Lesioning of the rat basal forebrain leads to memory impairments in passive and active avoidance tasks.

Effects of the bilateral electrolytic lesioning of the basal forebrain (BF), including the ventral globus pallidus, on passive or active avoidance tasks, were studied in male Wistar rats. A severe deficit in acquisition of passive avoidance response was produced by the lesioning in the posterior level of BF. The retention of the passive avoidance response was markedly disrupted with post-training lesioning. Time-dependent but only slight recovery from the memory impairments was observed in the passive avoidance task given 4, 8 or 16 weeks after BF lesions. The acquisition of active avoidance response using a two-way shuttle box was also disturbed by BF lesioning. Retention of active avoidance response was clearly impaired by post-training lesions of the BF. The BF lesioned rats gradually acquired the passive avoidance performance when trained repeatedly at 24- or 48-h intervals, by giving a foot shock in case of avoidance failure. Extinction of the acquired passive avoidance response rapidly occurred in the BF lesioned rats. Furthermore, neurotoxic lesions of BF with kainic acid produced a significant impairment in acquisition of passive avoidance response. These results suggest that bilateral BF lesions impair the acquisition and retention of passive or active avoidance response, and that these impaired rats may be useful as an experimental model for Alzheimer's disease and senile dementia.