Voluntary ethanol consumption in the absence of hunger and thirst drives.

Voluntary ethanol consumption in Wistar rats was examined in a choice situation between water and ethanol. In each session continuing over 5 days, ethanol at five different concentrations from 2.5 to 45% (v/v) and water were given as reinforcers for FR-30 lever-press responses during 12-h light and 12-h dark periods with food available. The results indicated that rats preferred 2.5-5% ethanol to water, but water to 30 or 45% ethanol. Daily net ethanol consumption per kg body weight increased monotonically as a function of its concentration and reached a mean value of 9.08 g/kg at 45%. Rats drank most of the ethanol and water during the dark period, despite the large amount of ethanol intake occurring at that time.