Release of Curare-Like Agent from Healthy Muscle and Its Bearing on Myasthenia Gravis. *

Abstract

Summary and Conclusions

(1) The effect of serum collected after passive movements of limbs of cats with occluded circulation on the neuro-muscular transmission of the frog was compared to the effect of serum obtained from immobilized limbs with occluded circulation, and from limbs with occluded circulation after intermittent or continuous electrical stimulation of the motor nerve. (2) Serum collected from passively moved limbs depressed the neuro-muscular transmission of the frog, whereas serum collected from immobilized limbs and limbs after intermittent stimulation of the motor nerve did not modify the neuromuscular transmission. Serum collected from limbs after continuous stimulation of the motor nerve depressed the neuro-muscular transmission of the frog to a lesser extent. (3) The following postulate is offered: (a) that during performance of muscle work agents with curare-like effect are passed into the blood; (b) that in healthy subjects the effect of these substances is counteracted by sufficient amounts of stimulator substances or decomposition products thereof; (c) that in patients with myasthenia gravis the decrease of the synthesis of acetylcholine-like substances may manifest itself by the decrease of stimulator substances during the performance of work; and (d) that the lack of stimulator substances allows the usual agents with curare-like effect to manifest their presence during performance of work. The decreased release of acetylcholine-like substances a t the synapse by itself, the dominance of substances with apparent curare-like effect, and perhaps also other not yet identified processes may lead to the easy fatiguability observed in patients with myasthenia gravis.