Effects Of Electro-acupuncture On Opioid Peptides Receptors In Inflamed Location In Inflammatory-Pain Rats

The previous studies suggested that endogenous opioid peptides (EOP) participate in the peripheral mechanism of electro-acupuncture (EA) analgesia for inflammatory-pain. This study observed the effects of EA on the opioid receptors gene expression in the inflamed location in inflammatory-pain rats, further sought to the peripheral mechanism of EA analgesia.32 SD rats were randomized into control group (n=8), EA group (n= 8), model group (n=8) and singly-EA group (n=8) . EA (2-4V, 20-100Hz) was applied to Xuanzhong and Kunlun points for 20min. The experiments used adjuvant arthritic (AA) rats as the model of inflammatory-pain, adopted immunohistochemistry and in situ hybridization histochemistry, and observed targets of pain threshold, local β - endorphin ( β - EP ) and leucineenkephalin (LEK), and the gene expression of the opioid receptors (MOR, DOR, KOR) in the inflamed location and etc.Results: (1)After EA treatment, compared with model group, the pain threshold of EA group increased significantly (P <0.01), but had no difference compared with control group (P >0.05); (2) The syntheses and release of the EOP in EA group were significant higher than those of model group (P <0. 01); (3)The opioid receptors (MOR, DOR, KOR) mRNA expression of EA group was considerabl higher than that of model group (P <0. 01) . The results showed that EA had definite analgesic effect for inflammatory-pain, promoted syntheses and release of the EOP and promoted the opioid receptors (MOR, DOR, KOR) mRNA in EA analgesia. Taken together, it is indicated that the peripheral analgesic mechanism is that EA probably promotes syntheses and release of the EOP and their receptors (MOR, DOR, KOR) to carry out the peripheral actionin inflamed location. The results also have certain reference value to approach the peripheral analgesic mechanisms of EA for chronic pain.