Department of Biology, Animal Physiology, FAU Erlangen-Nürnberg, 91058, Erlangen, Germany.
Department of Biology, Animal Physiology, FAU Erlangen-Nürnberg, 91058, Erlangen, Germany.
Exp Eye Res. 2020 Jun;195:108028. doi: 10.1016/j.exer.2020.108028. Epub 2020 Apr 8.
Expression patterns of voltage-gated ion channels determine the spatio-temporal dynamics of ion currents that supply excitable neurons in developing tissue with proper electrophysiological properties. The purpose of the study was to identify fast cationic inward currents in mouse retinal horizontal cells (HCs) and describe their biophysical properties at different developmental stages. We also aimed to reveal their physiological role in shaping light responses (LRs) in adult HCs. HCs were recorded in horizontal slices of wild-type mouse retina at postnatal stages ranging from p8 through p60. Voltage-dependent inward currents were isolated with appropriate voltage protocols and blockers specific for sodium and T-type calcium channels. LRs were evoked with full-field flashes (130 μW/cm). Transient and steady inward currents were identified at all developmental stages. Transient currents were mediated by T-type calcium and TTX-sensitive sodium channels, whereas steady currents were blocked by cadmium, indicating the presence of high voltage-activated calcium channels. Activation and steady-state inactivation kinetics of T-type calcium channels revealed a contribution to the resting membrane potential during postnatal development. Additionally, both sodium and T-type calcium channels had an impact on HC LRs at light offset in adult animals. Our results showed that the voltage-dependent inward currents of postnatally developing mouse HCs consist of T-type calcium, TTX-sensitive sodium, and high voltage-activated calcium channels, and that transient ionic currents contributed to light-evoked responses of adult HCs, suggesting a role in HC information processing.
电压门控离子通道的表达模式决定了离子电流的时空动态，这些电流为发育组织中的兴奋性神经元提供适当的电生理特性。本研究的目的是鉴定小鼠视网膜水平细胞（HCs）中的快速阳离子内向电流，并描述它们在不同发育阶段的生物物理特性。我们还旨在揭示它们在成年 HCs 光反应（LRs）形成中的生理作用。在 p8 至 p60 的出生后阶段，在野生型小鼠视网膜的水平切片中记录 HCs。使用适当的电压方案和针对钠和 T 型钙通道的特异性阻断剂分离电压依赖性内向电流。使用全视野闪光（130 μW/cm）诱发 LRs。在所有发育阶段都鉴定出瞬态和稳态内向电流。瞬态电流由 T 型钙和 TTX 敏感的钠通道介导，而稳态电流被镉阻断，表明存在高电压激活的钙通道。T 型钙通道的激活和稳态失活动力学表明，在出生后发育过程中，T 型钙通道对静息膜电位有一定的贡献。此外，钠和 T 型钙通道都对成年动物光关闭时的 HC LRs 有影响。我们的研究结果表明，出生后发育的小鼠 HCs 的电压依赖性内向电流由 T 型钙、TTX 敏感的钠和高电压激活的钙通道组成，瞬态离子电流有助于成年 HCs 的光诱反应，表明其在 HC 信息处理中具有一定作用。
