Self-Administration By Female Rats Of Low Doses Of Nicotine Alone Vs. Nicotine In Tobacco Smoke Extract

Background: Nicotine has reinforcing effects, but there are thousands of other compounds in tobacco, some of which might interact with nicotine reinforcement. Aims: This rat study was conducted to determine if nicotine self-administration is altered by co-administration of the complex mixture of compounds in tobacco smoke extract (TSE). Methods: Female Sprague-Dawley rats were tested for self-administration of low doses of nicotine (3 or 10 mu g/kg/ infusion) at three different rates of reinforcement (FR1, FR3 and FR5) over three weeks either alone or together with the complex mixture of tobacco smoke extract (TSE). Results: Rats self-administering 3 mu g/kg/infusion of nicotine alone showed a rapid initiation on an FR1 schedule, but declined with FR5. Rats self-administering nicotine in TSE acquired self-administration more slowly, but increased responding over the course of the study. With 10 mu g/kg/infusion rats self-administered significantly more nicotine alone than rats self-administering the same nicotine dose in TSE. Rats self-administering nicotine alone took significantly more infusions with the 10 than the 3 mu g/kg/infusion dose, whereas rats selfadministering nicotine in TSE did not. Nicotine in TSE led to a significantly greater locomotor hyperactivity at a dose of 0.1 mg/kg compared to rats that received nicotine alone. Rats self-administering nicotine alone had significantly more responding on the active vs. inactive lever, but rats self-administering the same nicotine doses in TSE did not. Conclusions: Self-administration of nicotine in a purer form appears to be more clearly discriminated and doserelated than nicotine self-administered in the complex mixture of TSE.