Effects of exercise and supraphysiological dose of nandrolone decano-ate on the rat plasma opioid level: a brief report

Background: Anabolic-Androgenic Steroids (AAS) are mainly abused by athletes for improvement of muscle performance. Data suggest that the effect of AAS on neurobiochemicals related to behavioral response, may be underlies psychological adverse effects. Physical activity has beneficial psychophysiological effects, which may be related to increased serum levels of endogenous opioid peptides during exercise. In the present study we aimed to study the effect of chronic administration of nandrolone decanoate on beta-endorphin and met-enkephalin level in exercising rats. Methods: In this experimental study, forty male Wistar rats were randomly assigned in two main groups of sedentary and trained (2 weeks swimming exercise). Animals in each group were divided in two subgroups of control (received nandrolone solvent) and drug treatment (received nandrolone 15 mg/kg, 5 times/week). After two weeks of swimming exercise and drug treatment, serum levels of beta-endorphin and met-enkephalin were measured using ELIZA. Results: Our data showed that two weeks of swimming exercise training significantly increased serum beta-endorphin (114±5 vs. 98±5 ng/l in control group, P= 0.038) and met-enkephalin levels (1556±42 vs. 1475±27 ng/l in control group, P= 0.25). However, chronic administration of nandrolone decanoate in trained group considerably de-creased beta-endorphin (84±4 vs. 114±5 ng/l in control group, P= 0.002) and met-enkephalin levels (1378±36 vs. 1556±42 ng/l in control group, P= 0.011). The effect of supraphysiologic doses of nandrolone decanoate in control sedentary group was not statistically significant. Conclusion: In the present study we show that chronic nandrolone decanoate admin-istration attenuates effects of two weeks swimming exercise on serum opioid peptide and reduces the level of beta-endorphin and met-enkephalin. Keeping in mind that opi-oidergic system play an important role in behavior, athletes abusing anabolic steroid drugs may potentially experience changes in mood and behavior.