Changes in expression of PICK1 in spinal cord and dorsal root ganglion neurons during remifentanil-induced hyperalgesia in rats with incisional pain

Objective To evaluate the changes in the expression of protein interacting with Cα kinase 1 (PICK1) in the spinal cord and dorsal root ganglion (DRG) neurons during remifentanil-induced hyperalgesia in rats with incisional pain. Methods Thirty-two male Sprague-Dawley rats, weighing 240-260 g, aged 42-49 days, were randomly 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 remifentanil + incisional pain group (group R + I). In R and R+ I groups, remifentanil was infused intravenously for 60 min at the rate of 1.2 μg· kg-1·min-1.In C and I groups, normal saline was infused intravenously for 60 min at the rate of 0.12 ml·kg-1·min-1.In I and R+ I groups, the model of incisional pain was established, and remifentanil and normal saline were infused intravenously, respectively, at the same time.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured before normal saline or remifentanil infusion, and at 2, 6, 24, and 48 h after the end of normal saline or remifentanil infusion (T1-4). The rats were sacrificed after the last measurement of pain threshold.The lumbar segment (L4-6) of the spinal cord and left DRGs were removed for determination of the expression of PICK1 mRNA (by quantitative real-time reverse transcriptase-polymerase chain reaction) and PICK1 protein (by Western blot). Results Compared with group C, the MWT was significantly decreased, the TWL was shortened, and the expression of PICK1 protein and mRNA was up-regulated in R and R+ I groups, and the MWT was significantly decreased, the TWL was shortened (P 0.05). Compared with group I, the MWT was significantly decreased, the TWL was shortened, and the expression of PICK1 protein and mRNA was up-regulated in group R+ I (P 0.05). Conclusion The mechanism by which remifentanil induces hyperalgesia may be related to up-regulation of PICK1 expression in the spinal cord and DRG neurons of rats with incisional pain. Key words: Protein kinase C-alpha; Piperidines; Pain, postoperative; Hyperalgesia; Spinal cord; Ganglia, spinal; Neurons