolol groups, respectively. Cerebrovascular resistance was identical in both groups (0.55 ± 0.33 vs 0.53 ± 0.13 mm Hg·ml−1·100 g−1·min−1). The results show that there is only a 10–20% return of CBF toward baseline levels after up to 2.5 hr of 2% halothane anesthesia. The results also indicate that halothane-induced cerebrovascular dilation is not mediated by β-adrenergic receptors.

Alpha 1-adrenergic receptor involvement in norepinephrine-ethanol inhibition of rat brain Na+ -K+ ATPase and in ethanol tolerance.

Norepinephrine (NE) sensitization of rat brain Na+ -K+ ATPase to ethanol (EtOH) inhibition appears to be mediated by alpha 1-adrenoreceptors, since it was reversed by prazosin and WB-4101 (alpha 1-receptor antagonists) in a concentration-dependent manner, but not by yohimbine and piperoxan (alpha 2-receptor antagonists). In addition, clonidine (alpha 2-agonist) and methoxamine (central receptor type uncertain) produced very little sensitization. Chronic EtOH administration to rats for 3 weeks produced tolerance to the hypothermic effect of test doses of EtOH (3 g/kg, i.p.) and a decreased inhibitory effect of NE + EtOH on the enzyme in vitro. This inhibition was still prevented by prazosin and WB-4101. However, the binding of tritiated WB-4101 and prazosin to brain membrane preparations from control and EtOH-tolerant rats revealed that the maximum number of binding sites (Bmax) and the dissociation constant (KD) of alpha 1-adrenoreceptors were decreased after tolerance development. These changes in numbers and binding properties of alpha 1-adrenoreceptors probably account for the decreased NE sensitization of the ATPase to EtOH inhibition in preparations from EtOH-tolerant rats.

Involvement of adrenergic receptors in skeletal muscle metabolism of the cold-adapted rat.

Hind-limb perfusion was used to investigate alterations of alpha and beta receptor-mediated metabolic effects in cold-adapted (CA) rats. The response to beta receptor stimulation by isoproterenol in the isolated hind-limbs of CA rats was slightly diminished. Oxygen consumption and lactate production were reduced in CA rats after beta receptor stimulation. Noradrenalin infusion caused less vasoconstriction in CA rats than in the controls (CO). Desensitization of alpha and beta receptors due to chronic sympathetic overstimulation may be the underlying cause of these observations. Compared with the controls, metabolism was enhanced in perfused hind-limbs of CA rats with an active nervous system. Decreased vascular resistance due to the lower perfusion pressure in CA rats might contribute to this increased metabolism.

Adrenergic stimulation of fertilizing ability in hamster spermatozoa.

Hamster spermatozoa, preincubated for 3 h in a culture medium containing bovine serum albumin (BSA) and a protein-free ultrafiltrate of a bovine adrenal cortex preparation, were unable to fertilize cumulus-free eggs. In contrast, if the culture medium also contained a protein-free ultrafiltrate of a bovine adrenal medulla preparation, 92% of the inseminated eggs were fertilized within 2 h. Replacement of the adrenal medulla preparation with 20.0 pM (-)-epinephrine (BSA and the adrenal cortex preparation also present) resultedin 85% of the inseminated eggs being fertilized. If 20.0 pM (-)-phenylephrine, an 3-adrenergic agonist or 20.0 pM (-)-isoproterenol, a j3-adrenergic agonist, was used in place of epinephrine, the percentage of fertilized eggs was 11% and 50%, respectively. With both phenylephrine and isoproterenol present. 90% of the eggs were fertilized. Furthermore, fertilization in the presence of 20.0 pM (-)-epinephrine could be inhibited by equimolar concentrations of either phentolamine, an n-adrenergic antagonist, (0% fertilization) or (-)-propranolol, a 13-adrenergic antagonist, (18% fertilization). These results, together with our previous work, suggest the involvement of adrenergic receptors in the development of the fertilizing ability of hamster spermatozoa in vitro.

Involvement of adrenergic receptors in central vagus activity

In pentobarbital anaesthetized dogs pretreated with the β-blocking agent Kö 592, repeated i.v. injections of angiotensin increased blood pressure and produced a vagus-mediated, reflex bradycardia. Intracisternal (i.ci.) injections of clonidine 1 mg/kg (an α-receptor stimulating agent), significantly increased the reflex bradycardia and this effect was significantly antagonized by phentolamine, 0.5 mg/kg, i.ci. (an α-receptor blocking agent). The results indicate involvement of adrenergic receptors in central vagus activity.