SOME EFFECTS OF ATROPINE ON SMOOTH MUSCLE.

Contractions of the nerve-free smooth muscle of the chick amnion, either spontaneous or in response to electrical or mechanical stimuli, are potentiated by high conentrations (10(-5) g/ml.) of atropine sulphate. In addition hyoscine, homatropine, lachesine, propantheline bromide and atropine N-methyl and atropine N-butyl salts potentiate spontaneous activity in the amnion. The effects of atropine do not appear to depend on inhibition of cholinesterase; on labilization, stabilization or depolarization of the muscle cell membrane; or on an increase in metabolism. It is suggested that the effects are the result of blockade of the muscarinic acetylcholine receptors. The way in which this may facilitate the conducted response is discussed.