The effect of nicotine on ethanol self-administration

The co-use of alcohol and nicotine is positively correlated in man, with people who drink alcohol having an increased probability of smoking and vice versa. Although alcohol and nicotine are one of the most common combinations of drugs abused by man, little is known why the co-use of these two drugs is seen. Previous animal studies have demonstrated that central nervous system actions of nicotine affect ethanol consumption in rats, suggesting that a pharmacological interaction is occurring between these two drugs. Experiment 1 examined the effect of daily experimenter-delivered nicotine on ethanol self-administration using an operant sipper model that separates appetitive (seeking) and consummatory (drinking) responding. Due to studies reporting a difference in central nervous system response to drugs of abuse based on contingency of delivery, experiments 2 (oral nicotine self-administration) and 3 (intravenous nicotine self-administration) examined the effect of self-administered nicotine on ethanol self-administration when the drugs were available in two separate sessions. The effect of availability of both nicotine (i.v.) and ethanol during the same operant session was examined in experiment 4.; The results from these studies suggest that although rats co-use nicotine and ethanol, both experimenter- and self-administered nicotine decrease the amount of ethanol consumed. Experiments 1 and 3 suggest that the contingency of nicotine delivery had no differential effect on subsequent ethanol self-administration. Nicotine administration preceding ethanol self-administration appeared to shift satiety for ethanol to the left, decreasing the amount of ethanol consumed. When the substances were co-available (experiment 4), and the rat determined the order of administration of the two drugs, nicotine may have been acting as an alternative reinforcer to ethanol decreasing the amount of ethanol that was consumed. Although the amount of ethanol consumed was decreased from baseline during co-available sessions, the rats administered both nicotine and ethanol during these sessions. Responding for ethanol was decreased following the high dose of experimenter-delivered nicotine and self-administered nicotine when it immediately preceded the ethanol session, these effects were most likely due to decreased locomotor activity in experiment 1 and satiety in experiment 3.