RESUMO
Background and Aim: Endogenous opioids and addictive opiate drugs change many body functions. Previous studies have referred to the effects of morphine on smooth and pulmonary muscles, but the effects of opioids on skeletal muscles is not known well. Thus, the current study aimed at assessing the effect of a single dose of morphine on muscle fatigue in male rats
Materials and Methods: In this experimental study, 40 male Wistar rats weighing 220-270 g were randomly divided into four equal groups: control [the mice were kept in their cages and received food and water], morphine receiving group, fatigue group [the mice in this group were kept running on a treadmill. for120 minutes at a rate of 20 meters per minute], and morphine plus fatigue group. At the end of the experiments, blood samples were obtained from the corner of their eyes and were sent to the laboratory for measurement of muscle fatigue indexes including lactate dehydrogenase [LDH] and creatine phosphokinase [CPK]
Results: Administration of morphine to the fatigue group decreased running time compared with the control group [P=0.009]. Furthermore, administration of morphine to the fatigue group significantly increased serum levels of LDH [P=0.009] and CPK [P=0.008]
Conclusion: The present study showed that administration of a single dose of morphine in rats increases muscle fatigue biomarkers [LDH, CPK]
RESUMO
Morphine addiction and morphine withdrawal syndrome are the two main problems of today's human society. The present study has investigated the effects of nicotine on the strength of physical and psychological dependency in single and repeated doses morphine administrated rats. Male Wistar rats were subjected to morphine consumption with single or frequent dose protocols. In the single dose protocol, rats received only one dose of morphine and 24hrs later they also received one dose of nicotine 30 min prior to injection of naloxone. In the repeated dose protocol, rats received incremental doses of morphine for 7 days and 24hr after the last dose [the 8th day] were given naloxone. However, the nicotine regimen of this group was injected 15 min before the morphine injection, for 4 days, from the 4th to the 7th day. Five minutes after naloxone injection, each rat's behavior was captured for 30 min, and then physical and psychological signs of withdrawal syndrome were recorded. Data were analyzed by ANOVA followed by Tukey tests and p<0.05 was considered as significant difference. Results showed that the injection of frequent and single doses of morphine lead to morphine dependency. In single dose protocol, nicotine consumption attenuated the signs of withdrawal syndrome, especially weight of excrement and total withdrawal score. In frequent dose protocol, in addition to these effects, nicotine induced weight loss and place aversion. The inhibitory effects of nicotine on signs of withdrawal syndrome may involve a dopaminergic portion of the central nervous system and is mediated by central nicotinic receptors. There is also a cross-dependence between nicotine and morphine