Changes in expression of artemin in skin around incision during remifentanil-induced hyperalgesia in rats with incisional pain

Objective To evaluate the changes in the expression of artemin in skin around the incision during remifentanil-induced hyperalgesia in the rats with incisional pain. Methods Thirty-two healthy male Sprague-Dawley rats, aged 10-12 weeks, weighing 250-280 g, 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 plus remifentanil group (group I+ R). Remifentanil was intravenously infused for 60 min at a rate of 1 μg·kg-1·min-1 in group R. In group I, the model of incisional pain was established, and the equal volume of normal saline was infused for 60 min via the tail vein at the same time.In group I+ R, the model of incisional pain was established, and remifentanil was infused for 60 min via the tail vein at a rate of 1 μg·kg-1·min-1 at the same time.The equal volume of normal saline was infused for 60 min via the tail vein in group C. Mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 24 h before infusion of remifentanil or normal saline and 2, 6, 24 and 48 h after the end of infusion (T0-4). Rats were sacrificed following the last measurement of pain threshold, and ipsilateral plantar skin was removed for detection of the expression of artemin protein and mRNA (by fluorescent quantitative real-time polymerase chain reaction or Western blot). Results Compared with group C, MWT was significantly decreased and TWL was shorten at T1-4, and the expression of artemin protein and mRNA in plantar skin was up-regulated in R, I and I+ R groups (P<0.01). Compared with R and I groups, MWT was significantly decreased and TWL was shorten at T1-4, and the expression of artemin protein and mRNA in plantar skin was up-regulated in group I+ R (P<0.01). Conclusion The peripheral mechanism by which remifentanil induces hyperalgesia may be related to up-regulated expression of artemin in skin around the incision in the rats with incisional pain. Key words: Piperidines; Pain, postoperative; Hyperalgesia; Ganglia, spinal; Glial cell line-derived neurotrophic factor