| Abstract: | Abstract— The activity of glutamate decarboxylase in rat striatal slices was estimated following preincubation in either a non-depolarizing medium or in a depolarizing medium. GAD activity was significantly increased following preincubation in normal Krebs-Ringer-phosphate medium as compared to activity in slices which were not preincubated. GAD activity in slices which were depolarized in high potassium Krebs-Ringer-phosphate medium was further increased when compared to activity in slices which were preincubated in normal medium. The depolarization-induced increase in GAD activity was graded in response to the time of depolarization, and both the increase following preincubation in normal medium and the increase following preincubation in high potassium displayed a relative requirement for calcium. In addition, net GABA formation from endogenous glutamate was increased in slices preincubated in high potassium medium as compared to net GABA formation from endogenous glutamate in slices preincubated in non-depolarizing medium. In support of the use of 14C]CO2 trapping as an estimate of GAD activity in slices, preincubation of slices in the presence of the GAD inhibitor glutamic acid γ-hydrazide caused a concentration-related inhibition of 14C]CO2 evolution. |
