EFFECT OF DERMORPHIN ON THERMOREGULATION IN RATS AT SELECTED AMBIENT-TEMPERATURES

Intraperitoneal administration of dermorphin caused dose-dependent cha nges in rats core temperature and tail skin temperature (indicative of compensatory thermoregulatory vasoreactions in rats). The character o f these changes depended strongly on the environmental temperature at which the inversion of the dermorphin-induced thermoregulatory effect was observed. In the cold environment (4-7 degrees C) dermorphin cause d a significant, stable, dose-dependent hypothermia. In the thermoneut ral environment (27-28 degrees C) dermorphin also caused hypothermia, but this effect was less pronounced. In the hot environment (31-32 deg rees C) dermorphin caused hyperthermia. Dermorphin-induced changes in tail skin temperature indicate that dermorphin suppresses the thermore gulatory peripheral compensatory vasomotor reactions. Pretreatment wit h naloxone attenuated dermorphin-induced effects on core temperature a nd partially enhanced vasomotor effects of dermorphin. The data obtain ed indicate that dermorphin affects the core temperature regulation vi a mu-opiate receptors, whereas vasomotor effects of the peptide are pr obably mediated via naloxone-insensitive receptors.