Benzodiazepine effect of 125I-iomazenil-benzodiazepine receptor binding and serum corticosterone level in a rat model

To test the change in free or unoccupied benzodiazepine receptor (BZR) density in response to diazepam, we investigated 125I-iomazenil (125I-IMZ) binding and serum corticosterone levels in a rat model. Wistar male rats, which received psychological stress using a communication box for 5 days, were divided into two groups according to the amount of administered diazepam: no diazepam [D (0)] group and 10 mg/kg per day [D (10)] group of 12 rats each. The standardized uptake value (SUV) of 125I-IMZ of the D (10) group were significantly lower (P<.05) than those of the D (0) group in the frontal, parietal and temporal cortices, globus pallidus, hippocampus, amygdala and hypothalamus. The serum corticosterone level ratio in the D (10) group was significantly lower than that in the D (0) group (P<.05). From the change in serum corticosterone levels, diazepam attenuated the psychological stress produced by the physical stress to animals in adjacent compartments. From the reduced binding of 125I-IMZ, it is clear that diazepam competed with endogenous ligand for the free BZR sites, and the frontal, parietal and temporal cortices, globus pallidus, hippocampus, amygdala and hypothalamus are important areas in which 125I-IMZ binding is strongly affected by administration of diazepam.