Subjects were adult (approximately 90 days old at the start of the experiment), ethanol-naïve, male selectively-bred P rats from the 61st generation. The rats were single-housed on a reverse 12 hr/12 hr dark-light cycle (light off at 0900 hr). Animals had ad libitum access to food and water. Rats were randomly divided into two groups: (1) the water control group (n = 18) had access to water as their sole fluid; and (2) the ethanol group (n = 30) received daily three 1-hr access periods to 15 and 30 % (v/v) ethanol separated by 2 hr starting 1 hr into the dark cycle (i.e., 1000—1100, 1300—1400, 1600—1700) for 5 consecutive days each week. Multiple concentrations, instead of a single concentration, of ethanol were used to further increase alcohol intakes (Rodd-Henricks et al., 2001). The animals did not have access to ethanol on weekends. Measurements of water and ethanol intake, and body weights were taken Monday through Friday at 1100 hr; ethanol intakes were determined at the end of each 1-hr access period.
