Effects Of Electroacupuncture On Met-Enkephalin Level In The Central Nuclei Of Exercise-induced Fatigue Rats

Exercise-induced fatigue is frequently happened under exercise training but difficult to be dealt with. Fatigue can be relieved through pharmacologic treatments and non-pharmacologic modalities. The pharmacologic is satisfactory but has side effects and not permitted by the competition. The non-pharmacologic are worth popularizing with the reliable effects and the little side effects. Of the non-pharmacologic, electroacupuncture（EA） is widely applied since it is relatively easy to be controlled and its effects is reliable. It has been known that, EA can decrease the accumulation of metabolites during exercise including the blood lactate acid and blood urea nitrogen, and increase the content of hemoglobin and glucose, thus relieve the fatigue and recover the capability of exercise. Studies have shown that exercise could stimulate release of the endogenous opioid peptides. Enkephalin had a role in many physiological regulations including cardiovascular and respiratory functions, thus benefited for the capability of exercise and improve the metabolism of body. EA could regulate the release of central enkephalin（ENK）, while whether EA regulate the fatigue mediated through the central ENK is less investigated. Present study applied the treadmill running fatigue model and cure the exercise rats using EA to explore the effects of EA on the ENK level of central nuclei and probe into the central mechanism of EA on the fatigue.Eighty-four male and healthy SD rats（weighting 200±20g） were randomly divided into four groups: control group, exercise group, EA group and exercise + EA group,. Each group had 21 rats. Rats in exercise group were trained with treadmill for 7 weeks, the first five weeks were adaptive exercise and the 6th and 7^th week were high intensity exercise. Rats in EA group were electroacupunctured（2/100Hz） in “Zusanli” bilateral acupoints for 15 min every 2 days.. Rats in exercise + EA group were first trained and then electroacupunctured, the training method was same with exercise group and after 3h rest rats were electroacupunctured same with exercise + EA group. Rats in control group were not treated with treadmill and electroacupuncture. 7 rats were respectively selected for blood sampling and brain sampling at the 5th, the 6th and the 7^th week. The blood samples were to measure the blood biochemical indexes including blood lactate acid, blood urea nitrogen and glucose using the Vet Test Chemical Analyzer. The brain samples were to measure the met-enkephalin（M-ENK） immune activity level in central nuclei including globus pallidus（GP）, caudate putamen nucleus（CPU）, accumbens nucleus（ACB）, amygdala（AMY）, parabrachial nucleus（PBN）, solitary nucleus（SOL） and gigantocellular reticular nucleus（GRN）.Blood biochemical indexes results showed that, blood lactate acid, blood urea nitrogen and glucose in all groups didn`t have significant change at the 5th week. Blood lactate acid and blood urea nitrogen in exercise group were higher than control group at the 6th and 7<sup>th</sup> week（P < 0.05）. Blood lactate acid and blood urea nitrogen in EA group were lower than exercise group at the 6th and 7<sup>th</sup> week（P < 0.05）. Blood lactate acid and blood urea nitrogen in exercise + EA group were lower than EX group at the 7<sup>th</sup> week（P < 0.05）. Glucose in exercise group at the 7<sup>th</sup> week was lower than C group and glucose at the 7<sup>th</sup> week in exercise + EA group was higher than exercise group, but these changes weren`t significant（P >0.05）.Influence of EA on the immune activity of different nuclei in exercise rats were diverse. In GP, M-ENK immune activity in exercise group at the 5th and the 6th week had no significant change comparing with the control group and it was lower than control group at the 7^th week（P < 0.05）. M-ENK in exercise + EA group at the 5th week had no significant change comparing with the control and it was higher than exercise group at the 6th and the 7^th week（P < 0.05）. In ACB and CPU, M-ENK immune activity in exercise group was higher than C group at the 7^th week（P < 0.05） and M-ENK in exercise + EA group at the 7^th week was lower than exercise group（P < 0.05）. In AMY, PBN and SOL, M-ENK immune activity in EX group at the 5th week was higher than control group（P < 0.05）and it didn`t change significantly at the 7<sup>th</sup> week comparing with the control group（P >0.05）. In PBN and SOL, M-ENK in exercise + EA group at the 7<sup>th</sup> week was higher than exercise group（P < 0.05）. In AMY, M-ENK in exercise + EA group at the 5th, 6th and 7<sup>th</sup> week were stable（P >0.05）. In GRN, M-ENK immune activity in exercise group didn`t change significantly at the 5th and the 6th week and it was higher than C group at the 7^th week（P < 0.05）. M-ENK in exercise + EA group at the 7^th week was also higher than exercise group（P < 0.05）. Comparing with C group, M-ENK immune activity in EA group was increased in all nuclei（P < 0.05）.This study exhibited that EA can decrease the content of blood lactate acid and blood urea nitrogen and increase the content of glucose, regulate the immune activity of M-ENK in GP, ACB, CPU, AMY, PBN, SOL and GRN and promote the recovery of exercise capability. This is beneficial to uncover the central effects of EA on exercise fatigue, and promote the development of exercise medicine as well as the application of acupuncture clinical medicine.