Interactions between alcohol and nicotine on intracranial self-stimulation and locomotor activity in rats.

These studies were aimed at investigating interactions between alcohol and nicotine on operant behavior and on locomotor activity. Independent groups of rats with electrodes in the lateral hypothalamus were trained to lever press for intracranial self-stimulation (ICSS) on either a fixed-ratio 15 (FR 15), FR 30, fixed-interval 15-second (FI 15-s) or FI 30-s schedule of reinforcement. In the FI 15-s experiment, nicotine increased and alcohol decreased responding. This also happened in the FI 30-s experiment; however, when the two drugs were combined, an increase in lever pressing occurred which was greater than that produced by nicotine alone. Nicotine increased rates in the FR 15 schedule but, when combined with alcohol, did not reverse the decrease in rates produced by alcohol. In the FR 30 schedule, nicotine also increased response rates, but did not reverse the decrease produced by alcohol in this paradigm. A separate group of animals was tested in a locomotor activity apparatus following administration of nicotine, alcohol or their combination. Nicotine increased locomotor activity and alcohol depressed it. However, when 0.10 or 0.17 mg/kg nicotine was combined with 0.3 g/kg alcohol, an increase greater than that produced by nicotine alone occurred. We have found that alcohol and nicotine together can produce a potentiation of nicotine's stimulatory effects depending upon the dose and the requirements of the task.