The influence of cholinoceptor activity on the mitotic rate in the crypts of Lieberkühn in rat jejunum.

1. The influence of cholinoceptor stimulation and cholinoceptor blockade on the mitotic rate in epithelial cells lining the crypts of Lieberkühn in rat jejunum was studied. 2. Cholinoceptor stimulation, either by injection of carbachol or by inhibition of acetylcholinesterase enzymes resulted in an increase in the mitotic rate. This increase in mitotic rate was blocked by tubocurarine, but not by atropine or hexamethonium. Atropine by itself increased the mitotic rate whereas tubocurarine alone or hexamethonium along decreased the mitotic rate. 3. The influence of atropine on crypt cell proliferation appears to involve an adrenergic mechanism since it is blocked by phentolamine.