NICOTINE REINSTATEMENT OF NICOTINE SELF-ADMINISTRATION AFTER LONG-TERM EXTINCTION

The effect of non-contingent priming injections of nicotine on the rei nstatement of drug-seeking behaviour was studied in rats following the long-term extinction of nicotine self-administration. Male rats were trained to lever press for 0.03 mg/kg per infusion of intravenous nico tine. Nicotine maintained a robust self-administration behaviour (11.5 +/- 1.2, mean +/- SEM infusions/1-h session). When nicotine availabil ity was discontinued, and only a non-contingent saline infusion was pr esented to the experimental subjects at the beginning of each daily se ssion, responding for the drug-paired lever decreased to low values. A fter 4-13 sessions, responding extinguished. During this ''extinction' ' period, non-contingent priming infusions of nicotine 0.001, 0.003, 0 .01 or 0.03 mg/kg per infusion induced reinstatement of responding for the drug-paired lever. The increased responding, compared with the co rresponding previous day on saline, was observed at all four nicotine doses but was not statistically significant for the higher priming dos e (0.03 mg/kg per infusion). These preliminary results indicate that n icotine priming is able to induce reinstatement of drug-seeking behavi our in rats similarly to other reinforcing drugs. The present findings show analogies with similar phenomena described in ex-smokers and sup port the addictive role of nicotine in tobacco smoking.