Abstract

Treatment of rats for 10 days with Di-Syston, an organophosphorus cholinesterase inhibitor, produced subsensitivity of the ileum to carbachol, oxotremorine and furtrethonium. The same treatment caused an increased sensitivity of the ileuin to acetylcholine and butyrylcholine which was not unexpected since both of these substances are hydrolyzed by ileum cholinesterase. Subsensitivity did not develop to the action of potassium or to the action of methacholine, a result which suggests that subsensitivity may develop only to certain types of drugs.