MIDAZOLAM ADMINISTERED TO RATS INDUCES ANTEROGRADE AMNESIA FOR CHANGES IN REWARD MAGNITUDE

P. Crespi (1942) showed that rats trained to run an alley for a large food reward slowed down when shifted to a small reward. This effect is usually interpreted as an aversive emotional response to reward reduc tion (A. Amsel, 1958). Benzodiazepines attenuate the behavioral effect s of reward reduction (cf. C. F. Flaherty, 1990), but the emphasis has been on their anxiolytic, not memory-impairing, effects. Researchers trained rats (175-200 g) to run an alley for food until asymptote was reached. Reward magnitude was then either decreased (Experiment 1) or increased (Experiment 2). The benzodiazepine midazolam (1 mg/kg ip), i njected immediately prior to a decrease or increase in reward magnitud e, impaired the later retention of both changes in a manner consistent with anterograde amnesia. The findings suggest that the memory-impair ing effects of benzodiazepines may, at least in part, influence the re sponse to reward reduction.