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递到视锥双极细胞。据报道，AII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）在AII无长突细胞中产生的动作电位的详细特性，（2）在AII无长突细胞中Na电流的定位，以及（3）在视网膜中Nav亚基的定位。我们得到了以下结果。（1）（Tamalu & Watanabe）动作电位的频率1）根据局部施加到视杆双极细胞的树突的谷氨酸的浓度而降低，2）根据局部施加到AII无长突细胞的树状树突的谷氨酸的浓度而增加，3）根据注入索马的电流的强度而增加。（2）TTX局部作用于小叶附属器和索马对Na电流的抑制作用最强，而作用于树型树突的抑制作用最弱。因此，Nav可能主要分布在小叶附件周围，电压依赖性Ca通道主要位于小叶附件周围。此外，我们还发现钙电流的激活电压与动作电位的电压范围一致。（3）（Kaneko，Arita & Nakahira）原位杂交（ISH）实验表明，Nav1.1定位于内核层和内网层之间具有索马胞体的细胞中。抗小清蛋白抗体的双重染色结论：（1）光强度由动作电位频率编码，（2）AII无长突细胞表达的Nav亚型为Nav 1.1，（3）Nav定位于输出突触周围，以及（4）在输出突触周围产生动作电位并促进电压依赖性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。