Previously it was found that during the loss of postural support induced by combined administration of haloperidol and morphine, rats became markedly hypothermic. The present work was a more detailed study of this hypothermia. Morphine alone (20 mg/kg) produced a slight hyperthermia (1∞C) in female rats and no effect in males. Haloperidol alone (5 mg/kg) elicited a hypothermia of about 3∞C in females and no effect in males. The combination of both elicited a greater decrease of temperature (about 5∞C) in female rats and, unexpectedly, a decrease of 3∞C in males. According to these data, increased endorphinic activity with a concomitant decrease in dopamine in some unidentified regions of the central nervous system causes hypothermia. © 1987.
