Selected opioids modify intake of sweetened ethanol solution among female rats

Water-deprived female rats were given a daily, 1.5-hr opportunity to take either a sweetened ethanol solution or water. Across days, they increased their intake of ethanol solution and had stable intakes of about 2 g of pure ethanol/kg after 3 weeks. Morphine (1.0 mg/kg) alone, and in combination with diprenorphine (25 micrograms/kg), increased intake of ethanol solution among females similar to the increased intake seen with males under similar procedures. Fentanyl dose-relatedly increased intake of ethanol. The data strengthen the idea that one or more of the endogenous opioid systems, but not all, are involved with instances of "excessive" intake of alcoholic beverages.