title: Monkey corpus cavernosum relaxation mediated by NO and other relaxing factor derived from nerves.
abstract: Isolated monkey corpus cavernosum muscle strips contracted with prostaglandin F2 alpha and treated with prazosin responded to transmural electrical stimulation with frequency-related relaxations that were abolished by tetrodotoxin. The nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NNA) significantly attenuated but did not abolish the response; L-arginine reversed the inhibition. The neurogenic relaxation was not influenced in the strips treated with atropine or calcitonin gene-related peptide (CGRP)-(8-37), a CGRP-receptor antagonist, and those desensitized to vasoactive intestinal polypeptide (VIP) or pituitary adenylate cyclase-activating polypeptide (PACAP). Nerve fibers containing NADPH diaphorase were histochemically demonstrated in cavernous tissues. The relaxant response resistant to the NO synthase inhibitor was abolished by high K+ and tetrabutylammonium but was unaffected by glibenclamide, charybdotoxin, apamin, ouabain, SKF-525a, a cytochrome P-450 inhibitor, and oxyhemoglobin. It is concluded that neurogenic relaxations of monkey corpus cavernosum muscle is associated partly with NO released as a neurotransmitter and that other relaxing factor(s) possibly responsible for K+ channel opening also participates; however, the type of K+ channel involved is not determined. Acetylcholine, VIP, CGRP, PACAP, and the Na+ pump do not seem to be involved in the neurogenic relaxation.
authors.affiliation: Department of Pharmacology, Shiga University of Medical Science, Ohtsu, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Okamura
authors.forename: K
authors.initials: K
authors.lastname: Ayajiki
authors.forename: N
authors.initials: N
authors.lastname: Toda
mesh_terms: D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008251:Macaca / Q000502:physiology*; D008297:Male; D009126:Muscle Relaxation / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D009420:Nervous System / Q000378:metabolism; D009424:Nervous System Physiological Phenomena; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D010410:Penile Erection / Q000502:physiology*; D010413:Penis / Q000294:innervation* / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase