Chronic infusion of nicotine can increase operant self-administration of alcohol

Effects of nicotine, administered by continuous infusion via osmotic minipu mps, were studied on the operant self-administration of alcohol by rats, us ing a variable interval (15 s) schedule, and measuring the acquisition, mai ntenance, extinction and reinstatement of responding for alcohol. Doses of nicotine of 0.25, 1.25 and 7.5 mg/kg/24 h had no significant effects on the maintenance of responding for alcohol, but 5 mg/kg/24 h nicotine resulted in a significant increase in responding on the lever delivering the reward when water was substituted for the alcohol. indicating delayed extinction o f responding. During infusion of 2.5 mg/kg/24 h nicotine, responding was si gnificantly greater over the "sucrose-fading" training sessions, during acq uisition of responding, when mixtures of alcohol and sucrose were provided as reward. When minipumps infusing 2.5 mg/kg/24 h nicotine were implanted a fter the alcohol responding had been acquired, the responding for alcohol i ncrease during the first week of nicotine infusion, but corresponding nicot ine infusion doses of 0.25, 1.25 and 7.5 had no significant effects. The re sults indicate that nicotine can increase operant responding for alcohol an d this is crucially dependent on the dose of nicotine and the time of testi ng. The results have implications for the frequently encountered dependence on the combination of alcohol and nicotine. (C) 2001 Elsevier Science Ltd. All rights reserved.