- 學位論文
興奮性突觸在小鼠視網膜節細胞上之空間分布
Spatial Distribution of Excitatory Synapses in Mouse Retinal Ganglion Cells
摘要
視網膜節細胞以興奮性突觸接受雙極細胞訊號刺激，調控本身之生理特性。本篇 研究將帶有PSD95-GFP 之質體隨機轉染至小鼠視網膜節細胞中，使特定節細胞 樹突上的興奮性突觸位置表現綠色螢光蛋白，藉此分析各種形態之視網膜節細胞 上的興奮性突觸空間分布情形。本篇研究發現，儘管視網膜節細胞的大小形態各 異，但興奮性突觸在節細胞中的分布卻有一定的規律可循：（1）在一維的樹突 結構上，興奮性突觸的主要間隔為1-2 μm。這代表在一定的作用範圍內，空間 中的任一突觸的產生會降低其他突觸同時出現在此區域的機率。（2）對於形態不 同的節細胞而言，興奮性突觸在二維空間上的分布卻非常相似。興奮性突觸在初 級樹突結構上數量極少，但隨著與細胞本體的距離增加，突觸密度也隨之上升， 並在樹突末端達到最高值。基於以上的定量分析，本篇研究提供了小鼠視網膜節 細胞上興奮性突觸與樹突結構之關連性，這項研究將有助於瞭解興奮性突觸在空 間上的分布會如何影響細胞的生理反應。
並列摘要
Excitatory glutamatergic inputs from bipolar cells in part define the physiological properties of retinal ganglion cells. In this study, we investigate the distribution of excitatory synapses on various types of mouse retinal ganglion cells, by randomly transfecting cells with PSD95-GFP plasmids. Despite wide variation in the size and morphology of retinal ganglion cells, the expression of PSD95 puncta follows two general rules: (1) The PSD95 puncta are regularly spaced, in 1-2 μm interval, on local dendritic segments. Thus, the presence of an excitatory synapse creates an exclusion zone that rules out the presence of other synaptic inputs. (2) The spatial distribution of PSD95 puncta in a two-dimensional space is similar for most cell types. The excitatory synapses on primary dendrites are much less, and the density of excitatory inputs peaks at the edge of cell’s dendritic field. Mapping the distribution of synapses on retinal ganglion cells provides explicit structure information that facilitates the understanding of how distribution and localization of excitatory inhibitory inputs shape neuron’s responses.