THE EFFECT OF THE CONVULSANT 3‐MERCAPTOPROPIONIC ACID ON ENZYMES OF THE γ‐AMINO‐BUTYRATE SYSTEM IN THE RAT CEREBRAL CORTEX

Abstract —The activities of GABA enzymes in rat cerebral cortex were studied after the administration of the convulsant, 3‐mercaptopropionic acid (MP). We found that MP markedly inhibited glutamate decarboxylase (EC 4.1.1.15) and activated GABA‐aminotransferase (EC 2.6.1.c). The level of GABA appeared to be decreased during convulsions but thereafter returned to normal. The study of the subcellular distribution of GABA enzymes after the administration of MP indicated that the glutamate decarboxylase present in the nerve endings was not affected, while GABA aminotransferase in the mitochondria was activated to a similar extent to that observed in the original homogenate. These results together with the recovery of glutamate decarboxylase activity in cortical homogenates by dialysis suggested a reversible type of inhibition, whereas the effect on GABA‐aminotransferase seemed to be more permanent.