Dopamine modulates S-potential amplitude and dye-coupling between external horizontal cells in carp retina
Dopamine modulates S-potential amplitude and dye-coupling between external horizontal cells in carp retina
复制标题
多巴胺调节鲤鱼视网膜外部水平细胞之间的 S 电位幅度和染料耦合
作者：
T. Teranishi;K. Negishi;S. Kato
鱼视网膜中的水平细胞是电偶联的，并具有缝隙连接1，2，因此在体内注射的染料通常可以自由扩散到相邻的细胞3-5。应用多巴胺(DA)改变了水平细胞对光的反应的空间特性，增加了明视L型S电位的幅度，但减少了它们的横向扩展6-8。这些效应被归因于DA对水平细胞膜电阻的作用，特别是在缝隙连接7，我们目前对鲤鱼视网膜的研究与这一点一致，表明DA也将细胞内的荧光黄(LY)限制为单个注入的水平细胞，这与DA对S电位的影响一样。它被多巴胺阻滞剂氟哌啶醇所拮抗。此外，我们提出的证据表明，鱼类中的多巴胺能网状细胞正常地调节水平细胞反应的空间特性，可能通过DA受体介导的机制作用于它们的连接阻力。用6-羟基多巴胺(6-OHDA)破坏网状细胞后，L型S反应向中心光的电位显著降低，但这些反应的侧向扩散更宽，而注入的染料则广泛扩散到邻近细胞。但在6-OHDA处理后，DA仍保持其正常活动，恢复幅度大、感受场窄的S电位，并将LY限制在注射细胞内，这两种作用均可被二丁酰环腺苷高度模拟。
Horizontal cells in the fish retina are electrically coupled and possess gap junctions1,2 so that intraceUularly injected dye normally diffuses freely to neighbouring cells3–5. Applied dopamine (DA) alters the spatial properties of the horizontal cell responses to light, increasing the amplitude of photopic L-type S-potentials but decreasing their lateral spread6–8. These effects have been attributed to the action of DA on horizontal cell membrane resistance, particularly at the gap junctions7, and our present study on the carp retina agrees with this in showing that DA also restricts intracellular Lucifer yellow (LY) to single injected horizontal cells, an effect, like those of DA on the S-potentials, which is antagonized by the dopamine blocker haloperidol. In addition, we present evidence that dopaminergic interplexiform cells in fish normally function to regulate the spatial properties of responses in horizontal cells, possibly acting on their junctional resistance via a DA-receptor-mediated mechanism. Previous destruction of the interplexiform cells with 6-hydroxydopamine (6-OHDA) resulted in much reduced L-type S-potentials to centred lights but wider lateral spread of these responses, while the dye injected spread extensively to neighbouring cells. After 6–OHDA treatment, however, applied DA retained its normal activity, restoring large-amplitude, narrow receptive-field S-potentials and restricting LY to the injected cells, effects which were both closely mimicked by dibutyryl cyclic AMP.