Changes in expression of GluR1-containing AMPA receptor and GluR2-containing AMPA receptor in spinal dorsal horn in a rat model of incisional pain-remifentanil-induced hyperalgesia

Abstract

Objective To investigate the changes in the expression of GluR1-containing AMPA receptor and GluR2-containing AMPA receptor in spinal dorsal horn in a rat model of incisional pain-remifentanil-induced hyperalgesia.Methods Thirty-two male Sprague-Dawley rats,aged 2-3 months,weighing 240-260 g,in which the catheter was successfully inserted into the caudal vein,were randomly divided into 4 groups (n =8 each):control gourp (group C),remifentanil group (group R),incisional pain group (group P),and remifentanil + incisional pain group (group R + I).A 1-cm longitudinal incision was made through skin,fascia and muscle of the plantar aspect of the left hindpaw in chloral hydrate-anesthetized rats.Remifentanil 1.0 μg· kg-1 · min-1 was infused intravenously for 1 h sarting from beginning of establishment of incisional pain model.Paw withdrawal threshold (PWT) to yon Frey hair stimulation and paw withdrawal latency (PWL) to thermal stimulation were measured before remifentanil infusion and at 2,6,24 and 48 h after remifentanil infusion.The rats were sacrificed after the last behavioral test and L4-6 segments of the spinal cord were removed for determination of the expression of AMPA receptor GluR1 and GluR2 subunits in total and membrane protein in the dorsal horn of spinal cord by Western blot.The ratio between the expression of GluR1 and GluR2 subunits in membrane protein (GluR1/GluR2) was calculated.Results Compared with group C,PWL was significantly shortened,PWT was decreased,the expression of GluR1 in total and membrane protein was up-regulated,the expression of GluR2 in total and membrane protein was down-regulated,and GluR1/GluR2 ratio was increased in I,R and R + I groups (P ＜ 0.05).Compared with R and I groups,PWL was significantly shortened,PWT was decreased,the expression of GluR1 in total and membrane protein was up-regulated,the expression of GluR2 in total and membrane protein was down-regulated,and GluR1/GluR2 ratio was increased in group R + I (P ＜ 0.01).Conclusion Increased percentage of GluR1-conraining AMPA receptors in membrane protein induced by up-regulation of expression of GluR1-containing AMPA receptor and down-regulation of expression of GluR2-containing AMPA receptor in total and membrane protein is involved in the development of incisional pain-remifentanil-induced hyperalgesia in rats. Key words: Receptors, AMPA; Piperidines; Hyperalgesia; Pain; Spinal cord