ACUTE NICOTINE INTERACTIONS WITH NICOTINIC AND MUSCARINIC ANTAGONISTS- WORKING AND REFERENCE MEMORY EFFECTS IN THE 16-ARM RADIAL MAZE

In the 8-arm radial maze and other tests, acute nicotine administratio n has been found to improve memory performance significantly, whereas acute administration of the nicotinic antagonist mecamylamine has been found to impair memory performance. However, questions remain concern ing the behavioral and pharmacological nature of acute nicotine effect s on memory. In the current studies, we examined acute nicotine effect s on working and reference memory in a 16-arm radial maze. In the firs t study, nicotine caused a significant improvement in working memory b ut not in reference memory. The muscarinic antagonist scopolamine caus ed significant deficits in working memory but not in reference memory. Nicotine did not significantly attenuate the scopolamine-induced defi cit. In the second study, with rats trained to near-perfect performanc e, a low dose of mecamylamine (1.25 mg/kg) caused a significant workin g memory impairment in the 16-arm maze. This deficit was significantly attenuated by concurrent acute administration of nicotine. These stud ies show that acute nicotine, like chronic nicotine, preferentially im proves working compared with reference memory in the radial-arm maze. Mecamylamine can impair working memory performance in the 16-arm maze at low doses which are less likely to have effects at N-methyl-D-aspar tate receptors. Nicotine can selectively reverse mecamylamine-induced deficits.