The Role of Endogenous Opioids in The Thermoregulatory Capacity of Aged Rats

It has been shown that endogenous opioids are involved in the adaptive mechanisms related to stress. The adaptive competence of an organism is known to decline with age. In this experiment, age related changes in the thermoregulatory capacity of rats and the role of endogenous opioids in this mechanism were studied using the ice-water immersion test. Young (7-8 month old) and old (16-18 month old) rats were used. Opioid activity was evaluated indirectly using the specific opiate antagonist naloxone. Restoration of body temperature was significantly slower in old rats (p<0.05). Following naloxone administration, there was an increased drop in rectal temperature and a decreased rate of recovery in old rats (p<0.05). This indicated that the thermoregulatory response was significantly impaired in old rats when compared to young rats. It is concluded that a naloxone-reversible opioid activity plays a role in thermoregulatory competence. This role appears to be more critical with increased age.