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Characterization of the potassium channels involved in EDHF-mediated relaxation in cerebral arteries

1. In the presence of N(G)-nitro-L-arginine (L-NOARG, 0.3 mM) and indomethacin (10 μM), the relaxations induced by acetylcholine and the calcium (Ca) ionophore A23187 are considered to be mediated by endothelium-derived hyperpolarizing factor (EDHF) in the guinea-pig basilar artery. 2. Inhibitors of adenosine 5'-triphosphate (ATP)-sensitive potassium (K)-channels (K(ATP); glibenclamide, 10 μM), vo

Effects of cytochrome P450 inhibitors on EDHF-mediated relaxation in the rat hepatic artery

1. The possibility that the endothelium-derived hyperpolarising factor (EDHF) in the rat hepatic artery is a cytochrome P450 mono-oxygenase metabolite of arachidonic acid was examined in the present study. In this preparation, acetylcholine elicits EDHF-mediated relaxations in the presence of the nitric oxide (NO) synthase and cyclo-oxygenase inhibitors N(ω)-nitro-L-arginine (L-NOARG) and indometh

Role of potassium channels in endothelium-dependent relaxation resistant to nitroarginine in the rat hepatic artery

1. In the presence of indomethacin (IM, 10 μM) and N(ω)-nitro-L-arginine (L-NOARG, 0.3 mM), acetylcholine (ACh) induces an endothelium-dependent smooth muscle hyperpolarization and relaxation in the rat isolated hepatic artery. The potassium (K) channel inhibitors, tetrabutylammonium (TBA, 1 mM) and to a lesser extent 4-aminopyridine (4-AP, 1 mM) inhibited the L-NOARG/IM-resistant relaxation induc

Effects of cytochrome P450 inhibitors on potassium currents and mechanical activity in rat portal vein

1. The effects of the cytochrome P450 inhibitors, proadifen, clotrimazole and 17-octadecynoic acid (17-ODYA) on K-currents in freshly-isolated single cells derived from rat portal vein and on mechanical activity in whole veins were studied. 2. When cells were stepped from -90 mV to a series of test potentials (from -80 to +50 mV), a delayed rectifier current (I(K(V))) and an A-type current ((IK(A)

NANC neurotransmission in lamina propria of the rabbit urethra : regulation by different subsets of calcium channels

Electrical field stimulation (EFS) of the rabbit urethral lamina propria elicited a frequency‐dependent non‐adrenergic, non‐cholinergic (NANC) relaxation, which was abolished by NΩ–nitro‐L‐arginine (l‐NOARG). Ω‐Conotoxin GVIA, a selective blocker of N‐type voltage‐operated calcium channels (VOCCs), and Ω‐conotoxin MVIIC (blocker of N‐ and Q‐type VOCCs) inhibited the NANC relaxation, and the inhibi

Regional differences in endothelium‐dependent relaxation in the rat : contribution of nitric oxide and nitric oxide‐independent mechanisms

Relaxant effects of acetylcholine (ACh), histamine, calcitonin gene‐related peptide (CGRP) and the calcium ionophore A23187 were examined in rat femoral (Ø ≅ 0.2 mm), mesenteric (0.2 mm), intrarenal (0.2 mm) and hepatic (0.3 mm) arteries, and aorta (2 mm). Acetylcholine elicited an endothelium‐dependent relaxation in all arteries. Histamine induced an endothelium‐dependent relaxation in aorta, and

Endothelium‐dependent relaxation resistant to N/ω‐nitro‐L‐arginine in the rat hepatic artery and aorta

Nitric oxide (NO)‐independent pathways contributing to acetylcholine (ACh)‐induced relaxation were examined in the rat isolated hepatic artery and aorta at low and high levels of precontraction induced by phenylephrine (PhE). In the hepatic artery, the ACh‐induced relaxation was unaffected by the NO synthase inhibitors Nw‐nitro‐L‐arginine (L‐NOARG, 0.3 mM) and Nω‐nitro‐L‐arginine methyl ester (0.1

Light–dependent effects of zinc protoporphyrin IX on endothelium–dependent relaxation resistant to NoM–nitro–L–arginine

Acetylcholine (ACh) induces an Nω–nitro–L–arginine (L–NOARG)–resistant relaxation and hyperpolarization in the rat isolated hepatic artery. The possibility that carbon monoxide (CO) produced by haem oxygenase (HO) is an endogenous mediator of this response was investigated. Exogenously applied CO evoked a concentration–dependent relaxation, and the CO ‘scavenger’ oxyhaemoglobin (10μM) reduced the

The endothelium mediates a nitric oxide‐independent hyperpolarization and relaxation in the rat hepatic artery

The rat hepatic artery responds to acetylcholine (ACh) with an endothelium‐dependent relaxation, which is unaffected by nitric oxide (NO) synthase and cyclooxygenase inhibition. The purpose of this study was to investigate whether the NO‐independent relaxation is caused by hyperpolarization of the smooth muscle cells. In vessels with endothelium ACh induced a hyperpolarization in the presence of 0

Effects of ω‐conotoxin on adrenergic, cholinergic and NANC neurotransmission in the rabbit urethra and detrusor

The effects of ω‐conotoxin GVIA (an inhibitor of N‐type voltage‐operated calcium channels; VOCCs) were compared on adrenergic, cholinergic and non‐adrenergic, non‐cholinergic (NANC) responses induced by electrical field stimulation (EFS) in the rabbit urethra and detrusor. EFS induced a relaxation in urethral smooth muscle and lamina propria precontracted by arginine vasopressin (AVP). The relaxat

Calcium Antagonistic Properties of the Sesquiterpene T‐Cadinol and Related Substances : Structure‐Activity Studies

The calcium antagonistic properties of (+)‐T‐cadinol, some of its stereoisomers and related terpenes were investigated in both functional and radioligand binding studies, and the effects were compared with those of the dihydropyridine calcium antagonist (±)‐nimodipine. In the isolated rat aorta, the terpenes relaxed contractions induced by 60 mM K+ more potently than those induced by phenylephrine

Calcium Antagonistic Properties of the Sesquiterpene T‐Cadinol : A Comparison with Nimodipine in the Isolated Rat Aorta

Abstract: (+)‐T‐Cadinol is a sesquiterpene with smooth muscle relaxing properties. In the isolated rat aorta, T‐cadinol relaxed contractions induced by 60 mM K+ in a concentration‐dependent fashion. The dihydropyridine calcium antagonist nimodipine was approximately 4,000 times more potent than T‐cadinol. While both drugs nearly abolished the K+‐induced contractions, they only partially relaxed co

Inhibitory effects of the sesquiterpene T‐cadinol on contractile responses in the isolated guinea‐pig ileum

The smooth muscle relaxing effect of the sesquiterpene T‐cadinol, isolated from scented myrrh (resin of Commiphora guidottii Chiov., Burseraceae), was investigated. The compound inhibited the contractile responses in the isolated guinea‐pig ileum to histamine, carbachol, Ba2+ and K+ in a concentration dependent and reversible manner. The antagonism of the receptor‐mediated contractions induced by

Some substances with proposed digitalis-like effects evaluated on platelet functions sensitive for cardiac glycosides

1. 1. The effects of progresterone, corticosterone 21-acetate, chlormadinone acetate, dehydroepi-androsterone 3-sulfate and lysophosphatidylcholine were tested on 86Rb-uptake, 3H-5-HT-uptake, ADP-induced aggregation and 5-HT-induced shape change in human platelets. Ouabain and digoxin were used for reference. 2. 2. Ouabain and digoxin 10-5 M inhibited 86Rb-uptake by more than 85%, and chlormadinon

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Cette étude propose une analyse de la proportion d’élèves suédois qui étudientle français au collège et présente une réflexion plus générale sur la situationde l’enseignement du français en Suède. À partir de données statistiques de labase de données SIRIS, mise à disposition publique par la Direction nationale desÉtablissements scolaires, les résultats montrent que, même si la proportion d’élèves

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There are directions of interpretation with which some researchers may disagree. But it would be difficult for someone to point to rigidities, idiosyncracies or dangerous arguments. In fact, the demonstrations of Ion Pop meet the conditions for verifying the degree of science stated by an epistemologist such as Karl Popper. Any hypothesis has to be checked but also contradicted. Any theoretical en