Inescapable shock reduces [³H]Ro 5-4864 binding to "peripheral-type" benzodiazepine receptors in the rat

[³H]Ro 5-4864 binding to "peripheral-type" benzodiazepine receptors was examined in brain and peripheral tissues of rats subjected to inescapable tailshocks. Two hours after a session of 80 (five-second) inescapable tailshocks, a significant reduction in [³H]Ro 5-4864 (10 nM) binding was observed in membranes from kidney (31%), cerebral cortex (29%), heart (19%) and pituitary (17%) compared to tissues from naive animals. In contrast, inescapable shock did not effect [³H]Ro 5-4864 binding to hippocampal, lung, or adrenal membranes. Scatchard analyses of [³H]Ro 5-4864 binding to renal membranes demonstrated that this session of tailshock reduced the density (B_max) of "peripheral-type" benzodiazepine receptors without effecting the apparent affinity (K_d) of the radioligand for these sites. The effects of graded stress on [³H]Ro 5-4864 binding to cerebral cortex and kidney were investigated using 5, 20, or 80 (five-second) inescapable shocks. In cerebral cortical membranes, sessions of either 5 or 20 shocks did not affect, while 80 shocks reduced (29%) [³H]Ro 5-4864 (10 nM) binding. In renal membranes, 5 shocks significantly increased (35%), 80 shocks significantly decreased [³H]Ro 5-4864 (10 nM) binding (31%). These findings demonstrate that the density of "peripheral-type" benzodiazepine receptors in both peripheral tissues and the central nervous system can be rapidly modulated by stress.