GLUTAMATE DECARBOXYLASE ACTIVITY IN RAT POSTERIOR PITUITARY, PINEAL-GLAND, DORSAL ROOT GANGLION AND SUPERIOR CERVICAL GANGLION

The possible existence of glutamate decarboxylase (EC 4.1.1.15; GAD) was investigated in the various non-cerebral tissues, in which GABA [.alpha.-aminobutyric acid] metabolism seems to be restricted to the glial or satelite cell elements. GAGA synthesis was compared in these tissues. In the cerebral cortex and the posterior pituitary apparent GAD activities measured by the 2 different procedures were very similar. In the pineal gland the apparent GAD activity measured by 14CO2 evolution was consideratly higher than that measured by GABA production. The apparent GAD activity in the cerebral cortex and posterior pituitary was significantly decreased in the presence of aminooxyacetic acid (AOAA) (1 mM) when measured by 14CO2 production, and even more markedly inhibited by AOAA when measured by GABA production. The pineal gland, sensory ganglia and sympathetic ganglia however, showed significant increases in 14CO2 evolution in the presence of AOAA. The use of AOAA and Cl--induced stimulation of 14CO2 evolution are not reliable criteria by which to differentiate between different forms of GAD in various non-cerebral tissues.