ABSTRACT
Objective To investigate the relationship remifentanil-induced hyperalgesia and func-tion of nitrated glutamate transportor-1 ( GLT-1) and glutamine synthetase ( GS) in the spinal cord of rats with incisional pain. Methods Thirty-two male Sprague-Dawley rats, weighing 260-280 g, aged 2-3 months, in which caudal catheters were successfully implanted, were divided into 4 groups (n=8 each) u-sing a random number table method: control group ( group C) , incisional pain group ( group I) , remifen-tanil group ( group R) and remifentanil plus incisional pain group ( group RI) . Normal saline was intrave-nously infused for 60 min at 0. 1 ml · kg-1 · min-1 in group C. The model of incisional pain was estab-lished, and normal saline was simultaneously infused for 60 min via the tail vein at 0. 1 ml·kg-1 ·min-1 in group I. Remifentanil was infused for 60 min via the tail vein at 1. 0 μg· kg-1 ·min-1 in group R. The model of incisional pain was established, and remifentanil was infused for 60 min via the tail vein at 1. 0μg· kg-1 ·min-1 in group RI. The mechanical paw withdrawal threshold ( MWT) and thermal paw with-drawal latency ( TWL) were measured at 24 h before infusion of remifentanil or normal saline ( T0 ) and at 2, 6, 24 and 48 h after infusion ( T1-4 ) . The rats were sacrificed after the last measuremnet of pain thresh-old, and the L4-6 segment of the spinal cord was removed for determination of the expression of GLT-1 and GS (by Western blot) and expression of nitrated GLT-1 (nGLT-1) and nitrated GS (nGS) (by Western blot) . Ratios of nGLT-1∕GLT-1 and nGS∕GS were calculated. Results Compared with group C, the MWT was significantly decreased and TWL was shortened at T1-4 , the expression of GLT-1 and GS was down-regu-lated, the expression of nGLT-1 and nGS was up-regulated, and ratios of nGLT-1∕GLT-1 and nGS∕GS were increased in I, R and RI groups ( P<0. 05) . Compared with group I and group R, the MWT was signifi-cantly decreased and TWL was shortened at T1-4 , the expression of GLT-1 and GS was down-regulated, the expression of nGLT-1 and nGS was up-regulated, and ratios of nGLT-1∕GLT-1 and nGS∕GS were increased in group RI ( P<0. 05) . Conclusion The mechanism of remifentanil-induced hyperalgesia may be related to impaired function of GLT-1 and GS in the spinal cord of rats with incisional pain.
ABSTRACT
Objective To investigate the changes and their significance of glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) expressions in glial cells following spinal cord injury (SCI) in adult rats.Methods Twenty-five healthy female adult SD rats were randomly divided into control group (5 rats) and experimental group (20 rats).The contusive spinal cord injury models were prepared at T10 segment in the rats in the experimental group according to the modified Allen's method.At days 1,3,7 and 14 following SCI,five rats were sacrificed by cardiac perfusion and the spinal cord segments adjacent to the epicenter of injury were obtained at each time point after the neurological function of hind limbs was assessed using the modified Tarlov scale.Changes of GLAST and GLT-1 expressions were detected semi-quantitatively using immunofluorescence and computer image analysis system (IPP 6.0).Results (1) Single immunofluorescence:Moderate GLAST expression was found in the control group.The GLAST expression was increased slightly at day 1 after SCI,decreased progressively at days 3 and 7 after SCI,and increased slightly at day 14 after SCI.The GLAST expression in experimental group was significantly lower than those in control group at days 3,7 and 14 after SCI (P ＜ 0.05).Moderate GLT-1 expression was detected in the control group.The expression of GLT-1 was increased slightly at day 1 after SCI,decreased to the lowest at day 3 after SCI,and increased slightly at days 7 and 14 after SCI.The GLT-1 expression in experimental group was significantly lower than those in control group at days 3,7 and 14 after SCI (P ＜0.05).(2) Double immunofluorescence:GLAST expression was found on astrocytes in the control group.The GLAST expression in experimental group was decreased at day 1 after SCI,further decreased progressively at days 3 and 7 after SCI,and started to recover at day 14 after SCI.The coexpressions of GLAST and glial fibrillary acidic protein (GFAP) in experimental group were significantly lower than those in the control group at days 3 and 7 after SCI (P ＜ 0.05).The expression of GLAST was found on microglial cells in the control group.The expression of GLAST in experimental group was increased obviously at day 1 after SCI and increased progressively at days 3-14 after SCI.The coexpressions of GLAST and OX-42 in experimental group were significantly than those in the control group at days 3,7 and 14 after SCI (P ＜ 0.05).(3) Double immunofluorescence:GLT-1 expression was found on astrocytes in the control group.The GLT-1 expression was decreased at day 1 after SCI,further decreased progressively at days 3 and 7 after SCI,and started to recover at day 14 after SCI.The coexpressions of GLT-1 and GFAP were significantly lower than those in the control group at days 3 and 7 after SCI (P ＜ 0.05).The GLT-1 expression was found on microglial cells in the control group.The GLT-1 expression was increased obviously at day 1 after SCI and increased progressively at days 3-14 after SCI.The coexpressions of GLT-1 and OX-42 were significantly higher than those in the control group at days 1,3,7 and 14 after SCI (P ＜ 0.05).Conclusion The glutamate transporters GLAST and GLT-1 show different expression patterns in astrocytes and microglia following SCI in rats,which may be correlated with the roles of different glial cells in repair of spinal cord injury.