Objective To observe the effects of tetramethylpyrazine (TMP) on acute nociception in rat hindpaw induced by purine 2X (P2X) receptor agonists, such as adenosine triphosphate (ATP) and ?, ?-meATP, prostaglandin E 2 (PGE 2), and substance P (SP). Methods The effects of TMP administered intraplantarlly on the acute nociception induced by P2X receptor agonists, PGE 2, or SP in the rat hindpaw were investigated by the method of the behavioral study. Results TMP (10 mmol/L) significantly depressed the acute nociception induced by ATP (1 ?mol/L) or ?, ?-meATP (0.6 ?mol/L) in the rat hindpaw. TMP (10 mmol/L) could inhibit the acute nociception induced by PGE 2 (5 ?mol/L) or ?, ?-meATP (0.2 ?mol/L) coinjected with PGE 2 (5 ?mol/L). TMP (10 mmol/L) could not affect the acute nociception induced by ?, ?-meATP (0.2 ?mol/L) coinjected with SP (10 ?mol/L). TMP could not obviously affect the inflammatory edema in rat hindpaw induced by the local administration of PGE 2, SP, or ?, ?-meATP coinjected with PGE 2 or SP individually. Conclusion The antinociceptive effects of TMP may mainly be associated with inhibiting the transmission of nociceptive information mediated by P2X receptor activation.

Aim To investigate effects of tetramethylpyrazine (TMP) on neuropathic pain induced by P2X_3 receptor. Methods Chronic constriction injury (CCI) model was adopted. Mechanical withdrawal threshold and thermal withdrawal latency were measured and P2X_3 immunoreactivity in L_4/L_5 spinal cord was detected by immunohistochemistry. Results At day 14 after operation, the mechanical withdrawal threshold and thermal withdrawal latency in group Ⅴ(CCI group) were lower than those in groupⅠ(NS group),Ⅱ(TMP group),Ⅲ(sham group) and Ⅳ (CCI+ TMP group)(P0.05). The expression of P2X_3 receptor in L_4/L_5 spinal cord of group Ⅳ was lower than that of group Ⅴ (P