The cerebral cortex of unstressed rats has a higher density of low affinity gamma-aminobutyric acid (GABA) receptors than that of stressed animals. Stress (handling or foot shock) produces a sudden decrease in the total number of low-affinity GABA receptors in the cerebral cortex of unstressed rats but leaves unchanged the density of GABA receptors in the cortex of stressed animals. The in vivo administration of Ro 15-1788 (30 mg/kg per os), a specific benzodiazepine receptor antagonist, completely prevents the effect of footshock on the low-affinity GABA receptors. The results suggest that (a) benzodiazepine recognition sites are involved in the action of stress on GABA receptors, and (b) stress may release an endogenous ligand for the benzodiazepine recognition site
