Role of spinal P2Y1R in development of remifentanil-induced hyperalgesia in rats with incisional pain: relationship with function of NR1 and NR2B in spinal cord / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of spinal P2Y1R in the development of remifentanil-induced hyperalgesia in rats with incisional pain (IP) and the relationship with the function of NR1 and NR2B in spinal cord.Methods:Forty-eight healthy adult male Sprague-Dawley rats, aged 10-12 weeks, weighing 250-280 g, in which intrathecal catheters were successfully placed, were divided into 6 groups ( n=8 each) using a random number table method: control group (group C), P2Y1R antagonist MRS2179 group (group M), remifentanil group (group R), remifentanil plus MRS2179 group (group R+ M), IP plus remifentanil group (group I+ R) and IP plus remifentanil plus MRS2179 group (group I+ R+ M). In group C, normal saline 10 μl was intrathecally injected, and 10 min later normal saline was infused for 60 min via the tail vein at a rate of 0.1 ml·kg -1·min -1.In group M, MRS2179 0.6 nmol/kg was intrathecally injected, and 10 min later normal saline was infused for 60 min via the tail vein at a rate of 0.1 ml·kg -1·min -1.In group R, normal saline 10 μl was intrathecally injected, and 10 min later remifentanil was infused for 60 min via the tail vein at a rate of 1 μg·kg -1·min -1.In group R+ M, MRS2179 0.6 nmol/kg was intrathecally injected, and 10 min later remifentanil was infused for 60 min at a rate of 1 μg·kg -1·min -1 via the tail vein.In group I+ R, normal saline 10 μl was intrathecally injected, 10 min later remifentanil was infused for 60 min via the tail vein at a rate of 1 μg·kg -1·min -1, and IP was established at 10 min after onset of remifentanil infusion.In group I+ R+ M, MRS2179 0.6 nmol/kg was intrathecally injected, 10 min later remifentanil was infused via the tail vein for 60 min at a rate of 1 μg·kg -1·min -1, and IP was established at 10 min after onset of remifentanil infusion.The mechanical paw withdrawal threshold (MWT), thermal paw withdrawal latency (TWL), and the number of paw lifts on the cold plate were measured at 24 h before infusion of remifentanil or normal saline and at 2, 6, 24, and 48 h after the end of infusion.The animals were sacrificed after the last measurement of the pain threshold, L 4-6 segments of the spinal cord were removed for determination of the expression of P2Y1R, phosphorylated NR1 (p-NR1), NR1, phosphorylated NR2B (p-NR2B) and NR2B (by Western blot), for calculation of the ratios of p-NR1/NR1 and p-NR2B/NR2B, and for detection of expression of P2Y1R mRNA, NR1 mRNA and NR2B mRNA (by real-time polymerase chain reaction). Results:Compared with group C, MWT was significantly decreased, TWL was shortened, the number of paw lifts on the cold plate was increased, the expression of P2Y1R protein and mRNA, NR1 protein and mRNA, p-NR1, NR2B protein and mRNA and p-NR2B was up-regulated, and p-NR1/NR1 ratio and p-NR2B/NR2B ratio were increased in group R ( P<0.01). Compared with group R, MWT was significantly increased, TWL was prolonged, the number of paw lifts on the cold plate was decreased, the expression of P2Y1R, p-NR1, NR1 protein and mRNA, p-NR2B, NR2B protein and mRNA was down-regulated, and p-NR1/NR1 ratio and p-NR2B/NR2B ratio were decreased in group R+ M ( P<0.05 or 0.01). Compared with group I+ R, MWT was significantly increased, TWL was prolonged, the number of paw lifts on the cold plate was decreased, the expression of P2Y1R, p-NR1, NR1 protein and mRNA, p-NR2B, NR2B protein and mRNA was down-regulated, and p-NR1/NR1 ratio and p-NR2B/NR2B ratio were decreased in group I+ R+ M ( P<0.01). Conclusion:Spinal P2Y1R can enhance the function of NR1 and NR2B, which may be involved in the development of remifentanil-induced hyperalgesia in rats with IP.