Effects of time-of-day and photoperiod phase shifts on voluntary ethanol consumption in rats.

Two experiments were conducted to examine the circadian fluctuations in voluntary ethanol (ETOH) consumption in male Sprague-Dawley rats conditioned to consume ETOH in their homecage and exposed to photoperiod phase shifts equivalent to those experienced by humans. Using a maintenance concentration of 20% w/v ETOH, changes in homecage drinking in 42 rats were assessed after photoperiod phase shifts similar to those inducing "jet lag" in humans and after experimenter-induced "hangover." A single 8-hr photoperiod phase advance significantly increased ETOH intake for three consecutive days, and a single photoperiod phase-delay increased intake only on the day of the phase shift. Acute ETOH withdrawal significantly reduced the voluntary consumption of ETOH for two consecutive days. In a second group of 30 rats maintained to consume a lower concentration of 10% w/v ETOH, the long-term effects of "shift lag" initiated by repeated photoperiod phase shifting similar to those experienced by humans working under a rotating work schedule were examined. Significant increases in intake occurred over the 2-month testing period. The significant alterations in voluntary intake initiated by the shift work schedule was related to the significant changes in blood alcohol concentrations.