光刺激通過光感受器中的光轉導信號來抑制視網膜暗電流。視網膜電圖（Electroretinography (ERG)）雖可檢測暗電流的堵塞 （視網膜電圖a-波）。然而，標準視網膜電圖代表了視網膜神經的綜合平均活動信號，不能得到個別或局部功能區域的信息。在這項研究中，我們使用了多電極陣列系統（Med-64），并直接記錄了視網膜光感受器活動。視網膜從黑暗適應的嚙齒動物分離出來，玻璃體面覆蓋在電極陣列上。經光刺激后，負波被每個電極記錄下來。 結果 ： 加入氨基丁酸 （乃一種表達于ON-雙極細胞mGluR6的選擇性激動劑）后并沒有阻止負電流的反應產生。反應力度大小隨著視網膜發展而增加。當視網膜局部受傷，光引起的反應只是在受傷的視網膜區域減少。本實驗也測試了從大鼠分離出來并經MNU（N-methyl-N-nitrosourea）處理的視網膜。在經MNU處理的大鼠視網膜的中央位置，反應隨著MNU注射逐漸減弱。與此相反，在視網膜周邊位置，反應的力度卻保留，跟從免疫組化實驗對視網膜厚度的觀測一致。結論是，視網膜之光誘發反應可用Med-64記錄。Med-64系統有利于檢測不起眼但重要的局部光感受器活動。這些二維信息于臨床領域及視網膜功能恢復研究十分重要 （例如基因轉移或細胞移植等方面）。

Detection of localized retinal malfunction in retinal degeneration model using a multielectrode array system.

Homma K, Osakada F, Hirami Y, Jin ZB, Mandai M, Takahashi M.

Laboratory for Retinal Regeneration, Center for Developmental Biology, RIKEN, Chou-ku, Kobe, Japan.

Light stimulation inhibits the retinal dark current through phototransduction signals in the photoreceptors. Electroretinography (ERG) detects the blockage of the dark current as the a-wave of the ERG. However, standard ERGs represent the summed neural activity of the retina, and information on localized functions cannot be obtained. In this study, we used a multielectrode array (MEA) system and directly recorded the focal activities of the photoreceptors of the retina. Retinas were isolated from dark-adapted rodents and were draped over the electrode array with vitreal surface of the retina on the electrode array. After light stimulation, negative waves were recorded from each electrode. Adding aminobutyric acid, a selective agonist of mGluR6 expressed on ON-bipolar cells, to the media did not block the generation of the responses. The amplitude of the response increased with increasing retinal development. When the retina was locally injured, light-elicited responses were diminished only in the injured areas of the retina. Retinas isolated from rats given N-methyl-N-nitrosourea (MNU) were also tested. In central retinas of MNU-treated rats, the responses were progressively decreased following injection of MNU. In contrast, in the peripheral retinas, amplitude of the responses was relatively retained, consistent with the retinal thickness observed by immunohistochemistry. In conclusion, light-evoked responses were recorded with the MEA system. The MEA system was useful for detecting subtle and focal activation of photoreceptors. This spatial information should be valuable in investigating local functional recovery in therapeutically treated areas, such as in gene transfer or cell transplantation. (c) 2009 Wiley-Liss, Inc.

文章來源：http://www.ncbi.nlm.nih.gov/pubmed/19224574?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_
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