SUPPRESSANT EFFECTS OF NALOXONE ON FOOD AND WATER-INTAKE IN THE RAT

Systemic administration of naloxone to food- or water-deprived male, Sprague-Dawley rats suppresses food and water intake in a dose-dependent fashion. Administration of as little as .1 mg/kg naloxone significantly reduces water intake. Morphine also reduces water intake in a dose-related manner. Nonetheless, when morphine and naloxone are given together at various doses, a competitive interaction is seen, suggesting that the suppressant effects of these drugs are, in part at least, mediated by the same opiate receptors. High (10 mg/kg) but not low (.1 mg/kg) doses of naloxone induce conditioned taste aversion; thus, sickness may be the cause of the suppressant effects of high, but not low, doses of the drug. These findings are discussed in relation to the hypothesis that endogenous opioid substances mediate drive-reduction reward. © 1979 Academic Press, Inc.