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Updated: Jun 5, 2026
Electrophysiological Methods to Assess Peripheral Pain Block in an Anesthetized Rat
Published on: November 21, 2025
[The effect of formalin-induced pain on CCK in rat spinal cord neurons]
Li Li1, Hong-an Li, Jin-fang Jiang
1Department of Physiology, Shihezi University Medical College, Shihezi 832002, China.
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 (P <0.01). 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 (P < 0.01). 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 (P < 0.01).
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.
