Drug and Alcohol Dependence, 33 (1993) 225 - 234 Elsevier Scientific Publishers Ireland Ltd. 225 Effects of cocaine self-administration on ethanol, food and water intake in the rat Thomas J. Hudzik, W.D. Wessinger and D.E. McMillan Department of Pharmacology and Toxicology, University zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGF Arkansas for Medical zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR Sciences. 4.301 W. Markham St., Slot 611. Little Rock, AR 72205 (USA) (Accepted April 1, 1993) Because cocaine and ethanol are frequently abused in combination, the present study was performed to assess the behavioral consequences of concurrent access to both of these drugs. Rats trained to respond for food under a fixed-ratio 40 (FR 40) schedule of reinforcement during four, 30-min periods each day (every 6 h) were given free access to a 5% (w/v) ethanol solution and to water. Once a stable baseline of food, ethanol and water intake was established, intravenous cocaine was made available under a fixed-ratio 1 (FRl) schedule. After cocaine self-administration had been established for 10 days, the ethanol was removed from the chambers for 3 days. After the ethanol was returned to the chambers, saline was substituted for cocaine for 3 days. Following saline substitution, animals were given increased cocaine availability. Before cocaine was made available, rats consumed primarily the ethanol solution, averaging 31.7 ml of the 5% solution (4.2 g/kg ethanol), 10.2 ml of water and 148 food pellets/day. When cocaine (0.2 mg/kg per injection, iv.) was made available, rats self-administered an average of 40 - 85 injections per day. Self-administration of cocaine resulted in small decreases in ethanol and food intake, as well as some changes in the pattern of ethanol intake. However, removing the ethanol from the chambers had no effect upon food and cocaine intake. Substitution of saline for the cocaine altered the pattern, but not the amount of ethanol intake. There was a trend toward increased ethanol intake during the study, which may have been related to repeated cycles of cocaine availability. Key words: cocaine self-administration; ethanol intake; food intake; water intake; rats Introduction It is a rarity that an illicit drug user will abuse a single substance, and as such, it becomes likely that two or more drugs will be concurrently used (Kreek, 1987). However, the questions of how the availability and intake of one drug can affect the pattern and maintenance of intake of a sec- ond drug has not been extensively studied. According to a recent national survey the drug most frequently reported to be combined with cocaine was ethanol (Johnson et al., 1985; Grant and Hartford, 1990), which is possibly related to the high availability of both drugs. CorrespMe to: T.J. Hudzik, Division of Biology, Fisons Pharmaceuticals, P.O. Box 1710, Rochester, NY 14603, USA. Also possibly related to the concurrent abuse of ethanol with cocaine are observations that the presence of ethanol appears to produce an enhancement of the mood-elevating effects of cocaine (Perez-Reyes and Jeffcoat, 1992). Con- current abuse of cocaine and ethanol has been associated with higher morbidity and mortality than is seen with cocaine alone (Hearn et al., 1991), perhaps due to the enhancement of the cardiovascular effects of cocaine when concur- rently administered with ethanol (Foltin and Fischman, 1989; Perez-Reyes and Jeffcoat, 1992). One additional factor in the co-abuse of ethanol and cocaine is that ethylcocaine occurs as an active cocaine metabolite in individuals concurrently using ethanol (Hearn et al., 1991; Jatlow et al., 1991; Perez-Reyes and Jeffcoat, 1992). Although metabolic and physiological in- 0376.8716/93/$06.00 0 1993 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland