Autoinhibition of acetylcholine output from cholinergic nerves through activation of muscarinic receptors in the guinea-pig ileum and circular muscle preparations
1990
Takewaki, T. (Gifu Univ. (Japan)) | Utsumi, S.
The significance of muscarinic receptors in the feedback autoinhibition of acetylcholine output evoked by distention and exposure to external excess potassium was investigated in the isolated guinea-pig whole intestine and circular muscle preparation. From the effect of tetrodotoxin, it was concluded that about 40% of the output from the intestine is due to propagated activity in the plexus. The output of acetylcholine in the whole intestine in response to circumferential distention was enhanced by atropine (5-500nM), but depressed by muscarinic receptor agonist, oxotremorine (20mu-M). However, external excess potassium-induced acetylcholine output was only insignificantly increased by atropine. Acetylcholine output by circular muscle preparation was unaffected by atropine or oxotremorine. The results indicate that acetylcholine output from interneuronal cholinergic nerves is regulated by presynaptic inhibitory muscarinic receptors in the guinea-pig ileum
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