Changes in expression of TRPV1 in dorsal root ganglions during remifentanil-induced hyperalgesia in rats with incisional pain

Abstract

Objective To evaluate the changes in the expression of transient receptor potential vanilloid l (TRPV1) in dorsal root ganglions (DRGs) during remifentanil-induced hyperalgesia in the rats with incisional pain. Methods Thirty-two SPF healthy male Sprague-Dawley rats, weighing 240-260 g, aged 2-3 months, in which caudal catheters were successfully implanted, were divided into 4 groups (n=8 each) using a random number table: control group (group C), incisional pain group (group I), remifentanil group (group R), and incisional pain + remifentanil group (group I+ R). A 1 cm longitudinal incision was made through skin, fascia and muscle of the plantar aspect of the left hindpaw to establish the model of incisional pain.In group R, remifentanil was intravenously infused for 60 min at a rate of 1.2 μg·kg-1·min-1.In group I, the model of incisional pain was established, and the equal volume of normal saline was intravenously infused for 60 min at the same time.In group I+ R, the model of incisional pain was established, and remifentanil was intravenously infused for 60 min at a rate of 1.2 μg·kg-1·min-1 at the same time.In group C, the equal volume of normal saline was intravenously infused for 60 min.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawl latency (TWL) were measured at 24 h before normal saline or remifentanil infusion (T0) and 2, 6, 24 and 48 h after the end of infusion (T1-4). The rats were sacrificed after the last measurement of pain threshold, and the DRGs of the lumbar segment (L4-6) were removed for determination of the expression of TRPV1 protein and mRNA by Western blot and real-time polymerase chain reaction, respectively. Results Compared with group C, the MWT was significantly decreased, and the TWL was shortened at T1-4, and the expression of TRPV1 protein and mRNA was up-regulated in R, I and I+ R groups (P<0.05). Compared with group R or group I, the MWT was significantly decreased, and the TWL was shortened at T1-4, and the expression of TRPV1 protein and mRNA was up-regulated in group I+ R (P<0.05) Conclusion Up-regulated expression of TRPV1 in DRGs may be involved in the mechanism underlying remifentanil-induced hyperalgesia in the rats with incisional pain. Key words: TRPV cation channels; Piperidines; Hyperalgesia; Ganglia, spinal