Role of puerarin in the signalling of neuropathic pain mediated by P2X3 receptor of dorsal root ganglion neurons.

Tissue injury or inflammation of the nervous system may result in chronic neuropathic pain characterized by sensitivity to painful stimuli. P2X(3) receptors play a crucial role in facilitating pain transmission. Puerarin is an active compound of a traditional Chinese medicine Ge-gen, and Ge-gen soup has anti-inflammatory effects. The present research investigated the role of puerarin in the signalling of chronic neuropathic pain mediated by P2X(3) receptors of rat dorsal root ganglion neurons. Chronic constriction injury (CCI) rat model was adopted. Sprague-Dawley rats were randomly divided into blank control group (Ctrl), sham group (Sham), puerarin-treated control group (Ctrl+PUE), chronic constriction injury (CCI) group and puerarin-treated CCI group (CCI+PUE). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured by the von-Frey test and the Hargreaves' test respectively. The stain values of P2X(3) protein and mRNA in L4/L5 dorsal root ganglion (DRG) were detected by immunohistochemistry, western blot and in situ hybridization. At day 4-7 after the operation of CCI rats, MWT and TWL in group CCI and CCI+PUE were lower than those in group Ctrl, Sham and Ctrl+PUE, while there was no difference among group Ctrl, Sham and Ctrl+PUE. At day 7-10 after operation, MWT and TWL in group CCI+PUE was higher than those in group CCI, but there was no significant difference between group CCI+PUE and group Ctrl (p>0.05). At day 14 after operation, the stain values of P2X(3) proteins and mRNAs in L4/L5 DRG of group CCI were higher than those in group Ctrl, Sham, Ctrl+PUE and CCI+PUE, while the stain values of P2X(3) proteins and mRNAs in group CCI+PUE were significantly decreased compared with those in group CCI. Therefore, puerarin may alleviate neuropathic pain mediated by P2X(3) receptors in dorsal root ganglion neurons.