CCK-8 modulates GABA-stimulated [3H]-flunitrazepam binding in vitro

In membranes from rat cerebral cortex, cholecystokinin-8 (CCK-8) did not modulate basal [(3)H]-flunitrazepam binding at either 4 degrees C or 37 degrees C. At a concentration of 10(-6) M, CCK(-8) significantly decreased gamma-amino-butyric acid (GABA)-stimulated (10(-6) M) [(3)H]-flunitrazepam binding at 37 degrees C. Scatchard analyses suggest that the decreased GABA-stimulated binding might be due to a decrease in the affinity of benzodiazepine receptors rather than to a decrease of number of binding sites. The observed modulation of benzodiazepine receptors by CCK-8 in vitro might explain some of the functional interactions between CCK and benzodiazepine systems.