Muscarinic acetylcholine receptors of the small intestine and pancreas of the rat: distribution and the effect of vagotomy.

1. The distribution of muscarinic cholinergic receptors (mAChR), detected by atropine-inhibitable binding of [3H] quinuclidinyl benzilate, was examined in membrane fractions of pancreas, small intestinal muscle, mucosa, villi and crypts of sham-operated and vagotomized rats. 2. Specific (atropine inhibitable) [3H] quinuclidinyl benzilate binding was greater to the ileal mucosa than to jejunal mucosa or to duodenal mucosa, but binding crypt and villus fractions was not significantly different. This distribution of specific [3H] quinuclidinyl benzilate binding suggests that cholinergic mucosal innervation is more important in the ileum than the jejunum. 3. Vagotomy produced a decrease in the amount of specific [3H] quinuclidinyl benzilate binding to duodenal mucosa only, suggesting that parasympathetic denervation of the small intestine does not cause mucosal hypersensitivity to acetylcholine by an increase in mAChR.