Abstract
RATIONALE: Establishing a behavioral model for the effect of social environment on nicotine intake in rodents facilitates the investigation of molecular mechanisms critical for the interaction between social environment and cigarette smoking. OBJECTIVES: Our main objective was to test the hypothesis that nicotine is the primary reinforcer in the socially acquired nicotine intravenous self-administration (IVSA) model by using an aversive flavor cue. METHODS: Adolescent female rats were placed in operant conditioning chambers equipped with two lickometers. Operant licking triggered concurrent deliveries of a flavor (i.e., taste and odor) cue containing either quinine or saccharin and an i.v. infusion (30 μg/kg nicotine or saline). An audiovisual cue was provided for some groups of rats. A second rat that did not receive nicotine was placed in the operant conditioning chambers to provide either a neutral or an inducing (i.e., by consuming the flavored solution) social environment. These two rats were separated by a divider that allowed orofacial interactions. RESULTS: Rats acquired stable nicotine IVSA with either the aversive or the appetitive flavor cue in the inducing social environment, and obtained similar amounts of infusions. The neutral social environment did not support nicotine IVSA with either cue. The audiovisual cue per se did not support nicotine IVSA but enhanced nicotine intake. Nicotine increased the number of concurrent nose pokes by the two rats into the center divider, a measure of social interaction. CONCLUSIONS: Despite its aversive effects, nicotine is the primary reinforcer for the operant responses in the socially acquired nicotine IVSA model.