Expression of cation-chloride cotransporters in the spinal cord of rat of incision model

Abstract

Objective To investigate the expression of sodium-potassium-chloride co-transporter 1 (NKCC 1) and potassiumchloride co-transporter 2 (KCC2) in the spinal dorsal horn and dorsal root ganglion (DRG) of the incisional rat.Methods Adult male Sprague-Dawley rats were randomly divided into 5 groups of 6,a control and 4 incision groups at 2 h,2 d,3 d,7 d following incision.Incision was made or only skin degerming under inhalation anesthesia.At the specific time,rats were perfused with fixative under anesthesia,then the L4-L5 spinal cord and bilateral L5 DRG removed,and NKCC1 and KCC2 expression estimated by immunohistochemistry.Results In the intact rats,NKCC1 was expressed in the DRG,and both NKCC1 and KCC2 was expressed in the dorsal horn with KCC2 predominated.NKCC 1 increased in the DRG (P=0.010) following incision.Compared to controls(18.0±2.8),the number of NKCC1-positive neurons was significantly higher in ipsilateral DRG on 2 h (40.7±2.0),2 d (54.7±9.8),3 d (45.3±8.6) following incision (P=0.026,0.001,0.008).NKCC1 also increased in the ipsilateral dorsal horn (P＜0.01),compared tocontrols (14.33±0.56),the number of NKCC1-positive neurons was significantly higher on 2 h (31.00±1.32),2 d (50.33± 1.80),3 d(38.67±3.04),7 d (32.33±0.21) and all P＜0.01.KCC2 decreased in the dorsal horn following incision (P<0.01).Compared to controls(42.7±2.6),the number of KCC2-positive neurons was significantly lower in the dorsal horn on 2 h(18.0±3.5),2 d(18.0±1.7),3 d(23.3±1.5) and 7 d (24.7±1.1) following incision (all P＜0.01).Conclusions NKCC1 increased in the DRG and dorsal horn while KCC2 decreased in the dorsal horn in the incision model of rat,which suggested that NKCC1 and KCC2 participated in the mechanism of hyperalgesia following incision. Key words: Sodium-potassium-chloride co-transporter 1 ; Potassium-chloride co-transporter 2; Postoperative pain; Hyperalgesia