Objective: To investigate the expression changes of metabotropic glutamate receptor 5 (mGluR5) in neuropathic pain.
Methods: Eighty-four adult male Sprague Dawley rats weighing 180-220 g were randomly divided into 7 groups (n = 12) : control group; S3, S7, and S14 groups: rats received the sham operation, the mechanical pain threshold was measured, and then the rats were decapitated and the ipsilateral lumbar spinal cord dorsal horn and dorsal root ganglion (DRG) samples were obtained on the 3rd, 7th, 14th postoperative day, respectively; C3, C7, and C14 groups: the chronic sciatic nerve constriction (CCI) model was established, the mechanical pain threshold was measured and the samples were obtained on the 3rd, 7th, 14th postoperative day, respectively. The expression level of mGluR5 mRNA and protein in the spinal cord and DRG were measured using the reverse transcriptase polymerase chain reaction and Western blot.
Results: In the CCI group, the mechanical pain threshold in each observation day was significantly lower than in the sham operation group (P < 0.05). In the spinal cord, the expressions of mGluR5 mRNA and protein were significantly elevated in the C3 group than in the S3 and the control group (P < 0.05). On the 7th and the 14th postoperative day, no significant difference was found in the expression of mGluR5 mRNA and protein between CCI groups and the sham operation groups or the control group. No change was detected in DRG mRNA or protein.
Conclusion: mGluR5 is differentially expressed in spinal cord in response to neuropathic pain, which suggests that mGluR5 may be involved in the mechanism of neuropathic pain.