title: Conditions permitting suppression of stretch-induced and vasoconstrictor tone by basal nitric oxide activity in porcine cerebral artery.
abstract: This study examined the ability of basal nitric oxide activity to suppress intrinsic and vasoconstrictor tone in isolated rings of porcine cerebral artery. Following stretch of approximately 1 g, N(G)-nitro-L-arginine methyl ester (L-NAME, 100 microM) produced a rise in tone in endothelium-containing but not endothelium-denuded rings. Thus, intrinsic tone was present and was powerfully suppressed by basal nitric oxide activity. Nevertheless, when concentration-response curves were constructed to U46619 and 5-hydroxytryptamine (5-HT), no endothelium-dependent depression of vasoconstriction was observed. It therefore appeared that basal nitric oxide activity was able to suppress intrinsic but not vasoconstrictor tone in these vessels. Stretch-tension curves generated following the application of stretch over the range 0 - 5. 5 g on endothelium-denuded rings showed that tension was stretch-induced. Experiments conducted in the presence of L-NAME (100 microM) revealed that the level of tone present in endothelium-containing rings was substantially higher than in endothelium-denuded rings across the entire range of stretch. When endothelium-containing and endothelium-denuded rings were set at similar levels of stretch-induced tone, rather than similar levels of stretch, the presence of the endothelium now depressed significantly vasoconstrictor responses to U46619 and 5-HT. Thus, when endothelium-containing and endothelium-denuded rings of porcine cerebral artery are set at similar points along their respective stretch-tension curves, rather than at similar levels of stretch, basal nitric oxide activity can be seen to inhibit both stretch-induced and vasoconstrictor tone.
authors.affiliation: Division of Neuroscience & Biomedical Systems, Institute of Biomedical & Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ.
authors.forename: S J
authors.initials: SJ
authors.lastname: Wallis
authors.forename: W
authors.initials: W
authors.lastname: Martin
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D002536:Cerebral Arteries / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009129:Muscle Tonus / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D012701:Serotonin / Q000494:pharmacology; D013552:Swine; D014661:Vasoconstriction / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D012701:Serotonin; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester