Suppression by NG-nitro-L-arginine of relaxations induced by non-adrenergic, non-cholinergic nerve stimulation in dog duodenal longitudinal muscle.
In dog duodenal longitudinal muscle strips, transmural electrical stimulation (10 Hz, 15 sec) elicited a transient contraction, which was abolished by tetrodotoxin and atropine but potentiated by treatment with NG-nitro-L-arginine (L-NA), a nitric oxide (NO) synthesis inhibitor. The potentiation was reversed by L-arginine but not by its D-enantiomer. Acetylcholine-induced contractions were not influenced by L-NA. After treatment with atropine, the electrical neural stimulation relaxed the muscle strips partially contracted with bradykinin, the relaxation being abolished by tetrodotoxin and suppressed by L-, but not D-, NA. L-arginine reversed the L-NA-induced inhibition. Oxyhemoglobin abolished the relaxation caused by nerve stimulation and NO. The neurally-induced relaxation was not attenuated by adrenoceptor antagonists and indomethacin. It is concluded that electrical stimulation of non-adrenergic, non-cholinergic nerves relaxes dog duodenal smooth muscle, due possibly to NO produced upon neural excitation, and potentiation by L-NA of the contractile response to cholinergic nerve stimulation, would be derived from elimination of the neurally-induced relaxation.
Toda
N
N
Department of Pharmacology, Shiga University of Medical Sciences, Ohtsu, Japan.
Tanobe
Y
Y
Baba
H
H
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D004285:Dogs; D004386:Duodenum; D004558:Electric Stimulation; D005260:Female; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D019335:Nitroarginine; D013779:Tetrodotoxin / Q000494:pharmacology
D019335:Nitroarginine; D009569:Nitric Oxide; D013779:Tetrodotoxin; D001285:Atropine; D001120:Arginine