The effect of alpha-interferon, cyclosporine A, and radiation-induced immune suppression on morphine-induced hypothermia and tolerance

An interconnection between the immune and the central nervous systems has been suggested by investigators studying the actions of several types of immune modifying agents and procedures upon opiate related phenomena. These studies have included the effects of altering immune system function by administration of either alpha-interferon, cyclosporine or radiation exposure upon naloxone-precipitated opiate withdrawal and upon opioid antinociceptive effects. The present study extends these earlier investigations by examining the effect of immune modulation upon opiate induced hypothermia. The results demonstrate that interferon and cyclosporine have no effects on baseline temperature or morphine induced hypothermia, while irradiation exposure elicits hyperthermia without affecting morphine-induced hypothermia. Finally, neither cyclosporine nor irradiation affect the development of tolerance to morphine induced hypothermia, while a single injection of the immune system modifier interferon was able to prevent the development of such tolerance. These observations suggest that yet another opiate-related phenomenon may be regulated at least in part by the immune system. These results together with our previous findings are further evidence of a link between the immune system and the CNS mediated through the opioid system. In addition, these studies further support our earlier hypothesis that "Interferon" is one of the endogenous substances which serves to prevent the development of tolerance and dependence to endogenous opioids.