Effects of hyperprolactinaemia on core temperature of the rat.

The effects of endogenous hyperprolactinaemia (HPRL), as induced by pituitary homografts under the kidney capsule, on core temperature (Tc) was investigated in rats before and after the application of restraint stress. HPRL was accompanied by a significant decrease in Tc of freely moving rats, as observed for four days after pituitary homografts. HPRL-induced hypothermia was totally reversed by intraperitoneal (IP) injection of naloxone. In normoprolactinaemic (NPRL) rats, IP administration of naloxone caused a small but significant decrease in Tc and attenuated rise in temperature following the application of restraint stress. After application of restraint stress, Tc of HPRL rats raised to the level of unstressed NPRL rats. However, HRPL rats injected IP with naloxone showed no increase in Tc after restraint stress application. The effects of HPRL on Tc seem to involve an opioid component, and support the concept of a role played by stress hormones of hypophyseal origin in the control of Tc.