Stacy Rebecca Colleen, Wong Rachel Oi Lun
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Comp Neurol. 2003 Feb 3;456(2):154-66. doi: 10.1002/cne.10509.
Ganglion cells of the mammalian retina undergo structural remodeling before their dendrites are confined to functionally distinct laminas within the inner plexiform layer. It has been proposed that cholinergic amacrine cells provide laminar cues that remodel ganglion cell dendrites, because their processes stratify before those of the ganglion cells. To address this possibility, it is necessary to know whether cholinergic cells contact all or only some classes of ganglion cells during development. We, therefore, used two-photon microscopy to simultaneously reconstruct the dendritic arbors of different classes of ganglion cells and terminal processes of cholinergic cells in neonatal mouse retina. We determined that, after birth, cholinergic cells contacted only a subset of ganglion cells. Large bistratified cells (LBCs), resembling direction selective ganglion cells in other species, had dendrites that fasciculated with the cholinergic plexuses. The LBCs received numerous presynaptic cholinergic contacts shortly after birth. In contrast, large monostratified cells (LMCs), ramifying outside the cholinergic plexuses at maturity, received few, if any, cholinergic contacts even at early stages when their dendrites overlapped with the cholinergic processes. These observations suggest that cholinergic cells provide laminar cues for only subsets of ganglion cells. They also indicate that the synaptic organization between amacrine and ganglion cells may be specified early in development.
哺乳动物视网膜的神经节细胞在其树突局限于内网状层内功能不同的板层之前会经历结构重塑。有人提出，胆碱能无长突细胞提供了重塑神经节细胞树突的板层线索，因为它们的突起比神经节细胞的突起更早分层。为了探究这种可能性，有必要了解胆碱能细胞在发育过程中是与所有神经节细胞类群接触，还是仅与某些类群接触。因此，我们使用双光子显微镜同时重建了新生小鼠视网膜中不同类群神经节细胞的树突分支和胆碱能细胞的终末突起。我们确定，出生后，胆碱能细胞仅与一部分神经节细胞接触。大型双分层细胞（LBCs）类似于其他物种中的方向选择性神经节细胞，其树突与胆碱能丛形成束状。出生后不久，LBCs就接受了大量突触前胆碱能接触。相比之下，大型单分层细胞（LMCs）在成熟时在胆碱能丛之外分支，即使在其树突与胆碱能突起重叠的早期阶段，也很少接受胆碱能接触（如果有的话）。这些观察结果表明，胆碱能细胞仅为部分神经节细胞亚群提供板层线索。它们还表明，无长突细胞和神经节细胞之间的突触组织可能在发育早期就已确定。
