ETHANOL REGULATED PREFERENCE IN RATS

A series of experiments evaluated the determinants of preference for m ixtures of ethanol plus sucrose relative to sucrose in rats. One dippe r served 10% ethanol mixed with 10% sucrose, and the second dipper ser ved 10% sucrose. Lever presses operated each dipper according to a var iable-interval 5-s schedule. In three experiments the subjects were gi ven pre-session meals of sucrose (2.5-20 ml) or sucrose (20 ml) plus c how (5 or 10 g). Pre-session meals decreased responding maintained by sucrose but not responding maintained by ethanol mixture. In two exper iments body weight was varied from 85% to 125% of the initial free-fee ding values. Increases in body weight, like pre-session meals, decreas ed responding reinforced by sucrose, but typically did not decrease re sponding reinforced by ethanol mixture. Throughout most of the study, ethanol consumption remained at about 1.25 ml per half hour session (3 -4 g/kg per 30 min). For example, pre-session access to ethanol mixtur e decreased within-session ethanol consumption, but total consumption, counting both sources, remained about 1.25 ml/session. The within-ses sion patterns of responding also differed. Responding reinforced by et hanol mix decreased as a function of ethanol consumption, whereas resp onding reinforced by sucrose was relatively constant throughout the se ssion. The simplest explanation of the results is that ethanol's pharm acological consequences regulated preference.