Forced ethanol treatment stimulates and inhibits ethanol intake in a rat model of alcoholism.

In a model of psychological dependence, a very stable ethanol intake was induced by a chronic (1-year) intermittent (once a week) exposure to intoxicating amounts of ethanol (24 h choice between ethanol and water, followed by 2.0 g/kg i.p.). After this year, the rats had continuous access to ethanol and water. Stability was shown by the ability of the rats to take the same dose of ethanol (in g/kg) when the concentration was changed from 10 to 20%. To study possible priming or inhibiting effects on ethanol intake, ethanol was injected i.p., first as 20%, 40% or 60% of the intake in the 24 h prior to the injection, then as fixed doses of 0.5, 1, and 2 g/kg, and the ethanol intake during the following 24-h period was recorded. The results showed that, following a low dose of ethanol, voluntary ethanol intake was increased in rats with a low, and decreased in rats with a high, ethanol intake, while high doses of ethanol seemed to decrease voluntary ethanol intake in all rats. The results are discussed in relation to theories about loss of control of drinking and relapse in humans.