| Objective To study the effects on MK-801 on apoptosis after acute spinal cord injury, the rat model of acute SCI which received peritoneal injection of MK-801 as a non competitive NMDA receptor antagon were divided into the test group. The apoptosis of the test group was measured by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) methods. The expression of C-Fos gene and Caspase-3 gene were detected immunohistochemically.Methods 30 cleanliness standard SD rats were divided into three groups at random, including sham group, SCI group and MK-801 group. Each group contains 10 rats. Sham group was only treated with laminectomy. Two other groups suffered spinal cord injury according to Allen's weight-drop method. 5 ml/kg of saline was delivered to SCI group in 30 minutes after injury. MK-801 group received the same volume of MK-801 reagents. Sham group had not dealt with. At the time point of 24 hours, each rat was sacrificed to obtain the whole spinal cord tissue from T10 segment with microinstruments for making paraffin sections which were prepared for the test of TUNEL methods and immunohistochemical stain to assay protein FOS and protein Caspase-3. The positive reactions of the test of TUNEL methods and immunoreaction of C-Fos gene and Caspase-3 gene were observed by optical microscope. The statistically significant among three groups were analyzed in order to investigate the influence of MK-801 on apoptosis.Results (1) In 24 hours after injury, it was greatly shown in the gray matter and white matter of spinal cord of SCI group that hemorrhage, edema, inflammatory cell infiltrate, degeneration and necrosis of neurons and several gaps surrounding survival neurons. MK-801 group showed less hemorrhage, less edema, less gliosis and more survival neurons than SCI group.(2)The results of TUNEL methods: Many positive cells were found in both SCI group and MK-801 group, but nothing could be found in sham group. The positive neurons were mainly found in the inner part of dorsal horn and partly found encircling the central canal. The typical image of a positive cell is the nuclear chromatins shrank into brown objects en plaque converging by the nuclear membrane. The three groups have distinctive statistical difference. The number of the positive cells in SCI group was much more than one in MK-801 group. The number of the positive cells in MK-801 group was more than one in sham group. (3)The results of immunoreaction of Caspase-3 gene and C-Fos gene: Brown particles can be found in the cytoplasm of the positive cells existing in gray matter neurons and gray matter and white matter neuroglial cells. Where the positive cells showed is approximately similar with that in TUNEL methods. The statistical result of three groups are identical.Conclusion Apoptosis of neural cells was the mainly way of neural cells death after secondary spinal cord injury. There were positive expression of C-Fos gene and Caspase-3 gene the apoptosis correlates after SCI. MK-801 could inhibit the expressions of both genes and decrease the amount of apoptotic cells to protect the neurons. The study could provide some theoretical basis for treating SCI.
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