BICUCULLINE ADMINISTERED INTO THE AMYGDALA AFTER TRAINING BLOCKS BENZODIAZEPINE-INDUCED AMNESIA

Male Sprague-Dawley rats were injected (i.p.) with either midazolam (M DZ, 2.0 mg/kg) or vehicle (1.0 ml/kg) 10 min before they were trained on a multiple-trial inhibitory avoidance task. Immediately following t he training, bicuculline methiodide (BMI; 2.0, 5.6, 56.0 or 197.0 pmol /0.5 mu l) or vehicle (0.5 mu l) was infused bilaterally into the amyg dala. On a 48 h retention test the performance of the MDZ-treated anim als was significantly poorer than that of controls. The retention of M DZ-treated animals given intra-amygdala injections of the lowest dose of BMI (2.0 pmol) was comparable to that of controls, whereas higher d oses of BMI impaired retention. The present results are consistent wit h other findings indicating that the amygdala mediates the amnestic ef fects of benzodiazepines on aversive learning. Furthermore, these data suggest that benzodiazepines impair memory by disrupting post-trainin g processes underlying memory consolidation. (C) 1997 Elsevier Science B.V.