Effects Of Ginsenoside-Rd On The Allodynia And The Expression Of Glutamate And NR2A/B In The Spinal Cord Dorsal Horn Of Rats With SNI

Ginsenoside-Rd (G-Rd) is a monosomic compound, extracted from the rare traditional Chinese medicine notoginseng , and is a new-style neuroprotective medicine. Recently, there has been accumulated evidence that it can not only selectively block receptor-operated Ca2+ channels, but also produce other actions, such as inhibition of Glutamate,s release, antioxidation, protection of mitochodria, ect. Moreover, glutamate and NMDA receptor are closely related to the development and modulation of neuropathic pain, so it suggests that G-Rd is possibly a potential analgesic. The aim of this study is to explore the effect and mechanisms of the analgesis of G-Rd on neuropathic pain.First, we observed the effect of G-Rd on the allodynia induced by constructing SNI pain model, and measured the change of the paw withdrawal mechanical thresholds (PWMT) before and after drug administration. At 10 d after SNI, the mean PWMT value on SNI side revealed clearly lower than that of control and sham operation groups, at 20 d the mean PWMT value dropped to the lowest. In SNI + G-Rd group, the mean PWMT value significantly ascended than that of SNI + saline group.Secondly, by using immunofluorescent staining, we observed the effect of G-Rd on the expression of glutamate and N-methyl-D-aspartale receptor-2-A/B subuni(tNR2A/B)in the corresponding spinal cord dorsal horn. The results revealed that the mean immunofluorescent intensity (MFI) of glutamate-like and NR2A/B subunit-like immunoreactive substances in the dorsal horn of the SNI side of the corresponding spinal segment showed significantly higher compared with that of control and sham operation groups. In SNI + G-Rd group, the MFI of glutamate-like immunoreactive substance revealed clearly lower than that of SNI and SNI + saline groups, however, the MFI of NR2A/B subunit-like immunoreactive substance did not showed significant changes in three groups mentioned above.In conclusion, this study demonstrated that G-Rd possessed obvious analgesic effect on neuropathic pain induced by SNI and the descent of the glutamate content in corresponding lumbal dorsal horn was a possible mechanism of its analgesic effect. These findings laid certain theoretical basis for the clinical analgesic application of G-Rd.