.GAMMA.-Aminobutyric acid metabolism in subcellular particles of mouse brain and its relationship to convulsions.

: The in vivo effects of convulsant drugs (hydrazine and penicillamine) on the metabolism of gamma-aminobutyric acid (GABA) in subcellular fractions of mouse brain were studied. Both substances inhibited the activity of glutamic acid decarboxylase [EC 4.1.1.15] (GAD) in the synaptosomal fraction (nerve ending particles) and reduced the concentration of GABA in the same fraction at the onset of convulsions, though changes in the total GABA concentration in the brain did not correlate with the onset of convulsions. Therefore, it is suggested that the concomitant decrease of GAD activity and GABA concentration in the nerve endings, independently of the total GABA concentration, is probably an important factor in the onset of some kinds of convulsions.