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RESEARCH PRODUCT

Muscarinic Modulation of Acetylcholine Release from the Myenteric Plexus of the Guinea Pig Small Intestine

subject

description

The concept of a local feedback regulation of neurotransmitter release has been most intensively studied in the adrenergic system (See Ref. 13 for review). The feedback hypothesis of noradrenaline release is based on the findings that α-adrenolytic drugs enhance, and α-adrenoceptor agonists reduce neuronal noradrenaline release. Relatively few systematic studies have been made on the influence of cholinolytic and cholinomimetic drugs on the release of ACh. Szerb and Somogyi (14) reported that the potent muscarinic agonist oxotremorine inhibited ACh output from cerebral cortical slices. Further, the muscarinic antagonists atropine and hyoscine have been found to facilitate the release of ACh from brain tissue in vivo (See Ref. 6 for references) and in vitro (2, 12). These findings led to the hypothesis that there is local regulation of ACh release from central cholinergic neurons via a negative feedback mechanism (12). The aim of the present work was to investigate whether the ACh output from the myenteric plexus of the guinea pig small intestine can also be modulated by atropine and muscarinic drugs.