小鼠视网膜双极细胞的瞬时钙电流
Transient calcium current of retinal bipolar cells of the mouse.
作者信息
Kaneko A, Pinto L H, Tachibana M
机构信息
National Institute for Physiological Sciences, Okazaki, Japan.
出版信息
J Physiol. 1989 Mar;410:613-29. doi: 10.1113/jphysiol.1989.sp017551.
Abstract
- Isolated bipolar cells were obtained by enzymic (papain) dissociation of the adult mouse retina. The membrane voltage was clamped and the membrane currents were measured by the whole-cell version of the patch-clamp technique. Isolated bipolar cells and horizontal cells of the goldfish retina were also studied for comparison. 2. Hyperpolarization from the holding voltage, Vh, of -46 mV evoked a slowly activating, Cs+-sensitive, inward current (probably an h-current), and depolarization evoked a TEA- and Cs+-sensitive outward current (probably a combination of K+ currents). 3. Depolarization from a more negative Vh (e.g. -96 mV) evoked a transient inward current that had maximal amplitude between -40 and -20 mV. This current was identified as a Ca2+ current (ICa): its amplitude was increased with elevated [Ca2+]o and was decreased with reduced [Ca2+]o, and it was blocked by 4 mM-Co2+, but not by 5 microM-TTX. 4. Both the perikaryon and the axon terminal generated ICa with similar properties. 5. The plot of Ca2+ conductance (gCa) against membrane voltage (activation curve) was sigmoidal: in 10 mM [Ca2+]o, gCa increased for membrane voltages more positive than -65 mV, was half-maximal at about -25 mV, and reached saturation at about +30 mV. The plot of inactivation of gCa against membrane voltage was also sigmoidal: with 1 s conditioning depolarization in 10 mM [Ca2+]o, gCa decreased for membrane voltages more positive than -80 mV, was half-maximal at about -50 mV, and was fully suppressed for voltages greater than -30 mV. 6. ICa in the mouse bipolar cells was insensitive to 50 microM-Cd2+, 10 microM-nifedipine and 10 microM-Bay K 8644. In contrast, the calcium currents of bipolar and horizontal cells of the goldfish retina were markedly suppressed by 50 microM-Cd2+ and 10 microM-nifedipine, and were augmented several fold by 10 microM-Bay K 8644. The calcium currents of goldfish bipolar and horizontal cells were sustained, and were activated in a more positive range of potentials than the ICa of mouse bipolar cells. 7. The voltage range at which the ICa of mouse bipolar cells is activated includes the presumed range of membrane potentials spanned during light-evoked responses; thus, this current may participate in synaptic transmission. The transient character of ICa may also help to shape transient responses of ganglion cells.
摘要
- 通过成年小鼠视网膜的酶（木瓜蛋白酶）解离获得分离的双极细胞。膜电压被钳制，膜电流通过膜片钳技术的全细胞模式进行测量。还对金鱼视网膜的分离双极细胞和水平细胞进行了研究以作比较。2. 从 -46 mV 的钳制电压 Vh 进行超极化会诱发一种缓慢激活、对 Cs⁺ 敏感的内向电流（可能是 h 电流），去极化会诱发一种对 TEA 和 Cs⁺ 敏感的外向电流（可能是 K⁺ 电流的组合）。3. 从更负的 Vh（例如 -96 mV）进行去极化会诱发一种瞬时内向电流，其最大幅度在 -40 至 -20 mV 之间。该电流被鉴定为 Ca²⁺ 电流（ICa）：其幅度随着 [Ca²⁺]o 的升高而增加，随着 [Ca²⁺]o 的降低而降低，并且被 4 mM - Co²⁺ 阻断，但不被 5 μM - TTX 阻断。4. 胞体和轴突末梢都产生具有相似特性的 ICa。5. Ca²⁺ 电导（gCa）相对于膜电压的曲线（激活曲线）呈 S 形：在 10 mM [Ca²⁺]o 中，对于比 -65 mV 更正的膜电压，gCa 增加，在约 -25 mV 时达到半最大值，在约 +30 mV 时达到饱和。gCa 失活相对于膜电压的曲线也呈 S 形：在 10 mM [Ca²⁺]o 中进行 1 s 的条件性去极化，对于比 -80 mV 更正的膜电压，gCa 降低，在约 -50 mV 时达到半最大值，对于大于 -30 mV 的电压完全被抑制。6. 小鼠双极细胞中的 ICa 对 50 μM - Cd²⁺、10 μM - 硝苯地平及 10 μM - Bay K 8644 不敏感。相比之下金鱼视网膜双极细胞和水平细胞的钙电流被 50 μM - Cd²⁺ 和 10 μM - 硝苯地平显著抑制，并且被 10 μM - Bay K 8644 增强数倍。金鱼双极细胞和水平细胞的钙电流是持续的，并且在比小鼠双极细胞的 ICa 更正的电位范围内被激活。7. 小鼠双极细胞 ICa 被激活的电压范围包括光诱发反应期间假定的膜电位范围；因此，该电流可能参与突触传递。ICa 的瞬时特性也可能有助于塑造神经节细胞的瞬时反应。
Zotero 插件