Gap junctions are ubiquitous within the retina, but in general, it remains to be determined whether gap junction coupling between specific cell types is sufficiently strong to mediate functionally relevant coupling via electrical synapses. From ultrastructural, tracer coupling and immunolabeling studies, there is clear evidence for gap junctions between cone bipolar cells, but it is not known if these gap junctions function as electrical synapses. Here, using whole-cell voltage-clamp recording in rat (male and female) retinal slices, we investigated whether the gap junctions of bipolar cells make a measurable contribution to the membrane properties of these cells. We measured the input resistance (RN) of bipolar cells before and after applying meclofenamic acid (MFA) to block gap junctions. In the presence of MFA, RN of ON-cone bipolar cells displayed a clear increase, paralleled by block of the electrical coupling between these cells and AII amacrine cells in recordings of coupled cell pairs. For OFF-cone and rod bipolar cells, RN did not increase in the presence of MFA. The results for rod bipolar cells are consistent with the lack of gap junctions in these cells. However, for OFF-cone bipolar cells, our results suggest that the morphologically identified gap junctions between these cells do not support a junctional conductance that is sufficient to mediate effective electrical coupling. Instead, these junctions might play a role in chemical and/or metabolic coupling between subcellular compartments.

中文翻译：

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间隙连接对大鼠视网膜开和关双极细胞膜特性的差异贡献。

间隙连接在视网膜内无处不在，但一般来说，特定细胞类型之间的间隙连接耦合是否足够强以通过电突触介导功能相关的耦合仍有待确定。从超微结构、示踪剂耦合和免疫标记研究来看，有明确的证据表明视锥双极细胞之间存在间隙连接，但尚不清楚这些间隙连接是否起到电突触的作用。在这里，我们利用大鼠（雄性和雌性）视网膜切片的全细胞电压钳记录，研究了双极细胞的间隙连接是否对这些细胞的膜特性做出了可测量的贡献。我们测量了应用甲氯芬那酸 (MFA) 阻断间隙连接之前和之后双极细胞的输入电阻 (RN)。在存在 MFA 的情况下，ON 锥体双极细胞的 RN 显示出明显的增加，同时在耦合细胞对的记录中这些细胞与所有无长突细胞之间的电耦合被阻断。对于离锥体和杆体双极细胞，RN 在 MFA 存在的情况下不会增加。杆状双极细胞的结果与这些细胞中缺乏间隙连接一致。然而，对于离锥双极细胞，我们的结果表明这些细胞之间形态学上识别的间隙连接不支持足以介导有效电耦合的连接电导。相反，这些连接可能在亚细胞区室之间的化学和/或代谢耦合中发挥作用。