Does exercise deprivation increase the tendency towards morphine dependence in rats?

Background Exercise deprivation has been concluded to have some negative effectson psychological well-being. This study was conducted to find outwhether exercise deprivation may lead to morphine dependence in rats. Methods Forty male Wistar rats weighing 162 ± 9 g were housed in clear plasticcages in groups of two under standard laboratory conditions. The studyhad two phases. In phase I, the animals were randomly divided intoexercised (E) and unexercised (UE) groups (n = 20 each) and treadmillrunning was performed based on a standard protocol for three weeks. Atthe end of the training period, plasma β-endorphin levels weredetermined in four rats from each group. In phase II, the animals wereprovided with two bottles, one containing tap water and the other 25mg/l morphine sulfate in tap water for a total of 12 weeks. At the end ofthis phase naloxone was injected intraperitoneally to precipitatemorphine withdrawal. Findings There was no significant difference between UE and E groups inmorphine consumption (mg/kg/wk) [group: F(1,14) = 0.2, P = 0.690; time:F(11,154) =18.72, P < 0.001; interaction: F(11,154) = 1.27 , P = 0.245]. Nostatistically significant difference between the two groups of animals wasseen regarding withdrawal signs. Conclusion The study showed that discontinuation of exercise does not increasethe tendency of morphine dependence in rats.