The action of atropin,quinin,quinidin,and Ouabain on the fibrillation of the skeletal muscles.

Abstract

The fibrillary contractions of the skeletal muscles of the cat, following the systemic administration of physostigmin, were studied on thirty-three animals. Tracings of the fascicular movements of the pectoralis major muscle were analyzed, and changes in the action current of the pectoralis major, and of the adductor muscles of the hind leg were recorded, according to the method of Forbes and Thacher. 1

Evidence was presented in a previous communication 2 that the quantitative antagonism between physostigmin and atropin varies in different structures of the body. The antagonism of atropin is complete in the secretory system. It is of interest that atropin sulphate in intravenous doses of 2.5 to 5.0 mg. per kilogram of body weight, prevents or abolishes fibrillation of the skeletal muscles, when the latter is induced by intravenous injection of 0.3 to 0.5 mg. per kilogram of body weight of physostigmin salicylate. These produce marked generalized fibrillation in control animals. Massive doses of atropin do not prevent fibrillation induced by larger doses of physostigmin.

In the case of the skeletal muscles we are dealing, therefore, with a double antagonism, which, above a certain ratio, is cornplete in favor of the action of physostigmin. The experiments demonstrate a simultaneous drug antagonism with reversed results in different structures of the same animal.

The experiments with atropin suggest that the skeletal muscles contain certain nerve structures, which are parasympathetic in their pharmacodogical behavior. (Similar observations on the skeletal muscles of man were made recently by Weiss and Kennedy 3 ) Atropin prevents generalized convulsions due to physostigmin.

Quinin and quinidin prevent or suppress fibrillation induced by physostigmin, the muscular effect of which is not prevented by atropin. The minimal dose of quinidin is smaller than that of quinin, but they are equality effective when the activity is expressed in percentage of the fatal dose.