The lack of effect of opioid agonists and antagonists on some acute effects of ethanol.

We studied the ability of opioid antagonists: naloxone, naltrexone and diprenorphine and an opioid agonist morphine to influence the effects of ethanol on hypothermia, sleeping time and impairment of aerial righting reflex. Naltrexone (2-16 mg/kg) and naloxone (2-16 mg/kg) were not able to attenuate effects of ethanol, while diprenorphine decreased ethanol sleeping time (4 microgram/kg) and antagonized the ethanol hypothermia (8 microgram/kg). Naltrexone in a dose of 8 mg/kg sc antagonized the ethanol impairment of aerial righting reflex. The present behavioral studies did not provide any evidence for the participation of the opioid system in the mediation of acute ethanol effects in rats.