INHIBITORY POSTSYNAPTIC POTENTIALS IN GRASSHOPPER MUSCLE.

Hyperpolarizing inhibitory postsynaptic potentials have been discovered in fibers of the "jumping" muscle of the grasshopper. These potentials attenuate the depolarizing excitatory postsynaptic responses. They are enhanced during depolarization of the muscle fiber with applied current and are diminished and then reversed during hyperpolarization. The electrogenesisappears to be caused by chloride-activation. Gamma-aminobutyric acid activates the inhibitorysynaptic membrane and picrotoxin is an inactivator agent.