The role of nitric oxide on the relaxations of rabbit corpus cavernosum induced by Androctonus australis and Buthotus judaicus scorpion venoms.
In this study, we have investigated the relaxing effects of both Androctonus australis venom (AAV) and Buthotus judaicus venom (BJV) on the rabbit corpus cavernosum (RbCC) smooth muscle strips. The RbCC strips were mounted in a cascade system and superfused with warmed and gassed Krebs solution. The nitric oxide (NO) synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 10microM), but not D-NAME (10microM), significantly inhibited the RbCC relaxations induced by acetylcholine (ACh, 0.6nmol), AAV (30microg) and BJV (30microg). Subsequent infusion of L-arginine (300microM), but not of D-arginine (300microM), partially restored the relaxations evoked by these agents. The brain NO synthase inhibitor 7-nitroindazole (7-NI, 10microM) also inhibited the relaxant responses elicited by the scorpion venoms. The guanylyl cyclase inhibitors methylene blue (MB, 30microM) and 1H-[1,2,4] oxadiazolo [4,3,-alquinoxalin-1-one] (ODQ, 10microM) virtually abolished the relaxations induced by either AAV or BJV. The infusion of muscarinic receptor antagonists such as scopolamine and atropine (1microM, each) completely abolished the ACh-induced relaxations but had no effect on those evoked by the scorpion venoms. The Na(+) channel blocker tetrodotoxin (1microM) prevented the relaxations evoked by both AAV and BJV. Thus, NO released from nitrergic nerve fibres mediates the relaxations elicited by AAV and BJV in the rabbit cavernosal tissue.
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Department of Pharmacology, Faculty of Medical Sciences, UNICAMP, P. O. Box 6111, 13081-970, (SP), Campinas, Brazil. cleber@bestway.com.br
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Antunes
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D000109:Acetylcholine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007191:Indazoles / Q000494:pharmacology; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D010413:Penis / Q000187:drug effects; D011817:Rabbits; D012601:Scopolamine / Q000494:pharmacology; D012604:Scorpion Venoms / Q000037:antagonists & inhibitors / Q000201:enzymology / Q000494:pharmacology*; D013237:Stereoisomerism; D013779:Tetrodotoxin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007191:Indazoles; D018727:Muscarinic Antagonists; D012604:Scorpion Venoms; D009569:Nitric Oxide; D013779:Tetrodotoxin; D001285:Atropine; D012601:Scopolamine; D000109:Acetylcholine; C080122:7-nitroindazole; D019331:NG-Nitroarginine Methyl Ester