Caffeine promotes ethanol drinking in rats - Examination using a limited-access free choice paradigm

There is growing evidence that caffeine may alter the pattern of intake of a variety of drugs. The present study was designed to assess the effect of caffeine pretreatment on voluntary ethanol consumption. The first experimen t examined the effect of caffeine on the acquisition of ethanol intake in a limited-access-choice procedure in which water and ethanol were presented concurrently. Male Wistar rats, exposed to food and water ad lib, were pres ented with a daily 1-h choice session between water and progressively incre asing concentrations of ethanol (2-10%). Each ethanol concentration was mad e available for 4-6 days for a total of 20 days of access to ethanol. Intra peritoneal injections of caffeine (5 or 10 mg/kg) or saline were administer ed to the rats 30 min prior to each choice session. Caffeine produced a dos e-related facilitation in ethanol drinking whereby the lower caffeine dose produced enhancement in ethanol drinking. The second experiment examined th e effect of caffeine on the maintenance of established ethanol consumption. Male Wistar rats, initially acclimatized to increasing concentrations of e thanol (2%-10), were presented with an additional 18 ethanol (10%) presenta tions, comprised of a 6-day baseline period followed by 6 days of treatment where animals were given one of three doses of caffeine (2.5, 5 or 10 mg/k g) or saline prior to ethanol presentation. A final B-day post-treatment pe riod followed treatment. These results revealed an inverted-U effect of caf feine dose on ethanol ingestion where the low and high caffeine doses produ ced no effect but the moderate dose of 5 mg/kg enhanced ethanol drinking th at persisted throughout the post-treatment period. A third experiment revea led that caffeine did not alter levels of blood ethanol within the time per iod used for the ethanol drinking session. (C) 2000 Elsevier Science Inc. A ll rights reserved.