ABSTRACT
Objective To observe the distribution and possible mechanism of P2X7R in periaq-ueductal gray matter (PAG)in a rat model with chronic neuropathic pain in vivo.Methods The in-trathecal catheterization and sciatic nerve injury (SNI)were performed.All animals were randomly assigned into 3 groups with 26 rats in each,which was group Sham,control group (group C)and brilliant blue G (BBG)group (group BBG),respectively.Normal saline or BBG 10 μl were intrathe-cally injected after SNI and repeated for seven days.Paw-withdrawal mechanical thresholds (PWT) were measured on day 0,day 7,day 14,and day 21 after SNI.The rats were sacrificed and PAG tis-sues were collected on day 14 and day 21,separately.The distributions of P2X7R were observed by immunofluorescence.The protein contents of P2X7R and GFAP were assessed by Western blot assays.Results The P2X7R was expressed in PAG in rats.The PWTs of the control group showed a significant decrease during the 21-day period compared with the sham group.The P2X7R signals were predominantly expressed in astrocytes in PAG after SNI.Both P2X7R and GFAP expression remark-ably increased.Administration of BBG increased the PWTs,and inhibited the P2X7R and GFAP ex-pressions compared with those atthe same point of time of the control group.Conclusion These results indicated that P2X7R in PAG might participate in nociception modulation in the midbrain in chronic neuropathic pain.