The influence of ketamine on KCC2 in spinal cord of rat in remifentanil-induced hyperalgesia

Abstract

Objective To explore the effect of pre-treatment of subcutaneous injection of ketamine on remifentanil induced hyperalgesia and K+ /Cl-cotransporter 2, KCC2) expression on spinal cord of rats. Methods 60 male adult SD rats were randomly divided into five groups(n=12 in each group): control group (group C), the incision group(group I), the incision plus remifentanil group(group I+ R), the incision plus ketamine group(group I+ K) and the incision plus remifentanil and ketamine group(group I+ R+ K). Mechanical withdrawal threshold (MWT) was evaluated at 24 hours before incision(T0), 2 hours, 6 hours, 24 hours and 48 hours after incision(T1~T4). The lumbar spinal cords of rats were taken out at T4 time point and the KCC2 detected was detected by immunofluorescence analysis and western blot analysis. Results Compared with group C(T1(14.5±1.7)g, T2(14.2±1.1)g, T3(13.9±1.8)g, T4(14.2±1.1)g), MWT of other groups at T1 (I(5.6±0.8)g, I+ R(3.2±1.0)g, I+ K(6.8±1.7)g, I+ R+ K(5.1±1.6)g), T2 (I(6.9±1.0)g, I+ R(4.3±1.2)g, I+ K(8.0±1.4)g, I+ R+ K(6.2±1.5)g), T3 (I(7.6±0.9)g, I+ R(5.4±1.1)g, I+ K(10.3±1.2)g, I+ R+ K(7.1±1.1)g), T4 (I(8.9±1.1)g, I+ R(7.5±1.4)g, I+ K(11.3±1.2)g, I+ R+ K(8.3±1.2)g)and the expression of KCC2 at T4 decreased (P<0.05). Compared with group I(T1(5.6±0.8)g, T2(6.9±1.0)g, T3(7.6±0.9)g, T4(8.9±1.1)g), MWT of group I+ R (T1(3.2±1.0)g, T2(4.3±1.2)g, T3(5.4±1.1)g, T4(7.5±1.4)g) decreased at all time points after incision (T1~T4)(P<0.05) and the expression of KCC2 at T4 decreased significantly (P<0.05). Compared with group I(T1(5.6±0.8)g, T2(6.9±1.0)g, T3(7.6±0.9)g, T4(8.9±1.1)g), MWT of group I+ K (T1(6.8±1.7)g, T2(8.0±1.4)g, T3(10.3±1.2)g, T4(11.3±1.2)g) increased at all time points after incision (T1~T4)(P<0.05) and the expression of KCC2 at T4 increased (P<0.05). Compared with group I+ R(T1(3.2±1.0)g, T2(4.3±1.2)g, T3(5.4±1.1)g, T4(7.5±1.4)g), MWT of group I+ R+ K (T1(5.1±1.6)g, T2(6.2±1.5)g, T3(7.1±1.1)g, T4(8.3±1.2)g) increased at all time points after incision (T1~T4)(P<0.05) and the expression of KCC2 at T4 increased (P<0.05). Conclusion Pre-treatment of subcutaneous injection of ketamine can reduce the hyperalgesia of rats induced by remifentanil and reduce the inhibition of KCC2 expression on dorsal horn of spinal cord. Key words: Remifentanil; Hyperalgesia; Ketamine; KCC2