Characterization of the effects of the acute and chronic administration of phencyclidine on body temperature in the rat: lack of evidence for the involvement of opiate receptors.

The present study characterized the effects of the acute and chronic administration of phencyclidine on body temperature in the rat. The acute administration of phencyclidine produced hypothermia. This hypothermia occurred only after high doses of drug. In contrast, only hyperthermia was found in chronically treated subjects. The hyperthermia in chronically treated subjects was produced by low doses of drug, and sensitization to the hyperthermic effects took place over time. There was no evidence for the involvement of opiate receptors in the acute hypothermic response to phencyclidine, as the hypothermia was not antagonized by naloxone or decreased in chronically morphine-treated subjects. Moreover, the hypothermic response was enhanced by treatment with opiate receptor-active and -inactive enantiomers of naloxone, as well as in chronically morphine-treated subjects.