EFFECT OF AGING ON THE SPATIAL-LEARNING DEFICIT PRODUCED BY DIAZEPAM IN RATS

1. After pretraining in an undrugged state, young (6 months) and aged (18 - 24 months) rats were trained on a spatial learning-set task afte r receiving one of four doses of diazepam (1, 2, 3 or 5 mg/kg) or the drug vehicle. The effects of 5 mg/kg of diazepam were also assessed on the spatial learning-set task one full hour after injection (delay co ndition) as well as on the visible platform task. 2. During pretrainin g (undrugged), aged rats demonstrated a transient impairment on the vi sible platform task but subsequently did not differ significantly from young rats on the submerged platform task. On the spatial learning-se t task, aged rats performed as well as young rats under control condit ions and diazepam produced a comparable dose-dependent impairment of s patial learning. However, when the 1 hr delay was interposed between d iazepam administration and maze testing, only aged rats exhibited a sp atial learning impairment. Diazepam did not impair performance on the visible platform task in either young or aged rats. 3. These results i ndicate that although the amnesic effect of diazepam is not initially greater in aged rats, it persists for longer periods.