Ethanol palatability and consumption by high ethanol-drinking rats: manipulation of the opioid system with naltrexone

Three experiments examined the effect of acute naltrexone treatment on both taste reactivity and consumption of ethanol in high ethanol-preferring rat lines: Alko Alcohol-Accepting (AA) rats (Experiments 1 and 2) and Alcohol-Preferring (P) rats (Experiment 3). A 3.0 mg/kg naltrexone dose was ineffective at altering ethanol palatability for either line, whereas 7.5 mg/kg was effective at reducing palatability of 10% ethanol for AA, but not P, rats, as reflected by both a decrease in ingestive responding and an increase in aversive responding. The effects of naltrexone on ethanol consumption were quite consistent: At both dosages, acute naltrexone treatment significantly decreased consumption of 10% ethanol. Termination of naltrexone resulted in an immediate increase in ethanol consumption to control levels. Results show that ethanol palatability and consumption can be dissociated in the rat and that the organization of opioidergic mechanisms that mediate ethanol responses may vary between rat lines.