PHARMACOLOGICAL CONTRIBUTIONS TO THE PROBLEM OF THE AUTONOMIC CONTROL OF SKELETAL MUSCLE TONUS

¹ From the Department of Laboratories, The Mount Sinai Hospital, New York

1. The drugs acting on the autonomic system, when locally administered to intact guinea pigs, display a perceptible action upon the tonus of the abdominal wall muscle.

2. Adrenaline and atropine induce a decrease in tonus, manifested by the pseudohernia phenomenon.

3. Ergotamine and acetylcholine (as well as pilocarpine), under suitable conditions, produce the opposite effect; ergotamine prevents the adrenaline pseudohernia, the parasympathomimetic drugs cause an increased tonus demonstrable by the expedient of abdominal insufflation. Ergotamine also displays its action when systemically administered.

4. In an experimental analysis, the fundamental difference between the adrenaline effect and the proprioceptive pseudohernia effect of local anesthetics is brought forward and strong support is given to the conclusion that the locus of attack of adrenaline are those sympathetic nerve endings concerned with direct inhibitory stimulation of the tonus function.

5. The relations of these observations to the problem of an autonomic control of the skeletal muscle tonus are discussed. The abdominal wall muscle of the guinea pig is revealed as a striped muscle in which the autonomic control of tonus is provided by parasympathetic augmentation and sympathetic inhibition,—a type which is closely related to that of many smooth muscle organs.