The effect of interrupted alcohol supply on spontaneous alcohol consumption by rhesus monkeys.

The alcohol supply (a 16% and a 32%, v/v, ethanol-in-water solution) for eight male rhesus monkeys, who already have had free access to water and ethanol solutions concurrently for about one year, was interrupted for 1, 2 or 7 days. The previously acquired ethanol consuming behaviour appeared very resistant to extinction, because ethanol consumption was immediately resumed after renewed access, even at a temporarily increased level. Since physical withdrawal distress was not observed and the increase was higher when interruption lasted longer, the observed behaviour could be attributed to the reinforcing effects of ethanol, leading to specific ethanol-directed behaviour.