title: Effects of calcium antagonists on the nitrergic nerve function in canine corpus cavernosum.
abstract: Effects of calcium antagonists on nitrergic nerve function were examined in the isolated canine corpus cavernosum. In the cavernous strips precontracted with phenylephrine, transmural electrical stimulation elicited frequency-dependent (2 - 5 Hz) relaxations that were abolished by N(G)-nitro-L-arginine (10(-5) M), a nitric oxide (NO) synthase inhibitor; 1H[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ, 10(-6) M), a soluble guanylate cyclase inhibitor; and tetrodotoxin (3 x 10(-7) M). The relaxations were not affected by treatment with nifedipine or nicardipine (10(-8) - 10(-6) M), L-type specific calcium channel inhibitors, but were significantly inhibited by amlodipine or cilnidipine, inhibitors of L- plus N-type calcium channels, in a concentration-related manner (10(-7) - 10(-6) M). All of the inhibitors used did not affect the relaxations induced by exogenous NO (acidifed NaNO2). These findings suggest that N-type, but not L-type, calcium channels are responsible for increasing cytosolic free calcium, a prerequisite for the synthesis of NO, in the nitrergic dilator nerves innervating the corpus cavernosum.
authors.affiliation: Department of Pharmacology, Shiga University of Medical Science, Seta, Ohtsu, Japan. okamura@belle.shiga-med.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Okamura
authors.forename: H
authors.initials: H
authors.lastname: Fujioka
authors.forename: K
authors.initials: K
authors.lastname: Ayajiki
mesh_terms: D017311:Amlodipine / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004285:Dogs; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation; D009543:Nifedipine / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000502:physiology; D010413:Penis / Q000187:drug effects* / Q000294:innervation* / Q000502:physiology; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D017311:Amlodipine; D009569:Nitric Oxide; D020866:omega-Conotoxin GVIA; D019001:Nitric Oxide Synthase; D009543:Nifedipine