Nicotine enhances latent inhibition and ameliorates ethanol-induced deficits in latent inhibition

Alcohol and nicotine are drugs of abuse that are used frequently together. One possible explanation for this co-administration is that nicotine prevents or lessens alcohol-associated impairments. The present study examined the dose-dependent effects of acute administration of nicotine, alcohol, or alcohol plus nicotine on latent inhibition as measured by lick suppression in C57BL/6 mice. Alterations in a lick suppression ratio were measured by assessing the effects of 10 pre-exposures to an auditory conditioned stimulus (CS) on formation of subsequent CS-shock unconditioned stimulus (US) associations. Mice pre-exposed to the CS were expected to develop a weaker CS-US association. Nicotine administered prior to pre-exposure to the CS produced increased suppression ratios, ethanol given prior to pre-exposure to the CS decreased suppression ratios, and nicotine reversed the effects of ethanol when the two drugs were co-administered. These opposing actions of nicotine and ethanol may have relevance to the high incidence of smoking and drinking in humans.