Elevated immunoreactivity for glutamic acid decarboxylase in the rat cerebral cortex following transient middle cerebral artery occlusion.

We investigated the expression of glutamic acid decarboxylase (molecular weight 67,000; GAD67) immunohistochemically in the rat cerebral cortex following transient middle cerebral artery occlusion (MCAO) capable of producing slowly progressive neuronal damage. An increase in GAD67 immunoreactivity was observed in the cerebral cortex ipsilateral to the ischemic insult, most prominent in lamina IV, 3 to 14 days after MCAO. At this stage, light microscopy showed GAD67-positive puncta to be larger and more strongly immunoreactive in the ipsilateral cortex than those in the contralateral side. The elevated expression of GAD67 in the insulted cortex may reflect part of the adaptive functional changes in GABA transmission with slowly progressive cortical ischemic damage.