The involvement of mu opioid receptorin peripheral regulation of chronic inflammatory pain induced by CFAin rats / 中国比较医学杂志

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 .