Voluntary ethanol intake in rats following exposure to ethanol on various schedules

Voluntary intake of 20% (v/v) ethanol solutions was assesed in groups of male Wistar rats following various forms of ethanol exposure. Some animals were first exposed to gradually increasing weak solutions of ethanol (acclimation); while others were given 20% solutions from the start. Some were given ethanol every day (continuous schedule); others were given ethanol every other day (intermittent schedule). Some were given ethanol solutions with plain water also available (free-choice); others were given ethanol solutions as the only fluid available (forced-choice). The animals on intermittent schedules for a 30 day period developed a slight preference for 20% ethanol solutions; they came to drink an average of over 9 g/kg/day of absolute ethanol when tested in free choice conditions. Previous acclimation did not add significantly to this effect. The effect held whether the animals received their ethanol in free- or forced-choice conditions. Forced-choice experience inhibited subsequent free-choice intake in the continuous-exposure group, but forced-choice coupled with intermittent exposure led to the highest intake levels in the shortest total ethanol exposure. The intake levels of these animals are encouraging for those interested in developing animal analogues for human ethanol abuse.Supported by grants from the Licensed Beverages Industries and the Medical Research Council of Canada.