Nicotine enhances the learning and memory of aged rats

The cognitive performance of young adult (2-3-month-old) and aged (22-24 month-old) rats was characterized in one of three different behavioral tasks, and the ability of daily nicotine treatment to alleviate age-related learning and memory deficits was evaluated. Aged rats received an IP injection of either nicotine (0.2 mg/kg) or saline vehicle 15 min prior to daily testing; young control rats received saline vehicle injections. Compared to young controls, aged control rats were severely impaired in the acquisition of one-way active avoidance pole jumping over 12 days of testing. Nicotine pretreatment of similar aged rats markedly improved overall learning and the rate of learning compared to aged controls. In Lashley III maze performance, aged control rats made substantially more alternation errors than young controls; however, aged rats pretreated with nicotine made significantly fewer errors over the entire 20-day test period compared to aged controls. During 30 days of 17-arm radial maze testing, aged control animals were severely impaired in general learning and reference (long-term) memory, but only mildly impaired in working (short-term) memory. Nicotine pretreatment of similar aged rats induced a substantial enhancement in overall learning and reference memory, but did not affect working memory. These results indicate that chronic nicotine administration can improve the impaired learning/memory abilities of aged rats in several tasks, and suggest that stimulation of central nicotinic receptors may be of considerable therapeutic value to treat age-related memory impairment.