EFFECT OF CONVULSANT ALLYLGLYCINE (2-AMINO-4-PENTENOIC ACID) ON ACTIVITY OF GLUTAMIC-ACID DECARBOXYLASE AND CONCENTRATION OF GABA IN DIFFERENT REGIONS OF GUINEA-PIG BRAIN

I.p. administration of allylglycine to guinea pigs resulted in convulsions approximately 3 h later. The concentration of GABA and the activity of GAD [glutamic acid decarboxylase, EC 4.1.1.15] were significantly reduced in 3 brain areas, i.e., the cochlear nucleus, inferior colliculus and cerebral cortex, with the smallest changes in the cortex. There were large in vitro regional variations in the extent of the allylglycine inhibition in brain areas from guinea pig, cat and rat, with those areas rich in GAD activity being least affected. Endogenous GAD activities in the brain regions were inversely correlated with the percentage allylglycine inhibition (P < 0.005). Other inhibitors of GAD activity, i.e,, NaCl, Zn2+ and thiosemicarbazide showed no such regional variation of inhibition. The regional differences in allylglycine inhibition reflected anomalies of the metabolism of the drug per se, and probably do not indicate regional differences in GABA turnover and metabolism.