Peripheral naloxone attenuates lipopolysaccharide fever in guinea pigs by an action outside the blood-brain barrier

Subcutaneous infusion of tertiary mu-receptor opioid antagonist naloxone hydrochloride (Nal-HCl) weakens the febrile response of guinea pigs to liposaccharide fever. Nal-HCl exhibits a central hypothermic action, a peripheral thermolytic action and a peripheral antipyretic action. The peripheral antipyretic action of Nal-HCl confirms the necessity to circulate opioids in the fever generation in guinea pigs.