Lee Sammy C S, Meyer Arndt, Schubert Timm, Hüser Laura, Dedek Karin, Haverkamp Silke
Max Planck Institute for Brain Research, 60438, Frankfurt am Main, Germany.
University of Sydney-Save Sight Institute, Sydney, New South Wales, 2000, Australia.
J Comp Neurol. 2015 Jul 1;523(10):1529-47. doi: 10.1002/cne.23752. Epub 2015 Mar 10.
Amacrine cells comprise ∼ 30 morphological types in the mammalian retina. The synaptic connectivity and function of a few γ-aminobutyric acid (GABA)ergic wide-field amacrine cells have recently been studied; however, with the exception of the rod pathway-specific AII amacrine cell, the connectivity of glycinergic small-field amacrine cells has not been investigated in the mouse retina. Here, we studied the morphology and connectivity pattern of the small-field A8 amacrine cell. A8 cells in mouse retina are bistratified with lobular processes in the ON sublamina and arboreal dendrites in the OFF sublamina of the inner plexiform layer. The distinct bistratified morphology was first visible at postnatal day 8, reaching the adult shape at P13, around eye opening. The connectivity of A8 cells to bipolar cells and ganglion cells was studied by double and triple immunolabeling experiments by using various cell markers combined with synaptic markers. Our data suggest that A8 amacrine cells receive glutamatergic input from both OFF and ON cone bipolar cells. Furthermore, A8 cells are coupled to ON cone bipolar cells by gap junctions, and provide inhibitory input via glycine receptor (GlyR) subunit α1 to OFF cone bipolar cells and to ON A-type ganglion cells. Measurements of spontaneous glycinergic postsynaptic currents and GlyR immunolabeling revealed that A8 cells express GlyRs containing the α2 subunit. The results show that the bistratified A8 cell makes very similar synaptic contacts with cone bipolar cells as the rod pathway-specific AII amacrine cell. However, unlike AII cells, A8 amacrine cells provide glycinergic input to ON A-type ganglion cells.
无长突细胞在哺乳动物视网膜中约有30种形态类型。最近对一些γ-氨基丁酸（GABA）能宽视野无长突细胞的突触连接和功能进行了研究；然而，除了视杆通路特异性AII无长突细胞外，甘氨酸能小视野无长突细胞在小鼠视网膜中的连接情况尚未得到研究。在这里，我们研究了小视野A8无长突细胞的形态和连接模式。小鼠视网膜中的A8细胞呈双分层，在内网状层的ON亚层有小叶状突起，在OFF亚层有树状树突。这种独特的双分层形态在出生后第8天首次可见，在出生后第13天（约睁眼时）达到成年形态。通过使用各种细胞标记物与突触标记物相结合的双重和三重免疫标记实验，研究了A8细胞与双极细胞和神经节细胞的连接情况。我们的数据表明，A8无长突细胞从OFF和ON视锥双极细胞接收谷氨酸能输入。此外，A8细胞通过缝隙连接与ON视锥双极细胞相连，并通过甘氨酸受体（GlyR）亚基α1向OFF视锥双极细胞和ON A型神经节细胞提供抑制性输入。对自发甘氨酸能突触后电流的测量和GlyR免疫标记显示，A8细胞表达含有α2亚基的GlyR。结果表明，双分层的A8细胞与视锥双极细胞形成的突触联系与视杆通路特异性AII无长突细胞非常相似。然而，与AII细胞不同的是，A8无长突细胞向ON A型神经节细胞提供甘氨酸能输入。
