Role of Testosterone in Swimming Exercise-induced Analgesia in Rats

  Objective: “Feel good effect” of exercise is well known. Activation of pain inhibitory mechanisms after exercise is also well documented. Swimming is considered as a beneficial exercise as well as health-promoting sport. The significance of testosterone in swimming exercise-induced analgesia is yet to be understood. Therefore, it is worthwhile to investigate the significance of testosterone in swimming exercise-induced analgesia. Materials and Methods: The basal tail flick latencies of all animals were recorded by using tail flick analgesiometer. In order to observe the effect of testosterone on swimming exercise-induced analgesia, testicles of animals of some groups were surgically removed. Then animals were subjected to swimming sessions of different patterns. After swimming, tail flick latencies were measured. Results: Swimming sessions resulted in increase in pain thresholds of all animals. Castration negatively affected the degree of analgesia achieved in rats. However, daily treatment of testosterone propionate (500µg/kg, s.c.) improved swim-induced analgesia in castrated rats. Moreover, daily administration of naloxone hydrochloride (1mg/kg, i.p.) fifteen min prior to swimming suppressed testosterone therapy resulted in an increase in swim-induced analgesia in castrated animals. Conclusion: We concluded that testosterone plays a significant role in swimming exercise-induced analgesia in male Wistar albino rats and this positive effect of testosterone on pain threshold might be mediated through its probable effect on the endogenous opioid system.