General Physiology and Biophysics Revised manuscript #2 Title: Involvement of P2X7 receptors in satellite glial cells of dorsal root ganglia in the BmK I -induced pain model of rats Running title: P2X7R contributes to pain

37 The P2X7 receptor (P2X7R) plays an important role in inflammatory and 38 neuropathic pain. Our recent study indicated that activation of P2X7R in microglial 39 cells of spinal cord contributes to the inflammatory pain induced by BmK I,the major 40 active compound from Buthusmartensi Karsch (BmK). In the present study, we 41 further investigated whether P2X7R in satellite glial cells (SGCs) of dorsal root 42 ganglion (DRG) is involved in the BmK Iinduced pain in rats. The results found that 43 the expression of P2X7R in SGCs was increased in the ipsilateral side of L4–L5 44 DRGs after intraplantar injection of BmK I. Moreover, the expression of an 45 inflammatory cytokine IL-1β was increased in DRG after BmK I injection. Systemic 46 administration of an inhibitor of P2X7R (A-438079) significantly inhibited both 47 spontaneous and evoked nociceptive behaviors induced by BmK I. These results 48 suggest that the P2X7R in SGCs of DRG might contribute to pain induced by toxins 49 that sensitize peripheral sensory nerves. 50