Control of intracellular chloride concentration and GABA response polarity in rat retinal ON bipolar cells
Control of intracellular chloride concentration and GABA response polarity in rat retinal ON bipolar cells
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DOI：
10.1113/jphysiol.2002.024877
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发表时间：
2002-11-15
影响因子：
5.5
通讯作者：
Attwell, D
中科院分区：
文献类型：
--
作者：
Billups, D;Attwell, D
gaba能调节视网膜双极细胞在早期视觉加工中起重要作用。它有助于形成中心环绕的接受野，在视网膜外的双极细胞树突上对视觉信号进行空间过滤，并在视网膜内的双极细胞突触终端上产生时间过滤。在ON双极细胞中观察到的氯转运体分布被预测会产生细胞内氯浓度[Cl(-)](i)，其在树突中的浓度明显高于在突触末端的浓度。这将允许树突gaba门控的Cl（-）通道产生去极化，形成细胞接受野的横向抑制包围所需要的，而突触末端gaba门控的Cl（-）通道产生光响应的时间形成所需要的超极化。与这一观点相反，我们在这里表明，在ON双极细胞中，[Cl(-)](i)在树突中的含量仅略高于突触末端，并且树突中的gaba门控通道可能产生超极化而不是去极化。我们还发现，除了转运体外，[Cl(-)](i)还受Cl（-）通过离子通道的运动控制，[K(+)](o)的变化改变了[Cl(-)](i)，双极细胞中[Cl(-)](i)的电压依赖平衡将在照明引起的膜电位变化后产生时间依赖的gaba能调节适应，时间常数为8 s。[Cl(-)](i)对视网膜双极细胞电压变化的时间依赖性适应，可能会在信号通过视网膜时增加一个以前未被怀疑的时间处理层。
GABAergic modulation of retinal bipolar cells plays a crucial role in early visual processing. It helps to form centre-surround receptive fields which filter the visual signal spatially at the bipolar cell dendrites in the outer retina, and it produces temporal filtering at the bipolar cell synaptic terminals in the inner retina. The observed chloride transporter distribution in ON bipolar cells has been predicted to produce an intracellular chloride concentration, [Cl(-)](i), that is significantly higher in the dendrites than in the synaptic terminals. This would allow dendritic GABA-gated Cl(-) channels to generate the depolarization needed for forming the lateral inhibitory surround of the cell's receptive field, while synaptic terminal GABA-gated Cl(-) channels generate the hyperpolarization needed for temporal shaping of the light response. In contrast to this idea, we show here that in ON bipolar cells [Cl(-)](i) is only slightly higher in the dendrites than in the synaptic terminals, and that GABA-gated channels in the dendrites may generate a hyperpolarization rather than a depolarization. We also show that [Cl(-)](i) is controlled by movement of Cl(-) through ion channels in addition to transporters, that changes of [K(+)](o) alter [Cl(-)](i) and that voltage-dependent equilibration of [Cl(-)](i) in bipolar cells will produce a time-dependent adaptation of GABAergic modulation with a time constant of 8 s after illumination-evoked changes of membrane potential. Time-dependent adaptation of [Cl(-)](i) to voltage changes in retinal bipolar cells may add a previously unsuspected layer of temporal processing to signals as they pass through the retina.