兔视网膜方向选择性神经节细胞树突的独特分枝模式及其生理意义

本实验研究了兔视网膜中的方向选择性神经节细胞 (direction selective retinal ganglion cells,DS cells)树突野的分枝模式。测量了视网膜中方向选择性神经节细胞和作为经典分枝模式神经元代表的α神经节细胞的树突直径。发现 ,方向选择性神经节细胞的树突在分枝后直径达到 0 .5 μm,进一步分枝树突直径仍保持在 0 .5 μm左右 ,这样 ,在方向选择性神经节细胞树突野中大多数树突直径在 0 .5μm左右。而作为经典分枝模式神经元代表的α神经元的树突每次分枝后都逐级变细 ,最终直径达到 0 .5μm左右 ,这样 ,α神经节细胞的树突直径大部分都大于 0 .5μm。我们应用程序“NEU RON”对在两种神经元模型中 ,抑制点落于兴奋点与胞体之间 (proximal)和抑制点不落于兴奋点与胞体之间 (distal)这两种情况进行模拟。我们发现 ,当抑制点不落于兴奋点与胞体之间时 ,在方向选择性神经节细胞的树突分枝模型中 ,抑制效果更强。那么 ,将使得方向选择性神经节细胞对抑制点落于兴奋点和胞体之间的要求变得不是那么迫切。所以 ,方向选择性神经节细胞的这种独特分枝模式 ,也许可以避免或至少减轻其在发育中可能会产生的连线的复杂性。并且 ,我们对得出的结论进行了电路分析 ,对方向选择性神经节细胞这种独特的分枝模式具有的?

THE PHYSIOLOGICAL SIGNIFICANCE OF RABBIT DIRECTION SELECTIVE RETINAL GANGLION CELLS BRANCHING PATTERN PROPERTIES

In this project, the branching pattern of rabbit direction selective retinal ganglion cells (DS cells)was studied, and the diameters of the dendrites of the DS cells and α cells, which are the representatives of classical branching neurons, were measured. It was confirmed that the most dendrites of the DS cells retain similar diameter after branching while dendrites of the α cells became thinner after branching. The diameters of most dendrites in DS cells were 0.5 μm or so, while the diameters of most dendrites in α cells were larger than 0.5 μm. The effectiveness of proximal and distal inhibition on different morphologies was compared using a computer simulation program ‘Neuron’. It was found that the proximal inhibition is equally effective on both morphologies, whereas the distal inhibition was much more effective on the morphology of the DS cell. The results indicate that the unique morphology of the DS cells alleviates the demand for strict spatial relationship and therefore may simplify the wiring. The DS cells acquire a way to relieve the putative trouble during development. The electrical analysis gives a simple explanation to the conclusion we got.