Depression of Acetycholine Synthesis by Serum from Working Muscle. Healthy Subjects and Myasthenia Gravis Patients. ∗

Abstract

Summary

1. The effect of muscle work of healthy subjects and patients with myasthenia gravis on the ability of serum to modify acetylcholine synthesis in vitro was investigated. 2. Acetylcholine synthesis in mixtures of frog brain and serum from immobilized arm of healthy subjects was twice as much as in the absence of serum. 3. Acetylcholine synthesis in the presence of serum from working arm was 40% less than in the presence of serum from immobilized arm. 4. Acetylcholine synthesis in the presence of serum from the immobilized arm of patients with myasthenia gravis was less than in the presence of serum from the immobilized arm of healthy subjects. The more severe the myasthenia gravis, the less the acetylcholine synthesis. 5. Acetylcholine synthesis in the presence of serum from the working arm of patients with myasthenia gravis was 15 to 26% less than with serum of their own immobilized arm, but on the average 42 % less than the amount synthesized in the presence of serum from the immobilized arm of healthy subjects. 6. Muscle fatigue may be in part the result of the decrease of the local synthesis of an acetylcholine-like substance during prolonged muscle contractions. 7. Implications regarding the symptomatology of myasthenia gravis are presented.