Functional significance of localization of the Na channel in retinal A2 amacrine cells

视网膜A2无长突细胞Na通道定位的功能意义

• 批准号: 15500289
• 负责人: WATANABE Shu-ichi
• 金额: $ 2.18万
• 依托单位: Saitama Medical School
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15500289/
• 关键词: retina; AII amacrine cell; action potential; voltage-dependent Na channel; messenger RNA; glutamate; localization; parvalbumin; paravalbumin; アマクリン細胞; イオンチャネル; 視覚; 神経回路網; 杆体経路; パッチクランプ法; 免疫組織化学

Retinal AII amacrine cells transmit light information from rod bipolar cells to cone bipolar cells. It has been reported that AII amacrine cells generate action potentials of 10-20 mV in amplitude. In the present research, we elucidated (1)detailed properties of action potentials generated in the AII amacrine cell, (2)localization of the Na current within the AII amacrine cell, and (3)localization of Nav subunit within the retina. We obtained following results.(1)(by Tamalu & Watanabe) Frequency of the action potential was 1)decreased depending on the concentration of glutamate locally applied to the dendrite of the rod bipolar cells, 2)increased depending on the concentration of glutamate locally applied to the arboreal dendrites of the AII amacrine cell, 3)increased depending on the intensity of injected current into the soma.(2)(by Tamalu) TTX locally applied to the lobular appendage and soma most strongly inhibited the Na current compared to the application to the arboreal dendrite. Therefore, Nav may distribute mainly around the lobular appendage where voltage-dependent Ca channels are mostly localized. Also we found that activation voltage of the Ca current coincides with voltage range of the action potential.(3)(by Kaneko, Arita & Nakahira) In situ hybridization (ISH) experiments revealed that Nav 1.1 were localized in cells that had the soma on the border between the inner nuclear layer and inner plexiform layer. Double staining of antibodies against parvalbumin (a marker of the AII amacrine cell) and ISH showed that Nav 1.1 expressing cells were parvalbumin-immunopositive cells.In conclusion we found that (1)intensity of the light is coded by frequency of the action potential, that (2)Nav subtype expressed in the AII amacrine cell is Nav 1.1, that (3)Nav are localized around the output synapse, and that (4)the action potential is generated around the output synapse and facilitates activation of voltage-dependent Ca channels.

视网膜AII无长突细胞将光信息从视杆双极细胞传输到视锥双极细胞。据报道，所有无长突细胞产生幅度为 10-20 mV 的动作电位。在本研究中，我们阐明了（1）AII无长突细胞中产生的动作电位的详细特性，（2）AII无长突细胞内Na电流的定位，以及（3）视网膜内Nav亚基的定位。我们获得了以下结果。(1)（由 Tamalu 和 Watanabe）动作电位的频率 1) 根据局部施加到杆双极细胞树突的谷氨酸浓度而降低，2) 根据局部谷氨酸浓度而增加应用于 AII 无长突细胞的树状树突，3）根据注入体细胞的电流强度而增加。（2）（通过与应用于树栖树突相比，局部应用于小叶附属物和体细胞的 Tamalu) TTX 对 Na 电流的抑制最为强烈。因此，Nav 可能主要分布在小叶附件周围，其中电压依赖性 Ca 通道大多位于其中。我们还发现 Ca 电流的激活电压与动作电位的电压范围一致。(3)（作者：Kaneko、Arita 和 Nakahira）原位杂交 (ISH) 实验表明 Nav 1.1 位于具有体细胞的细胞中内核层和内丛状层之间的边界。针对小清蛋白（AII 无长突细胞的标记）的抗体和 ISH 的双重染色表明，表达 Nav 1.1 的细胞是小清蛋白免疫阳性细胞。 总之，我们发现（1）光的强度由动作电位的频率编码， (2)AII 无长突细胞中表达的 Nav 亚型是 Nav 1.1，(3)Nav 位于输出突触周围，并且 (4) 动作电位产生于输出突触周围，促进电压依赖性 Ca 通道的激活。

项目成果

Tamalu F, Nakahira K, Watanabe S-I: "Role of signal in signal processing of retinal AII amacrine cells"Japanese Journal of Physiology. Supplement(in press). (2004)

Tamalu F、Nakahira K、Watanabe S-I：“信号在视网膜 AII 无长突细胞信号处理中的作用”日本生理学杂志。

Arita K, Nakahira K, Watanabe S-I: "Voltage-dependent Na^+ channel immunoreactive processes in the inner plexiform layer of the retina"Japanese Journal of Physiology. Supplement(in press). (2004)

Arita K、Nakahira K、Watanabe S-I：“视网膜内丛状层中的电压依赖性 Na^2 通道免疫反应过程”日本生理学杂志。