Changes of spinal G protein-coupled receptor kinase 2 (GRK2) expression in persistent postoperative pain in rats

Objective To investigate the change of spinal G protein-coupled receptor kinase 2 (GRK2) expression in persistent postoperative pain evoked by skin/muscle incision and retraction (SMIR) in rats. Methods 40 male Sprague Dawley (SD) rats were divided into 2 groups (n=20) using a random number table: sham operation group and skin/muscle incision and retraction group (SMIR group). A rat model of peristent postoperativepain evoked by SMIR was made according to the method described by Flatters. Pain behavior was assessed by paw mechanical withdrawal threshold (MWT) to von Frey filament stimulationintensity at 1 d before operation (T0) and 3 d (T1), 7 d (T2), 14 d (T3) and 21 d (T4) after operation. 4 rats in each group were sacrificed at T0-4, the L4-L6 segments of the spinal cord were obtained for determination of GRK2 expression in the spinal cord by Western blot. Results Compared with T0, the MWT was significantly decreased and the expression of spinal GRK2 was down-regulated at T1-T4 in SMIR group (P<0.05). Compared with sham operation group, the MWT and the expression of spinal GRK2 was decreased at T1-T4 in SMIR group (P<0.05). Conclusions The down-regulation of expression of spinal GRK2 may be involved in the development and maintenance of persistent postoperative pain in rats evoked by SMIR. Key words: Pain, postoperative/ME; Spinal cord/ME; G-protein-coupled receptor kinase 2/ME; Rats