Activation of P2X4 receptors in midbrain cerebrospinal fluid-contacting nucleus leads to mechanical hyperalgesia in chronic constriction injury rats.

Neuropathic pain is a refractory pain state, and its mechanism is still not clear. Previous studies have shown that the purine receptor P2X4R expressed on hyperactive microglia in the spinal cord is essential for the occurrence and development of neuropathic pain. The cerebrospinal fluid-contacting nucleus (CSF-contacting nucleus) in the midbrain has been found to play an important role in the descending inhibition system of modulation. However, there have been no studies on P2X4R in the CSF-contacting nucleus involved in neuropathic pain. To investigate whether P2X4R is expressed in the CSF-contacting nucleus and whether its expression in the CSF-contacting nucleus is involved in the regulation of neuropathic pain, we used a model of chronic sciatic nerve ligation injury (CCI) to simulate neuropathic pain conditions. Immunohistochemistry experiments were conducted to identify the expression of P2X4R in the CSF-contacting nuclei in CCI rats, and western blot analysis showed a significant increase in P2X4R levels 7 days after modeling. Then, we packaged a P2rx4 gene-targeting shRNA in scAAV9 to knock down the P2X4R level in the CSF-contacting nucleus, and we found that CCI-induced mechanical hyperalgesia was reversed. In conclusion, P2X4R expressed in the CSF-contacting nucleus is involved in the process of neuropathic pain, and downregulating P2X4R protein in the CSF-contacting nucleus can reverse the occurrence and development of hyperalgesia, which could represent a potent therapeutic strategy for neuropathic pain.