THE EFFECTS OF GLUTAMATE AND GABA (GAMMA-AMINO-BUTYRIC-ACID) ON SPONTANEOUS ACETYLCHOLINE-RELEASE AT THE NEUROMUSCULAR-JUNCTION IN XENOPUS-LAEVIS EMBRYO CELL-CULTURES

The miniature endplate currents (MEPC's) were recorded at the neuromus cular junction of Xenopus laevis embryo neuron-muscle co-cultured cell s. These MEPC's were due to the spontaneous release of acetylcholine f rom the nerve terminal. After perfusion with glutamate (10 mumol/L), b oth frequency and amplitude of the MEPC's increased. After washing awa y of glutamate, this effect persisted. We named this phenomena ''Long- Term Facilitation''. GABA (20 mumol/L) on the other hand had an inhibi tory effect on both frequency and amplitude of the MEPC's. After washi ng away of GABA, the MEPC frequency and amplitude increased. We named this effect ''Post-Potentiation''. Local perfusion experiments further more indicated that the effect of glutamate was restricted to the neur omuscular junction, the effect of GABA was restricted to the soma.