The effect of chronic diazepam treatment on discrimination performance and 3H-flunitrazepam binding in the brains of shocked and nonshocked rats

The purpose of the present study was: (1) to investigate the effects of unavoidable shock on an appetitively motivated discrimination task; (2) to evaluate the effect of chronic diazepam treatment on the performance of a previously learned discrimination task in shocked and nonshocked animals; (3) to measure the binding of 3H-flunitrazepam (an analogue of diazepam) to selected brain regions of chronically diazepam-treated shocked and nonshocked rats, in comparison to saline-treated controls. Results indicated that unavoidable shock significantly interfered with the learning of a new, nonshock-related discrimination task. The effect of chronic diazepam treatment on the performance depended on the previous experience of the animal; chronic diazepam treatment significantly improved the maze performance of shocked animals. On the other hand, chronic diazepam treatment in the nonshocked animals tended to interfere with the performance of the discrimination task. Neurochemical data showed significant reduction in 3H-flunitrazepam binding to diazepam receptors in membranes from the brains of a nonshocked diazepam-treated (CD) group in comparison to a nonshocked saline-treated (CS) group. In contrast, the unavoidable shock-treated diazepam group (SD) showed opposite effects, the binding of 3H-flunitrazepam increasing significantly. A significant increase in the maximal binding sites in the frontal cortex from shocked rats treated with diazepam, compared to the nonshocked diazepam-treated rats, was detected by Scatchard analysis.