Effects of repeated administration of (-)-nicotine on AF64A-induced learning and memory impairment in rats

It has been reported that pretreatment with (-)-nicotine prevents glutamate- and amyloid beta protein (Aβ)-induced cytotoxicity in vitro. However, few studies on the neuroprotective effects of (-)-nicotine in vivo have been reported. We examined whether repeated administration of (-)-nicotine exhibits neuroprotective effects in AF64A-treated rats. (-)-Nicotine (0.1 and 0.2mg/kg, s.c.) was administered once a day for 28 days. On day 14, AF64A (2.5nmol/side) was injected bilaterally into the hippocampus. Intrahippocampal injection of AF64A showed severe impairment of learning and memory in rats in the water maze and passive avoidance tests. Repeated administration of (-)-nicotine (0.1 and 0.2mg/kg, s.c.) did not reverse the impairment of memory induced by AF64A in the water maze test. Interestingly, the (-)-nicotine (0.1 and 0.2mg/kg, s.c.)-treated group showed weak impairment of learning and memory after AF64A treatment compared to the (AF64A + saline)-treated group in the passive avoidance test. These results suggested that (-)-nicotine may have neuroprotective effects against the neurotoxicity induced by AF64A.