Behavioral augmentation of tolerance to ethanol in the rat

Three groups of rats were trained on a circular maze task, then were tested under the influence of ethanol. Thereafter, all three groups received ethanol daily, on different schedules. One group (psychological) received ethanol (1.2 g/kg i.p.) just before each treatment session; another group (physiological) received the same dose immediately after the session; and the control group received only saline. All three groups were tested under ethanol every fourth day. The psychological group showed significant tolerance by the second test day, and maximal tolerance by the fourth. The physiological group reached the same maximum tolerance by the sixth test day, while the controls showed no increase in tolerance. Addition of daily gavage with ethanol (6 g/kg) did not modify the level of tolerance in the psychological or physiological groups, but raised the controls to the same level as the others. None of the changes in tolerance were attributable to increased rate of ethanol elimination. It is concluded that production of tolerance by these various techniques is distinguishable only with respect to rate.