Effect of dermorphin on body temperature in rats.

The effect of dermorphin on regulation of body temperature was studied in the rat under extreme and thermoneutral environmental temperatures and in different nutritional states. Intracerebroventricular (icv) injections of dermorphin at dose levels of 10, 50, 100 ng/rat produced hypothermia in animals placed in cold temperatures (-10 degrees C and +4 degrees C) and hyperthermia at ambient (+22 degrees C) and higher temperatures (+34 degrees C). These data emphasize the importance of using a wide range of environmental temperatures in studying drug effects on thermoregulation. To determine whether the effect of dermorphin on body temperature was related to the nutritional state of the animal, as observed with other neuropeptides (i.e., bombesin, litorin), the thermoregulatory response was followed in fed and fasted rats. The same results were obtained in both experimental groups. In all cases, dermorphin change in body temperature was mediated via an action on typical opioid receptors since it was completely prevented by pretreatment with naloxone.