MODEL OF NERVE FIBER REGENERATION IN CNS BY EXCIMER LASER

准分子激光的特点是能够利用光化学效应切割组织，而不会对周围环境造成任何变形或危险的热损伤。这一事实表明激光切割的组织可能很容易修复。我们应用准分子激光切割脊髓，观察激光切割后的脊髓背索是否比刀切或冷冻损伤的脊髓修复得更好。此外，我们还制作了一个引导系统，将激光束引导到解剖显微镜，以便在直接观察的情况下切割微小区域。激光器为k - f激光器，波长为248nm。每脉冲能量密度为30 mJ/脉冲，脉冲频率为5 Hz × 1秒，照射面积为16mm × 0.2mm。因此，单位面积的能量密度为4.69J/cm^2。病灶深度约100mm。神经纤维被切断得很厉害。与病变相邻区域的神经胶质细胞和髓鞘严重受损。损伤后3-28天观察修复过程。病变后约1周，病变区域可见无髓鞘轴突、生长锥、胶质细胞和雪旺细胞。轴突后来被髓鞘包围。病变处形成了许多血管。研制了准分子激光制导系统。我们用它在解剖显微镜下切割狭窄的小区域。准分子激光的导引系统虽然有许多有待改进的地方，但被认为是一种很有前途的中枢神经系统再生实验模型。

Excimer laser is characterized by being able to cut the tissue by photochemical effect without giving any destortions or hazardous thermal damages to the surroundings. This fact indicates that the laser-cut tissuemight be readily repaired.We applied excimer laser to cut the spinal cord in order to examine whether the laser-cut dorsal funiculus can be repaired much better than the spinal cord injured by knife or freezing. In addition, we made a guide system which conducts the laser beam to the dissecting microscope for cutting minute areas under direct observations.The laser is Kr-F laser with the wave length of 248 nm. The energy density per pulse, pulse frequency and irradiation area are 30 mJ/pulse, 5 Hz x 1 sec, 16mm x 0.2mm, respectively. Therefore, the energy density per area is 4.69J/cm^2. The depth of the lesion was about 100mum.Nerve fibers are cut sharply. Glia cells and myelin sheaths are severely damaged in the area adjacent to the lesion. The repair processes are observed during 3-28 days post-lesion. About 1 week post-lesion, non-myelinated axons, growth cones, glia cells and Schwann cells are found in the areas of lesion. Axons are later surrounded by myelin sheaths. Many blood vessels are formed in the lesion.The guide system of excimer laser was made. We are using it to cut confined small areas under dissecting microscope. Altough there are many points to be improved, the guide system of excimer laser is considered to be promising for the experimental model of CNS regeneration.