Evidence against a biphasic effect of acetaldehyde on voluntary ethanol consumption in rats.

A group of 27 male Long-Evans rats was given a 2 week period of free-choice ethanol and consumed 1.26 +/- 1.27 g/kg/day (mean +/- SD). The animals were then divided into 3 groups. One group received the aldehyde dehydrogenase inhibitor, cyanamide, in their diet and an oral ethanol dose of 2 g/kg for 5 days. Another group received only the oral ethanol dose and the third, control, group received no treatment during these days. After the forced cyanamide and/or forced ethanol treatment, all of the rats were returned to the choice situation. Voluntary ethanol consumption was then followed for 2 months, during which time the control rats steadily increased their ethanol intake to 3.6 +/- 2.1 g/kg/day (mean +/- SD of last week's consumption). The cyanamide treatment caused a transient (3--4 day) decrease in the ethanol intake, after which the consumption increased to 3.7 +/- 2.9 g/kg/day. Consumption by the forced ethanol group (5.4 +/- 2.0 g/kg/day) was significantly greater (p less than 0.05) than that by the other rats. The present results do not favor a physiological role for acetaldehyde-induced formation of alkaloids in increasing voluntary ethanol consumption, but do support the notion of an acetaldehyde-mediated aversive effect on ethanol drinking.