EFFECTS OF SUCROSE-SUBSTITUTION INITIATION ON PATTERNS OF DRINKING BYLEWIS RATS DURING CONTINUOUS ALCOHOL ACCESS

Initiation of alcohol drinking using the sucrose-substitution procedur e was studied in inbred Lewis rats. One group of animals was initiated to self-administer alcohol prior to being placed in the continuous-ac cess condition, whereas the second group of animals did not undergo in itiation. During the continuous-access period, the animals were housed in operant chambers where they had continuous access to alcohol (10% v/v), food, and water during daily 23-h experimental sessions. After 5 weeks of baseline conditions, the response requirement for food was i ncreased over weeks. This was followed by weekly increases in the etha nol response requirement with the food response requirement returned t o baseline conditions. In the continuous-access condition, both groups consumed similar amounts of alcohol by the end of the 4-week baseline period and showed similar numbers of dippers presented per alcohol bo ut and number of alcohol bouts per day. During the food response requi rement manipulation, alcohol consumption increased for both groups but intake increased significantly more for the noninitiated group. The d ifference between groups was accounted for by a larger number of alcoh ol drinking bouts per day for the noninitiated group. Alcohol consumpt ion decreased at each increase in ethanol reinforcement response requi rement for both groups. Alcohol-reinforced responding per session incr eased for the noninitiated animals but remained unchanged for the init iated group during this condition. Responding increased substantially for both groups when the alcohol reinforcement response requirement wa s returned to baseline conditions. These results suggest that alcohol may serve more as a food source for noninitiated animals during the fo od reinforcement manipulation and that initiation may result in more r esistance to change during the alcohol reinforcement manipulation. The se data show that the type of initial exposure to alcohol can impact f uture drinking patterns. (C) 1997 Elsevier Science Inc.