Sanderson K J, Haight J R, Pettigrew J D
J Comp Neurol. 1984 Mar 20;224(1):85-106. doi: 10.1002/cne.902240108.
The anatomy of the dorsal lateral geniculate nucleus (LGd) is described in five macropodid species, including two rat kangaroos (bettong and potoroo), two wallabies (pademelon and tammar), and the large grey kangaroo. The distribution of retinal terminals in the LGd was examined following intraocular injections of tritiated amino acids. There are considerable differences in both LGd cytoarchitecture and the patterns of retinal terminations among the five species. Cytoarchitecture in the bettong LGd is relatively simple, displaying a minimal regional differentiation. In contrast, the potoroo LGd is quite complex and displays several well-defined cell laminae, each of which is associated with input from a single eye. Both rat kangaroos display the same basic pattern of retinal termination with three bands of terminals from the contralateral eye and four from the ipsilateral eye. The bands are less sharply defined in the bettong, in which terminals from each eye overlap to a greater extent than is seen in the potoroo. The wallabies and kangaroos display a more complex LGd architecture and patterning of retinal terminal bands. Bilateral retinal projections within the same LGd lamina are unusual in these large macropodids. The number of terminal bands reaches ten in the grey kangaroo--four from the contralateral eye and six from the ipsilateral eye. The pademelon LGd is unusual in that it shows intraspecies variation with some animals displaying five ipsilateral terminal bands and others only four. The results are discussed in comparison with the patterns of LGd organisation observed in other mammalian lines, placental and marsupial. We conclude that LGd lamination and the segregation of retinal inputs to the LGd in marsupials are likely to be the result of evolutionary factors which differ from those which have produced ocular segregation and complex lamination in several lines of placental mammals.
本文描述了五种袋鼠科动物背外侧膝状核（LGd）的解剖结构，包括两种鼠袋鼠（长尾袋鼠和长鼻袋鼠）、两种小袋鼠（赤褐袋鼠和帚尾袋貂）以及大灰袋鼠。通过眼内注射氚标记氨基酸后，研究了视网膜终末在LGd中的分布情况。这五个物种的LGd细胞结构和视网膜终末模式存在显著差异。长尾袋鼠LGd的细胞结构相对简单，区域分化不明显。相比之下，长鼻袋鼠的LGd相当复杂，呈现出几个明确的细胞层状结构，每个细胞层都与单眼输入相关。两种鼠袋鼠的视网膜终末基本模式相同，对侧眼有三条终末带，同侧眼有四条终末带。在长尾袋鼠中，这些带的界定不太清晰，每只眼睛的终末比长鼻袋鼠有更大程度的重叠。小袋鼠和大袋鼠的LGd结构以及视网膜终末带模式更为复杂。在这些大型袋鼠科动物中，同一LGd层内的双侧视网膜投射并不常见。大灰袋鼠的终末带数量达到十条——对侧眼四条，同侧眼六条。赤褐袋鼠的LGd不同寻常之处在于，它表现出种内变异，一些动物有五条同侧终末带，而另一些只有四条。本文将这些结果与在其他哺乳动物谱系（有胎盘类和有袋类）中观察到的LGd组织模式进行了比较讨论。我们得出结论，有袋类动物LGd的分层以及视网膜输入到LGd的分离，可能是进化因素的结果，这些因素与导致几条有胎盘类哺乳动物谱系中眼部分离和复杂分层的因素不同。
