PHYSIOLOGICAL AND IMMUNOCYTOCHEMICAL DETERMINATION OF THE NEUROTRANSMITTER AT CRICKET NEUROMUSCULAR-JUNCTIONS

An attempt was made to determine electrophysiologically and immunocyto chemically the neurotransmitter at neuromuscular junctions (NMJs) in c ricket abdominal muscles. One mM bath-applied L-glutamate reduced the amplitudes of large and small excitatory junctional potentials (I- and s-EJPs) reversibly by about 75% of the control on the average. It als o produced a slow, transient depolarization of about 10 mV. Joro spide r toxin, which is an antagonist of L-glutamate, depressed the amplitud es of I- and s-EJPs almost completely and irreversibly at 3.5 x 10(-6) M. By using the antibody to glutamate, glutamate-immunoreactive proce sses whose configuration resembled that of NMJs revealed by nickel sta ining were obtained. The present results strongly suggest that the neu rotransmitter at cricket NMJs is L-glutamate.