EFFECT OF GLYCEROL TREATMENT ON TRANSMITTER RELEASE AT THE FROG NEUROMUSCULAR-JUNCTION

Exposure of frog skeletal muscle to a Ringer solution made hyperosmoti c with glycerol, followed by return of the preparation to a normal Rin ger, results in an irreversible uncoupling of the mechanical activity of the muscle. This technique for preventing muscle contraction has of ten been used to study neuromuscular transmission under normal or high levels of release without interference from muscle contraction. Littl e was known, however, about the effects of glycerol treatment on the p rocess of transmitter release. In this paper we report the results of a study in which we examined the effects of glycerol treatment on tran smitter release during repetitive stimulation at the frog sartorius ne uromuscular junction. We found that glycerol treatment altered the sti mulation-induced changes in end-plate potential (EPP) amplitude normal ly observed during repetitive stimulation at this synapse. This effect , which increased progressively with time for up to 8 h following remo val of glycerol, could be accounted for by presynaptic changes in the amount of transmitter released.