title: Mechanisms of nitric oxide-mediated, neurogenic vasodilation in mesenteric resistance arteries of toad Bufo marinus.
abstract: This study determined the role of nitric oxide (NO) in neurogenic vasodilation in mesenteric resistance arteries of the toad Bufo marinus. NO synthase (NOS) was anatomically demonstrated in perivascular nerves, but not in the endothelium. ACh and nicotine caused TTX-sensitive neurogenic vasodilation of mesenteric arteries. The ACh-induced vasodilation was endothelium-independent and was mediated by the NO/soluble guanylyl cyclase signaling pathway, inasmuch as the vasodilation was blocked by the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one and the NOS inhibitors N(omega)-nitro-l-arginine methyl ester and N(omega)-nitro-l-arginine. Furthermore, the ACh-induced vasodilation was significantly decreased by the more selective neural NOS inhibitor N(5)-(1-imino-3-butenyl)-l-ornithine. The nicotine-induced vasodilation was endothelium-independent and mediated by NO and calcitonin gene-related peptide (CGRP), inasmuch as pretreatment of mesenteric arteries with a combination of N(omega)-nitro-l-arginine and the CGRP receptor antagonist CGRP-(8-37) blocked the vasodilation. Clotrimazole significantly decreased the ACh-induced response, providing evidence that a component of the NO vasodilation involved Ca(2+)-activated K(+) or voltage-gated K(+) channels. These data show that NO control of mesenteric resistance arteries of toad is provided by nitrergic nerves, rather than the endothelium, and implicate NO as a potentially important regulator of gut blood flow and peripheral blood pressure.
authors.affiliation: School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia. bjennin6@uthsc.edu
authors.forename: Brett L
authors.initials: BL
authors.lastname: Jennings
authors.forename: John A
authors.initials: JA
authors.lastname: Donald
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D002024:Bufo marinus; D006152:Cyclic GMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D008084:Lipoxygenase / Q000378:metabolism; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000294:innervation* / Q000502:physiology*; D009213:Myography; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D026941:Sodium Channel Blockers; D014665:Vasodilator Agents; D009569:Nitric Oxide; D013779:Tetrodotoxin; D009538:Nicotine; D008084:Lipoxygenase; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D011451:Prostaglandin-Endoperoxide Synthases; D009252:NADPH Dehydrogenase; D006152:Cyclic GMP; D000109:Acetylcholine