Facilitation of human tobacco self-administration by ethanol: a behavioral analysis.
The effect of ethanol on the cigarette smoking of alcoholic subjects was studied in a residential laboratory. During daily 6-hr sessions, cigarettes were obtained either by request to the ward staff or by operation of a lever (fixed-ratio 5 or 10). In a mixed sequence across days, sessions involved ingestion of either vehicle (orange juice or vehicle plus ethanol (133.7 g). During ethanol sessions, the rate of cigarette smoking increased from 26% to 117% of vehicle levels. A series of control studies eliminated a number of potential behavorial mechanisms for the observed effect and indicated that the ethanol-induced increase in cigarette smoking occurred under a variety of experimental conditions: (1) when smoking could not occur concurrently with ethanol or vehicle consumption; (2) when subjects were not allowed to socialize; (3) when ingestion of ethanol or vehicle was scheduled for a number of consecutive days; (4) when various doses of ethanol were administered under blind conditions. In control experiments, weighing unsmoked tobacco and counting the number of puffs per cigarette indicated the effect was not due to smoking less of each cigarette. The effect was not limited to the experimental sessions alone, since total daily smoking was higher on ethanol days than vehicle days.