Effects of voluntary exercise on severity of naloxone precipitated morphine withdrawal signs in rats

  Introduction: Addiction is a chronic disorder that requires long-term drug treatments. However, the most drug treatments programs have limited success. The aim of the present study was to investigate the effects of voluntary exercise on naloxone-precipitated morphine withdrawal signs in rats .   Materials and Methods: All rats were individually housed in cages with a free access to a running wheel and received subcutaneous injection of saline or morphine (10 mg/kg) twice per day at 12 hr intervals for 10 days. Non-runner groups were confined to the similar cages with no access to the wheels, but treated by morphine or saline. Morphine dependent intensity was examined by acute morphine withdrawal and naloxone injection (2 mg/kg, IP) according to a modified version of the Gellert–Holtzman scale.   Results: The results showed that there was no significant differences between control and morphine treated groups in running rates for a period of 10 days, indicating no effect of morphine on running activity. Withdrawal signs including abdominal contractions, wet dog shakes, weight loss (24h) and overall Gellert–Holtzman score were significantly lower in the exercising morphine treated rats as compared with non-exercising control rats (P= 0.0001).   Conclusion: Our findings indicated that the physical activity diminishes severity of dependency on morphine. Thus, it could be a potential natural reward method for substituting with the others of care methods.