Glutamic acid decarboxylase mRNA in rat brain: regional distribution and effects of intrastriatal kainic acid.

Glutamic acid decarboxylase (GAD) mRNA was quantified in different regions of rat brain using an antisense RNA probe (ribo-probe) prepared from a cloned feline cDNA. In all brain regions studied a single band of GAD mRNA of approximately 3.7 kb was detected. The level of GAD mRNA was highest in the cerebellum, followed by the hypothalamus greater than thalamus greater than striatum greater than hippocampus greater than frontal cortex = parietal cortex greater than or equal to medulla = pons. Since GAD has been previously localized to intrinsic neurons of the striatum, we examined the effects of intrastriatal kainic acid administration on striatal GAD mRNA. The level of GAD mRNA in the kainic acid-lesioned striatum was reduced by 70-75% when compared to the contralateral (unlesioned) striatum. In contrast, the level of glutamine synthetase (an enzyme localized to glia) mRNA was increased approximately 290% in the kainic acid-lesioned striatum. There were no significant differences in GAD mRNA levels between the ipsilateral and contralateral cerebral cortices and hippocampi of rats injected with intrastriatal kainic acid.