A comparison of the effects of morphine and pethidine upon body temperature and the reversal of reserpine's effects upon body temperature in the mouse.

The effects of morphine and pethidine upon body temperature and upon the reversal of reserpine hypothermia in the mouse were investigated. Both morphine and pethidine produced a dose-dependent fall in body temperature, that of morphine being totally antagonized by nalorphine and partially by naloxone, while that of pethidine was antagonised by naloxone and enhanced by nalorphine. Both drugs reversed reserpine-induced hypothermia. The reversal by morphine, but not by pethidine, was partially antagonized by naloxone. Adrenalectomy prevented the reversal of reserpine hypothermia by pethidine but morphine produced a partial reversal. Ganglion blockade and alpha-and beta-blockade all prevented reversal of reserpine hypothermia by both drugs. The results are discussed with regard to differences between pethidine and morphine and possible involvement of opiate receptors.