Development of homospecific activity of GABA-transaminase in the mouse cerebral cortex and cerebellum and in neurons cultured from these brain areas.

The homospecific activity of GABA-transaminase (EC 2.6.1.19; GABA-T) in brain or neurons was determined as a function of development in vivo or in culture by measuring the enzyme activity together with the relative amount of GABA-T apoenzyme by the aid of a monospecific anti-GABA-T antibody. It was observed that both in cerebral cortex and cerebellum in vivo and in neurons cultured from these brain regions the homospecific activity of GABA-T changed during development. By incubation of tissue extracts with similar extracts in which GABA-T activity had been selectively and irreversibly destroyed with gamma-vinyl GABA (Vigabatrin) it was established that this change in homospecific activity was at least partly due to the presence of an endogenous activator of GABA-T. The results point towards a rather complex endogenous regulation of GABA-T during development in vivo and in vitro.