Pharmacology Biochemistry & Behavior, Vol. 7, pp. 401-403. Copyright © 1977 by ANKHO International Inc. All rights of reproduction in any form reserved. Printed in the U.S.A. BRIEF COMMUNICATION Effects of Feeding Regimen on Ethanol Intake by Guinea Pigs' ALAN POLING, CATHLEEN URBAIN AND TRAVIS THOMPSON Psychiatry Research Unit, University of Minnesota, Box 392 Mayo Memorial Building Minneapolis, MT 55455 (Received 29 August 1977) POLING, A., C. URBAIN AND T. THOMPSON. Effects of feeding regimen on ethanol intake by guinea pigs. PHARMAC. BIOCHEM. BEHAV. 7(4) 401-403, 1977. - During daily two-hr sessions, guinea pigs licked a drinking tube filled with either 0 (tap water), 2, 4 or 8% (v/v) ethanol solution under three feeding regimens. Consumption of each solution was highest when sufficient food to maintain subjects at 90% of free-feeding weight was provided during sessions, lower when the same food ration was provided after sessions, and lowest when ad lib access to food was provided within and between sessions. However, this decrease in consumption across feeding regimens was inversely related to ethanol concentration. Under all feeding regimens, volume of solution consumed decreased with increasing ethanol concentration while milligrams ethanol consumed increased with ethanol concentration. These results are similar in some respects to previous findings with rats and monkeys, suggesting that further studies of oral ethanol self-administration by guinea pigs may be merited. Guinea pigs Ethanol Feeding regimen Self-administration THE INTERACTION between food deprivation, food presentation, and liquid intake is complex and apparently differs across species [3, 11, 19]. Schedule-induced poly- dipsia, the persistant drinking that occurs when food-depriv- ed animals intermittently receive dry food in small quantities, has been explored in rats [6, 7, 8, 12, 22], monkeys [17], and pigeons [18]. The effects of substituting ethanol solutions for water during schedule-induced drinking by rats have been examined [10,14]. Typically, volume of solution consumed decreases with increasing ethanol con- centration while milligrams ethanol consumed varies direct- ly with concentration. Following schedule-induced poly- dipsia, ethanol may serve as a reinforcer for rats tested in the absence of food (e.g. [ 7,11 ] ). When guinea pigs are food deprived, water intake may increase markedly [4]. The effects of introducing ethanol solutions during such hunger-induced drinking have not been examined. The present study determined intake of ethanol solutions of 0 (tap water), 2, 4 and 8% (v/v) concentration by food-deprived guinea pigs tested in the presence and absence of food. Consumption of each solution by guinea pigs given ad lib access to food was also examined. METHOD Animals Three adult male Hartley-derived guinea pigs were individually housed in a constantly-illuminated room with an ambient temperature of 24°C. Water was constantly available in home cages. Apparatus Three sound-attenuated Gerbrands operant conditioning chambers were modified by the addition of a drinking tube and a food cup to one side wall. The drinking tube was mounted 5 cm above the chamber floor and protruded 2.5 cm from the wall. The food cup was mounted 2.5 cm from the chamber floor immediately to the left of the drinking tube. A 25-W white house light provided ambient illumination. Electromechanical programming and recor- ding equipment was located in an adjacent room. Ethanol solutions (v/v) were prepared using 95% ethanol in tap water. Solutions were prepared at least 12 hr before use and stored in sealed flasks at room temperature. Pro ced u re Sixteen two-hr sessions were run under each of three feeding regimens. In Sessions 1 through 16, a portion of Purina guinea pig chow sufficient to maintain each animal at 90% of free feeding weight was presented in the experimental chamber. Any food not consumed within the session was returned with the animal to the home cage. In Sessions 17 through 32, the same amount of chow was The senior author is a predoctoral trainee under Psychopharmacology Training Grant USPHS MH-08565, which supported the research. Editorial comments of J. E. Henningfield on an earlier version of the manuscript are gratefully acknowledged. 401