The effects of single dose administration of opium on muscular and central fatigue in male rats

Introduction: Exhaustive exercise leads to muscle fatigue and reduces muscle power in response to contractile activity and causes central fatigue. On the other hand, the effects of opioids on skeletal muscles and fatigue phenomenon are not known completely. Thus, the current study aimed to assess the effect of a single dose administration of opium on muscle and central fatigue in male rats. Materials and Methods: In this experimental study, 21 male Wistar rats weighing 220-270 g were randomly divided into three equal groups: control, opium receiving group, opium without swimming (sham opium). In order to evaluate muscle fatigue, swimming test was used and for central fatigue the sedation score was used. At the end of the experiments, blood samples were obtained from animal eyes and were sent to the laboratory for measurement of muscle fatigue indices including lactate dehydrogenase (LDH) and creatine phosphokinase (CPK). Data were analyzed using ANOVA, T-test and SPSS software. Results: Data showed that the swimming time in animals receiving opium was significantly lower than control group (P<0.001). Data also revealed that central fatigue in opium group was significantly lower than control animals (P<0.001). Moreover, opium alone and without swimming test caused central fatigue in animals (P<0.05). Conclusion: The present study showed that administration of a single dose of opium in rat’s increases muscle fatigue. Moreover, opium administration reduced central fatigue in rats.