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.