Duncan H J, Nickell W T, Shipley M T, Gesteland R C
Department of Anatomy and Cell Biology, University of Cincinnati College of Medicine, Ohio 45267-0521.
J Comp Neurol. 1990 Sep 15;299(3):299-311. doi: 10.1002/cne.902990304.
One hypothesis for the coding of olfactory quality is that regions of the olfactory epithelium are differentially sensitive to particular odor qualities and that this regional sensitivity is conveyed to the olfactory bulb in a topographic manner by the olfactory nerve. A corollary to this hypothesis is that there is a sufficiently orderly connection between the epithelium and the olfactory bulb to convey this topographical coding. Thus we examined topography in the projection from epithelium to bulb in the frog, which has been the subject of numerous electrophysiological studies but has not yet been examined using modern neuroanatomical techniques. The tracer WGA-HRP was applied to the ventral or to the dorsal olfactory epithelium, or both. Anterograde transport of label to the olfactory bulb was seen after as few as 2 days; label was still present in the bulb as long as 21 days postinjection. In cases where WGA-HRP was applied to the entire epithelium, there was dense anterograde labelling of the ipsilateral olfactory bulb. In addition, a small medial portion of the contralateral bulb was labelled. Injections limited to either the ventral or dorsal epithelium produced patterns of anterograde labelling in the glomerular layer of the olfactory bulb, which varied with the size and location of the injection. With very large injections in either the dorsal or ventral epithelium, label appeared to be evenly distributed in the glomerular layer. With smaller injections in the ventral epithelium, there was heavier labelling in the lateral than in the medial portions of the glomerular layer, although light labelling was found in all regions of the glomerular layer. In contrast, injection sites restricted to the dorsal epithelium produced more anterograde labelling in the medial than lateral portions of the glomerular layer. These patterns extended throughout the dorsal-ventral extent of the bulb. Within the limits of the anterograde tracing technique used, we were unable to detect any systematic relationship between the pattern of labelling in the glomerular layer and the medial-lateral or rostral-caudal location of the injection site in either the ventral or dorsal epithelium. We conclude that in the frog, as in other amphibia, there is only a limited degree of topographic order between the epithelium and the olfactory bulb.
一种关于嗅觉质量编码的假说认为，嗅上皮的不同区域对特定的气味质量具有不同的敏感性，并且这种区域敏感性通过嗅神经以拓扑方式传递到嗅球。该假说的一个推论是，上皮和嗅球之间存在足够有序的连接以传递这种拓扑编码。因此，我们研究了青蛙上皮到嗅球投射的拓扑结构，青蛙一直是众多电生理研究的对象，但尚未使用现代神经解剖学技术进行研究。将示踪剂WGA - HRP应用于腹侧或背侧嗅上皮，或两者都应用。注射后仅2天就可见标记物向嗅球的顺行运输；注射后长达21天，标记物仍存在于嗅球中。在将WGA - HRP应用于整个上皮的情况下，同侧嗅球有密集的顺行标记。此外，对侧嗅球的一小部分内侧也有标记。局限于腹侧或背侧上皮的注射在嗅球的肾小球层产生了顺行标记模式，其随注射的大小和位置而变化。在背侧或腹侧上皮进行非常大的注射时，标记物似乎均匀分布在肾小球层。在腹侧上皮进行较小的注射时，肾小球层外侧的标记比内侧更重，尽管在肾小球层的所有区域都发现了轻微标记。相比之下，局限于背侧上皮的注射部位在肾小球层内侧产生的顺行标记比外侧更多。这些模式贯穿嗅球的背腹范围。在所使用的顺行追踪技术的限度内，我们无法检测到肾小球层的标记模式与腹侧或背侧上皮中注射部位的内外侧或前后位置之间存在任何系统关系。我们得出结论，在青蛙中，与其他两栖动物一样，上皮和嗅球之间仅存在有限程度的拓扑顺序。
