Targeting P2X7 receptor for the treatment of central post-stroke pain in a rodent model

• Rat central post-stroke pain (CPSP) model as a promising animal model for investigating pathogenesis mechanism.
• Significant involvements of ATP receptor P2X7 and its downstream affecting cytokine IL-1β in rat CPSP.
• Effectiveness of targeting P2X7 receptor and IL-1β in CPSP rats.
• Therapeutic potentials of utilizing P2X7 as drug target in treatment of hemorrhage stroke and its CPSP symptom.

Stroke is a leading cause of death and disability in industrialized countries. Approximately 8–14% of stroke survivors suffer from central post-stroke pain (CPSP) when hemorrhagic stroke occurs in lateral thalamic regions, which severely affects their quality of life. Because the mechanisms of CPSP are not well understood, effective treatments have not been developed. In the present study, we tested the hypothesis that persistent CPSP is caused by P2X7 receptor activation after brain tissue damage and subsequent elevations in inflammatory cytokines. A thalamic hemorrhagic rat model was used, characterized by thermal and mechanical allodynia that develops in the subacute to chronic phases upon CPSP onset. We found a significant increase in P2X7 expression in reactive microglia/macrophages in thalamic peri-lesion tissues at 5 weeks post-hemorrhage. Thalamic P2X7 receptors were directly involved in pain transmission and hypersensitivity. The systemic targeting of P2X7 receptors during the acute stage of hemorrhage rescued abnormal pain behaviors and neuronal activity in the thalamocingulate pathway by reducing reactive microglia/macrophage aggregation and associated inflammatory cytokines. After CPSP onset, the targeting of interleukin-1β reversed abnormal pain sensitivity. The aberrant spontaneous thalamocortical oscillations in rats with CPSP were modulated by blocking P2X7 receptors. Taken together, our results suggest that targeting P2X7 may be bi-effective in the treatment of CPSP, as both a pain blocker and immunosuppressant that inhibits inflammatory damage to brain tissue. P2X7 receptors may serve as a potential target to prevent the occurrence of CPSP and may be beneficial for the recovery of patients from stroke.

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