Wong-Riley M T, Norton T T
Department of Anatomy and Cellular Biology, Medical College of Wisconsin, Milwaukee 53226.
J Comp Neurol. 1988 Jun 22;272(4):562-78. doi: 10.1002/cne.902720409.
The tree shrew Tupaia belangeri has three functional pathways (ON-center, OFF-center, and W-like cells) that arise in the retina and proceed through separate LGN laminae to separate cortical targets. To determine whether these pathways have consistent differences in activity, cytochrome oxidase (C.O.) patterns were examined in the retina, LGN, and striate cortex. In six normal tree shrews the outer and inner plexiform layers of the retina were highly reactive for C.O. A pale, vascularized cleft zone separated the a (OFF) and b (ON) inner plexiform sublaminae, which seemed about equally reactive for C.O. In the LGN, laminae 1 and 2 (ON-center cells) and laminae 4 and 5 (mostly OFF-center cells) were highly reactive for C.O. LGN lamina 3 and 6 are part of an W-like afferent pathway. Lamina 3 was distinctly paler than laminae 1, 2, 4, and 5 while lamina 6 was intermediate. In the striate cortex, layer IV was the most reactive layer. Sublayer IVb (predominantly an OFF region) was consistently more reactive than sublayer IVa (predominantly ON). The middle portion, layer IVm, was paler than either IVa or IVb. This paler region includes, but extends above and below, the cell-sparse "cleft" region. Thus, considering all three levels of the retinogeniculostriate pathway, the ON and OFF systems were equally active until they reached the striate cortex, where the OFF system appeared to be more active than the ON. The W-cell laminae in the LGN exhibited the lowest level of activity. The contribution of ganglion cell activity to these patterns was assessed by intravitreal administration of tetrodotoxin (TTX) blockade either monocularly (three animals) or binocularly (two animals). In the TTX-treated retinae, the inner plexiform a and b sublaminae were paler for C.O., although visible, and were still separated by the pale cleft. The ganglion cell layer was very pale in comparison to the normal. In the LGN, monocular TTX blockade reduced the C.O. reactivity in the ON and OFF laminae that received input from the treated eye but had little effect on the W-like cell laminae. The ipsilaterally innervated ON and OFF laminae were more affected than were the contralaterally innervated laminae. Binocular TTX treatment resulted in a decrease of C.O. activity in the binocular segment of the ON and OFF LGN laminae. In the striate cortex, the most marked changes following TTX treatment occurred in layer IV.(ABSTRACT TRUNCATED AT 400 WORDS)
树鼩（Tupaia belangeri）具有三种功能性通路（ON中心、OFF中心和W样细胞），这些通路起源于视网膜，并通过不同的外侧膝状体层到达不同的皮质靶点。为了确定这些通路在活性上是否存在一致的差异，我们检测了视网膜、外侧膝状体和纹状皮质中的细胞色素氧化酶（C.O.）模式。在六只正常树鼩中，视网膜的外网状层和内网状层对C.O.反应强烈。一个浅色的、血管化的裂隙区域将内网状层的a（OFF）和b（ON）亚层分开，这两个亚层对C.O.的反应似乎大致相同。在外侧膝状体中，第1和第2层（ON中心细胞）以及第4和第5层（主要是OFF中心细胞）对C.O.反应强烈。外侧膝状体第3和第6层是W样传入通路的一部分。第3层明显比第1、2、4和5层更浅，而第6层则介于两者之间。在纹状皮质中，第IV层是反应最强烈的层。IVb亚层（主要是OFF区域）始终比IVa亚层（主要是ON）反应更强。中间部分，即IVm层，比IVa或IVb层更浅。这个较浅的区域包括但不限于细胞稀疏的“裂隙”区域，并且向上和向下延伸。因此，考虑到视网膜 - 外侧膝状体 - 纹状皮质通路的所有三个层次，ON和OFF系统在到达纹状皮质之前活性相当，而在纹状皮质中，OFF系统似乎比ON系统更活跃。外侧膝状体中的W细胞层活性最低。通过玻璃体内注射河豚毒素（TTX）进行单眼（三只动物）或双眼（两只动物）阻断来评估神经节细胞活性对这些模式的贡献。在接受TTX处理的视网膜中，内网状层的a和b亚层对C.O.来说更浅，尽管仍可见，并且仍被浅色裂隙分开。与正常情况相比，神经节细胞层非常浅。在外侧膝状体中，单眼TTX阻断降低了接受来自处理眼输入的ON和OFF层中的C.O.反应性，但对W样细胞层影响很小。同侧支配的ON和OFF层比 contralaterally 支配的层受影响更大。双眼TTX处理导致ON和OFF外侧膝状体层的双眼段中C.O.活性降低。在纹状皮质中，TTX处理后最明显的变化发生在第IV层。（摘要截断于400字） （注：原文中“contralaterally”疑为拼写错误，推测可能是“contralaterally innervated”，意为“对侧支配的”，这里暂按推测翻译，若有更准确信息可进一步完善。）
