Abstract:

Objective To investigate the effects of group Ⅲ metabotropic glutamate receptors(mGluRs) subtypes on neuropathic pain. Methods Thirty SD rats were randomly divided into five groups (n=6), and received a single intrathecal injection of 10 μL saline, L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4), VU0155041, AMN082 and (S)-3,4-Dicarboxyphenylglycine (DCPG) respectively on the fifth day after intrathecal catheterization. Values of 50% paw withdrawal threshold (50%PWT) and paw withdrawal latency (PWL) were measured every 15 min and 30 min after drugs administration respectively. Another thirty SD rats were randomly divided into five groups (n=6), and received a single intrathecal injection of 10 μL saline and ditto drugs respectively on the seventh day after spinal nerve ligation (SNL) surgery and intrathecal catheterization. Values of 50%PWT and PWL were measured as the ditto methods after drugs administration. Another eighteen SD rats were randomly divided into blank control group, SNL group and SNL+injection group(saline, VU0155041, AMN082 and DCPG)(n=3), all rats were taken the spinal cord at the lumbar enlargement 30 min after injection, and the expression of mGluR4, mGluR7 and mGluR8 was determined by Western blotting. Results L-AP4, VU0155041, AMN082 and DCPG had no influence on the normal rats (P>0.05), while had different analgesic effects on rats with neuropathic pain (P<0.05), in which VU0155041 had the most significant effect. The expression of mGluR4 in spinal cord in SNL group was significantly lower than that in blank control group (P<0.05), and the expression of mGluR4 in injection groups was significantly higher than that in saline group (P<0.05). There was no significant difference in the expression of mGluR7 among groups (P>0.05), and mGluR8 was hardly expressed in the spinal cord. Conclusion mGluR4 is the main subtype of group Ⅲ mGluRs involved in the regulation of neuropathic pain.

Key words: group Ⅲ metabotropic glutamate receptor, metabotropic glutamate receptor 4, neuropathic pain