Abstract

The effects of puerarin on acute nociception mediated by the P2X₃ receptor in rat dorsal root ganglia (DRG) were studied. Intrathecal injection of adenosine triphosphate (ATP) or α,β-methylene-ATP (α,β-meATP) could potentiate acute nociceptive responses induced by intraplantar injection of ATP or α,β-meATP in rat hindpaw. Intraplantar injection of formalin increased the expression of P2X₃ in rat DRG and induced acute nociceptive responses. These induced nociceptive responses were inhibited by intrathecal injection of puerarin, which also decreased the up-regulated expression of P2X₃ mRNA and protein in DRG induced by intraplantar injection of formalin. Molecular docking studies revealed that puerarin could interact perfectly with homology-modeled rat P2X₃ receptor (rP2X₃). rP2X₃ can be restricted to binding ATP because of its combination with puerarin (increasing the concentration of free ATP), therefore blocking the rP2X₃ channel. Whole cell patch clamp recording showed that puerarin inhibited the potentiation of P2X₃ receptor-mediated currents induced by lipopolysaccharide. These results demonstrated that puerarin inhibited nociceptive responses induced by ATP, α,β-meATP, or formalin and its inhibitory effect was mediated by reduction of inflammatory pain-induced up-regulation of P2X₃ receptor expression and blockade of ATP binding sites on the P2X₃ receptor. Our results suggest that puerarin could decrease acute pain mediated by the P2X₃ receptor in the DRG.

Key words: Puerarin, acute nociceptive response, P2X₃ receptor, dorsal root ganglia, whole cell patch clamp.