The effect of antagonists selective for mu- and delta-opioid receptor subtypes on alcohol consumption in C57BL/6 mice.

Several studies have demonstrated that non-selective opioid receptor antagonists effectively reduce alcohol consumption in both animal models and at the clinical level. However, research examining the contribution of specific opioid receptor subtypes to this effect has yielded conflicting results. Some of these studies have shown that the effect is contingent upon the action of mu receptors while others have suggested that delta receptors are primarily responsible. The data reported here re-examine this question using the alcohol-preferring C57BL/6 mice. The results of this experiment demonstrate that D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP), a mu-selective antagonist, and naltrindole, a delta-selective antagonist, are equally effective at reducing alcohol consumption in a limited access model compared to a saline control group. While there was no specific comparison of the effects of these drugs on alternative appetitive behavior, neither of these drugs had effects on measured off-session food or water consumption. The results of this experiment suggest that alcohol consumption is mediated by both mu- and delta-opioid receptor subtypes.