Pattern of daily blood ethanol elevation and the development of physical dependence.

Schedule-induced ethanol polydipsia regimens were used which produced either one or two daily peaks in blood ethanol levels. After 3 months on these regimens, rats were withdrawn from ethanol and tested for the presence of abstinence signs. No evidence of physical dependence was found, a result which contrasted with the previous finding of a severe withdrawal syndrome when blood ethanol was maintained at a more continuously elevated level prior to withdrawal. It was concluded that, as in the case of barbiturates, the development of physical dependence on ethanol requires more than an episodic peaking of the blood ethanol level once or twice per day.