Neuronal pathway involved in nitric oxide-mediated descending relaxation in rat ileum.
The neuronal pathway that initiates nitric oxide-mediated descending relaxation in rat ileum was studied. The descending relaxation, which was suggested to be mediated by nitric oxide from our previous study, was selectively inhibited by 5-HT3 receptor antagonists. It was also inhibited by a nicotinic acetylcholine receptor antagonist. Exogenous 5-hydroxytryptamine (5-HT) and a selective 5-HT3 receptor agonist induced dose-dependent relaxation of ileal circular muscle. 5-HT-induced relaxation was selectively inhibited by 5-HT3 receptor antagonists. Nicotine also induced relaxation of the circular muscle, and its effect was inhibited by 5-HT3 receptor antagonists. 5-HT and nicotine increased the cyclic GMP content of the ileal tissue. Nitro-L-arginine inhibited the increases induced by both compounds in the cyclic GMP content, and a 5-HT3 receptor antagonist also inhibited that induced by nicotine. These results indicate that activation of a cholinergic neuron-5-HT neuron pathway initiates nitric oxide-mediated descending relaxation in rat ileum.
Kanada
A
A
Department of Veterinary Pharmacology, College of Agriculture, University of Osaka Prefecture, Sakai, Japan.
Hosokawa
M
M
Suthamnatpong
N
N
Maehara
T
T
Takeuchi
T
T
Hata
F
F
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D018680:Cholinergic Antagonists; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007082:Ileum / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D007211:Indoles / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019335:Nitroarginine; D051381:Rats; D017208:Rats, Wistar; D011950:Receptors, Cholinergic / Q000502:physiology*; D011985:Receptors, Serotonin / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology; D000077526:Tropisetron
D018680:Cholinergic Antagonists; D007211:Indoles; D011950:Receptors, Cholinergic; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D014326:Tropanes; D019335:Nitroarginine; D009569:Nitric Oxide; D012701:Serotonin; D000077526:Tropisetron; D009538:Nicotine; D001120:Arginine; D006152:Cyclic GMP; C042253:bemesetron