GABA and Benzodiazepine Receptors in the Gerbil Brain after Transient Ischemia: Demonstration by Quantitative Receptor Autoradiography

Quantitative receptor autoradiography was used to measure the binding of γ-aminobutyric acid (GABA) and benzodiazepine receptors after ischemia by means of transient occlusion of bilateral common carotid arteries in the gerbil. [³H]Muscimol was used to label the GABA_A receptors and [³H]funitrazepam to label central type benzodiazepine receptors. In the superolateral convexities of the frontal cortices, [³H]muscimol binding was increased in 60% of the animals killed 3 days after ischemia, and decreased in 67% of the animals killed 27 days after ischemia. Twenty-seven days after ischemia, [³H]funitrazepam binding in the substantia nigra pars reticulata increased to 252% of the control, though the increase in [³H]muscimol binding was not significant. In the dorsolateral region of the caudate putamen, marked neuronal necrosis and depletion of both [³H]muscimol and [³H]funitrazepam binding sites were observed 27 days after ischemia, the ventromedial region being left intact. In spite of the depletion of pyramidal cells in the CA1 region of the hippocampus, both [³H]muscimol and [³H]funitrazepam binding sites were preserved 27 days after ischemia. Since our previous study revealed that adenosine A₁ binding sites were depleted in the CA1 subfield of the hippocampus after ischemia correlating with neuronal damage, GABA_A and benzodiazepine receptors may not be distributed predominantly on the pyramidal cells in the CA1 region.