ABSTRACT
Objective To investigate the change of mu opioid receptor ( MOR) in dorsal root ganglion ( DRG) in rat chronic inflammatory pain model and the effect of MOR agonist and antagonis tintraplantarly ( i.pl.) injected on pain threshold, so as to determine the role of peripheral MOR in chron in inflammatory pain .Methods Chronicin flammatory pain model was established by i .pl.injection of CFA in rats.The expression of MOR in DRG was detected by immunohistochemistry .Pain threshold before and after i .pl.injection of MOR agonist and antagonist was measured by radiant heat method .Results Rats suffered from an intraplantar injection of CFA developed chronic inflammatory pain , and the painthreshold still reduced on 18 day after CFA injection compared to that in the normal group . Immunohistochemistry staining revealed that compared with the normal group , the expression of MOR in DRG of CFA rats was increased ( P<0.01 ) .After the paw dorsal surface injection of MOR agonist , the pain threshold of CFA rats was increased, while that of normal rats exhibited no significant change .After the paw dorsal surface injection of MOR antagonist, the pain threshold of CFA rats was reduced , while that of normal rats had no significant change .Conclusion Under chronic inflammatory pain condition , DRG MOR expressionis enhanced , which participates in the regulation of chronic inflammatory pain , and may contribute to the prevention of further more serious pain .
ABSTRACT
<p><b>OBJECTIVE</b>To observe the analgesic effect of electroacupuncture (EA) on collagen-induced arthritis (CIA) rats and its regulating effect on inflammation reaction and the endogenous opioid system of synovial tissues. Methods A total of 30 healthy male Wistar rats were randomly divided into a control group, a model group and an EA group, 10 rats in each one. The chronic pain model of CIA rats was made by cattle type-II collagen in the model group and EA group. Rats in the EA group were treated with EA at "Zusanli" (ST 36) and "Kunlun" (BL 60) for 30 min from 16th day after model establishment, once a day for consecutive 10 days. Rats in the control group did not receive any treatment. Rats in the model group were treated with fixation as the EA group. Threshold of pain, arthritis index, paw swelling were measured before model establishment and 16 d, 20 d, 23 d and 25 d after model establishment. The levels of beta-endorphin (β-END), met-enkephalin (met-ENK), dynorphin A (Dyn A) were measured by radioimmunoassay; the mRNA expressions of mu opioid receptor (MOR), kappa opioid receptor (KOR) and delta opioid receptor (DOR) in synovial tissues of CIA rats were detected by I quantitative polymerase chain reaction (qPCR).</p><p><b>RESULTS</b>Compared with the control group, threshold of pain was reduced (all P<0. 01), arthritis index was increased (all P<0. 01) and paw swelling was increased (all P<0. 01) in the model group on the 16th day, 20th day, 23rd day, 25th day after model establishment. Compared with the model group, the threshold of pain was increased in the EA group (all P<0. 01), arthritis index and paw swelling were reduced (all P<0. 01) on the 23rd day and 25th day after model establishment. Compared with the control group, the level of Dyn A in synovial tissues of CIA rats was increased in the model group (P<0. 01); the mRNA expressions of MOR, KOR and DOR were down-regulated lower than 0. 5 fold of normal level. Compared with the model group, the level of β-END in synovial tissues of the knee joint was increased in the EA group (P<0. 05), and the mRNA expressions of MOR, KOR and DOR in synovial tissues of CIA rats were up-regulated more than 2 folds of normal level.</p><p><b>CONCLUSION</b>The intervention of EA on chronic pain of CIA rats is superior, which is likely to be related with effects of EA on anti-inflammation and up-regulation of synovial tissue β-END and MOR, KOR, DOR.</p>
Subject(s)
Animals , Cattle , Humans , Male , Rats , Acupuncture Analgesia , Acupuncture Points , Analgesics, Opioid , Allergy and Immunology , Arthritis, Rheumatoid , Allergy and Immunology , Therapeutics , Chronic Pain , Allergy and Immunology , Therapeutics , Dynorphins , Genetics , Allergy and Immunology , Electroacupuncture , Enkephalin, Methionine , Genetics , Allergy and Immunology , Rats, Wistar , Receptors, Opioid, mu , Genetics , Allergy and Immunology , Synovial Fluid , Allergy and Immunology , beta-Endorphin , Genetics , Allergy and ImmunologyABSTRACT
@#Objective To investigate the effect of electroacupuncture with low frequency on pain sensitization of neuropathic pain rats,and the possible mechanism of regulating peripheral pain sensitization. Methods Rat neuropathic pain model was established with the right L5 spinal nerve ligation. Zusanli (ST36) and Kunlun (BL60) were selected for electroacupuncture intervention. Mechanical allodynia, and the levels of stransient receptor potential vanilloid type 1 (TRPV1) and substance P (SP) in ipsilateral L5 and L4 dorsal root ganglion (DRG) were tested. A further validation experiment with TRPV1 agonist 6'-IRTX was carried out. Results Rats suffered from L5 spinal nerve ligation showed obvious pain sensitization. The levels of TRPV1 in ipsilateral L4 DRG and SP in ipsilateral L5 DRG were significantly elevated.Electroacupuncture with low frequency significantly relieved pain sensitization, and suppressed TRPV1 and SP increase. 6'-IRTX intraperitoneally administered significantly counteracted the anti-pain sensitization action of electroacupuncture with low frequency. Conclusion Electroacupuncture with low frequency is effective on neuropathic pain by intervening pain sensitization, which may be related to the regulation of DRG TRPV1 and SP.