Objective To evaluate the changes in mRNA expressions of Toll-like receptor 4 (TLR4) and its down-stream cytokines IL-1β,IL-6 and TNF-a in incisional tissues from a rat with postoperative pain.Methods Incisional pain was induced in 74 male adult SD rats weighing 200-250 g.Paw mechanical withdrawal threshold (PMWT) around the wound on the operated and nonoperated sides was measured at 1 day before operation and at 0.5,1,2,6 and 12 hours as well as 1,2,3,5 and 7 days after operation.Skin incisional tissues were removed for determination of mRNA expressions of TLR4,IL-1β,IL-6 and TNF-a using real-time quantitative PCR at 1 day before operation and at 2 and 8 hours as well as 1,2,3,5 and 7 days after operation.Results Compared with the baseline value before operation,PMWT on the operated side was significantly decreased at 0.5 hours-5 days after operation,mRNA expression of TLR4 around the wounds on the operated side was down-regulated at 2 hours after operation followed by a gradual increase,mRNA expressions of IL-1β,IL-6 and TNF-α on the operative side were up-regulated at 2 and 8 hours as well as 1,2,3 and 5 days after operation (P ＜ 0.05),but no significant changes were found in PMWT and mRNA expressions of TLR4,IL-1β,IL-6 and TNF-α on the non-operated side(P ＞ 0.05).PMWT on the operated side was lowest at 6 hours after operation followed by the gradual increase,mRNA expression of TLR4 on the operated side peaked at 2 days after operation,and mRNA expressions of IL-1β,IL-6 and TNF-a respectively peaked at 2 hours,1 day and 3 days after operation (P ＜ 0.05).mRNA expressions of TLR4,IL-1β,IL-6 and TNF-a were negatively correlated with PMWT on the operative side (r =-0.501,-0.743,-0.893,-0.657,P ＜ 0.05),and mRNA expressions of IL-1 β,IL-6 and TNF-a were positively correlated with the level of TLR4 mRNA(r=0.764,0.283,0.667,P＜0.05).Conclusion mRNA expressions of TLR4 and its down-stream cytokines IL-1 β,IL-6 and TNF-a in skin incisional tissues are up-regulated,which may be involved in the development and maintenance of postoperative pain.

Objective To evaluate the role of C-X-C chemokine receptor type 4 ( CXCR4) in the dorsal root ganglia ( DRG) in incisional pain in rats. Methods Thirty-two male Sprague-Dawley rats, aged 7-10 weeks, weighing 250-300 g, in which intrathecal catheters were successfully implanted, were divided into 4 groups (n＝8 each) using a random number table method: sham operation group (group S), CXCR4 antagonist AMD3100 plus sham operation group (group A+S), incisional pain group (group I) and CXCR4 antagonist AMD3100 plus incisional pain group (group A+I). Rats were anesthetized with sevoflu-rane. AMD3100 20 μg (in 10 μl of normal saline) was intrathecally injected, and no incision was made 30 min later in group A+S. A 1-cm longitudinal incision was made through skin, fascia and muscle of the plantar aspect of the left hindpaw in group I. AMD3100 20 μg (in 10 μl of normal saline) was intrathecally injected, and 30 min later the model of incisional pain was established in group A+I. The mechanical paw withdrawal threshold ( MWT) and thermal paw withdrawal latency ( TWL) were measured at 24 h before surgery and 2, 4, 8, 16 and 24 h after surgery. The rats were sacrificed after the last measurement of pain threshold and the DRGs of the lumbar segment (L4-6) were removed for detecting the expression of CXCR4, phosphorylated extracellular regulated protein kinase ( p-ERK) and total ERK ( t-ERK) by Western blot. Results Compared with group S, MWT was significantly decreased and TWL was shortened at T1-5in group I and group A+I, and the expression of CXCR4 and p-ERK in DRGs was significantly up-regulated (P＜0. 05), and no significant change was found in the expression of t-ERK in group I, no significant change was found in the expression of CXCR4, p-ERK and t-ERK in group A+I, and no significant change was found in the parameters mentioned above in group A+S (P＞0. 05). Compared with group I, MWT was significantly increased and TWL was prolonged at T1-5, the expression of CXCR4 and p-ERK in DRGs was down-regulated (P＜0. 05), and no significant change was found in the expression of t-ERK in group A+I (P＞0. 05). Conclusion CXCR4 in DRGs is involved in incisional pain, and the mechanism may be re-lated to activating ERK1∕2 signaling pathway in rats.