Importance of delta opioid receptors in maintaining high alcohol drinking.

We have previously reported that naloxone, a nonspecific opioid receptor antagonist, suppresses alcohol but not water consumption by male rats that have been genetically selected for high voluntary alcohol drinking. However, the identity of the specific opioid receptor subtype that may mediate alcohol drinking is not known. This paper reports that a selective delta opioid receptor antagonist is as effective as naloxone in suppressing alcohol consumption and that an enkephalinase inhibitor, which potentiates the action of endogenous enkephalins, increases alcohol intake. These results suggest that alcohol-induced activation of the endogenous enkephalinergic system, and occupation of delta opioid receptors, are involved in the maintenance of continued alcohol drinking.