Individual differences in rat locomotor activity are diminished by nicotine through stimulation of central nicotinic acetylcholine receptors

An increasing body of research has focused on isolating factors that predic t or alter individual differences in the behavioral and neural processes me diating the effects of abused drugs. Within this framework, the current rep ort assessed individual differences and the locomotor effect of nicotine. R ats were screened for activity induced by a novel environment. Rats, which were more active to initial environment exposure, remained more active even after seven additional 30-min exposures to the same environment. Treatment with nicotine-di-D tartrate (1 mg/kg, sc) disrupted this effect. This nico tine disruption of individual differences occurred whether nicotine suppres sed locomotor activity (initial administration) or stimulated locomotor act ivity (seventh and eighth administration). Mecamylamine (1 mg/kg), but not hexamethonium (10 mg/kg), completely blocked the suppressant and stimulant effects of nicotine. Further, mecamylamine restored the nicotine-induced di sruption of individual differences; hexamethonium had no effect. This data pattern suggests that the disruptive effects of acute and chronic nicotine on individual differences were mediated by neural nicotinic acetylcholine ( nACh) receptors. (C) 2001 Elsevier Science Inc. All rights reserved.