[The effect of formalin-induced pain on CCK in rat spinal cord neurons].

Aim: CCK is one of the strongest endogenous anti-opioid substances and suppresses morphine tolerance which results from long term use of morphine.This study explores the modulatory effect of CCK on pain formalin-induced.Methods: The effect of formalin-induced pain on CCK immunoreactivity in rat sensory neurons was observed through immunohistochemistry technique.Results: After 1 h of subcutaneous injection of formalin in one paw of rats,the number of positive neurons of CCK immunoreactivity in spinal cord neurons was obviously increased and greater than that of non-injection side(P0.01).The semi-quantitative optical density average values of CCK immunoreactivity neurons were 0.397±0.014 and 0.295±0.007 in injection side and non-injection side respectively,the difference was obvious(P0.01).After 3 h of subcutaneous injection of formalin in one paw of rats,the semi-quantitative optical density average values of CCK immunoreactivity neurons were 0.366±0.009 and 0.303±0.005 in injection side and noninjection side respectively,the difference was significant(P0.01).Conclusion: Formalin-induced pain can significantly change semi-quantitative optical density average value of CCK immunoractivity in spinal cord neurons,this indicates CCK participates in modulation of pain.