Alteration of TRPM8 in Dorsal Root Ganglion in Rat Model of Neuropathic Pain / 天津医药

ABSTRACT

Objective: To investigate the changes of TRPM8 expression in dorsal root ganglion(DRG) in the rat model of chronic constriction injury(CCI) of the sciatic nerve. Methods: Seventy-two male SD rats weighing 250~280 g were randomly divided into 2 groups (n = 36 each) group I (CCI) and group II (sham operation). The threshold of cold hyperalgesia, heat hyperalgesia and mechanical hyperalgesia were measured before operation (baseline) and at 1, 4, 7, 10 and 14 d after operation. Six rats were killed at each time point in each group. The L5 DRGs ipsilateral to nerve injury were dissected out for determination of transient receptor potential melastatin 8(TRPM8) by immunohistochemical assay. Results: The thresholds of cold, thermal and mechanical stimuli started to decrease at 4 d after CCI in operation group and maintained at a relatively low level until the end of experiment. The cold and thermal hyperalgesia peaked at 10 d after operation and mechanical hyperalgesia at 14 d. Immunohistochemical assay demonstrated that expression of TRPM8 were increased in L5DRG on the operated side significantly at 4 d after CCI and reached the peak at 10 d and was maintained at a high level until the end of experiment. Conclusion: The upregulation of TRPM8 in DRG involved in the mechanism of neuropathic pain.