In the retina, ON- and OFF-type bipolar cells are classified by subtype-specific center responses, which are attributed to differences in glutamate receptor subtypes. However, the mechanisms by which ON- and OFF-type bipolar cells generate subtype-specific surround responses remain unclear. One hypothesis for surround responses is that intracellular Cl concentrations ([Cl-]_i) are set at different levels to achieve opposite polarities for GABA responses in ON- and OFF-type bipolar cells. Although this hypothesis is supported by previous findings obtained from rod (ON-) type bipolar cells, there is currently no information on OFF-type bipolar cells. In the present study, we examined the distribution and function of the Cl transporters, the Na-K-Cl co-transporter (NKCC1) and K-Cl co-transporter (KCC2), in rod (ON-) and OFF-type bipolar cells using immunohistochemical, in situ hybridization, and electrophysiological methods. Rod (ON-) and OFF-type bipolar cells both expressed NKCC1 and KCC2. However, the functional contribution of NKCC1 and KCC2 to the regulation of [Cl⁻]_i differed between rod (ON-) and OFF-type bipolar cells. Strong NKCC1 activity increased [Cl⁻]_i in rod (ON-) type bipolar cells, while that of KCC2 decreased [Cl⁻]_i in OFF-type bipolar cells. We also confirmed the presence of a [Cl⁻]_i gradient between dendrites and axon terminals in rod (ON-type) bipolar cells. Thus, the subtype-specific control of [Cl⁻]_i is achieved by the activity of NKCC1 relative to that of KCC2 and appears to influence the polarity of surround responses.

在视网膜中，ON型和OFF型双极型细胞通过亚型特异性中心反应进行分类，这归因于谷氨酸受体亚型的差异。但是，ON和OFF型双极细胞产生亚型特异性周围反应的机制仍不清楚。环绕声响应的一种假设是细胞内Cl浓度（[Cl-] _i将）设置为不同的水平，以在ON型和OFF型双极细胞中实现GABA反应的相反极性。尽管从棒状（ON-）型双极型电池获得的先前发现支持了这一假设，但目前尚无关于OFF型双极型电池的信息。在本研究中，我们研究了杆（ON-）和OFF型双极中Cl转运蛋白，Na-K-Cl协同转运蛋白（NKCC1）和K-Cl协同转运蛋白（KCC2）的分布和功能细胞使用免疫组织化学，原位杂交和电生理方法。杆状（ON-）和OFF型双极细胞均表达NKCC1和KCC2。然而，NKCC1和KCC2的到的调节功能的贡献[氯^- ]_我棒型（ON-）和OFF型双极型电池之间的区别。强NKCC1活性增加[氯^- ]_我在杆（ON-）型双极细胞，而KCC2的下降[氯^- ]_我在OFF型双极细胞。我们还证实的存在[氯^- ]_我在杆（ON型）双极细胞梯度树突和轴突终端之间。因此，的亚型特异性控制[氯^- ]_我是通过相对于KCC2的NKCC1的活性来实现，并似乎影响的环绕响应的极性。