Generalization of behaviorally augmented tolerance to ethanol, and its relation to physical dependence

Adult rats, required to perform a motor coordination task while under the influence of ethanol (2.2 g/kg) daily for 12 days, developed significant tolerance to the effects of ethanol, not only on this test but also on a food-motivated maze task. At the same time, they showed reduced shock threshold for production of a startle response, and reduced open field test scores 23 hrs after the last dose of ethanol. Other animals receiving the same dose of ethanol immediately after each training session on the coordination task, and others performing the task and receiving no ethanol, showed no tolerance on either test and no change in shock threshold or open field behavior. The results suggest that behaviorally augmented tolerance depends on basic neuronal adaptive changes indistinguishable from those accompanying physiological tolerance and dependence.