High extracellular GABA levels in hippocampus--as a mechanism of neuronal protection in cerebral ischemia in adrenalectomized gerbils.

Adrenalectomy protects the brain from delayed neuronal damage that occurs following transient forebrain ischemia in gerbils. Gamma-amino butyric acid (GABA) and GABA-mimetic drugs also have a neuro-protective effect. In this study we estimated the extracellular glutamate and GABA levels in the hippocampus during transient forebrain ischemia in adrenelectomized gerbils (n = 8) compared to controls (n = 6). Duration of ischemia was 10 min, and glutamate and GABA levels were measured with in vivo microdialysis. Microdialysis was started 2 h after the placement of a probe (to stabilise baseline) and samples were collected at 10-min intervals. The pattern of glutamate release did not show any difference between adrenelectomized animals and controls. Adrenelectomized animals showed marked increase in GABA levels during ischemia and upto 30 min after ischemia (P = 0.0287, 2-way ANOVA for repeated measurements). The enhanced GABA release may be one of the possible mechanisms of neuronal protection against ischemia in adrenelectomized gerbils.