Schoenfeld T A, Marchand J E, Macrides F
J Comp Neurol. 1985 May 22;235(4):503-18. doi: 10.1002/cne.902350408.
The organization of intrinsic axonal projections of principal neurons in the main olfactory bulb (MOB) was studied in hamsters by using wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and fluorescent dyes. Punctate injections of either WGA-HRP or fast blue (FB) that are restricted to small sectors on one side of the MOB produce comparably restricted fields of retrograde labeling on the opposite side. Label is found predominantly in superficially situated (middle and external) tufted cells that lie near and at the border between the external plexiform and glomerular layers. Few of the deeper middle tufted, internal tufted, or mitral cells and no external tufted cells that lie in the superficial two-thirds of the glomerular layer are labeled in regions remote to the injection site. Anterograde transport of WGA-HRP from the injection site labels axons that travel dorsally and ventrally in restricted bands through the internal plexiform layer and then terminate within this layer in the punctate sector on the opposite side that contains retrogradely labeled neurons. Such reciprocal projections between opposing regions of the medial and lateral sides of the MOB are found at all rostrocaudal and dorsoventral levels. When punctate injections of FB into the MOB are paired with restricted injections of a second fluorescent tracer (nuclear yellow or diamidino yellow dihydrochloride) into the appropriate sector of pars externa (pE) of the anterior olfactory nucleus, the punctate region of remote retrogradely labeled principal neurons is embedded within a topographically restricted longitudinal wedge of retrogradely labeled mitral and tufted cells that project extrinsically to or through pE. However, extremely few of these neurons are double-retrogradely labeled. The results reveal the existence of an intrabulbar associational system in which principal neurons engage in point-to-point, reciprocal projections between opposing regions of the medial and lateral MOB. Moreover, the results indicate that this associational system largely arises from superficially situated tufted cells distinct from those that support bulbofugal projections into the topographically organized interbulbar commissural system via pE.
通过使用小麦胚凝集素-辣根过氧化物酶（WGA-HRP）和荧光染料，对仓鼠主嗅球（MOB）中主要神经元的固有轴突投射组织进行了研究。将WGA-HRP或快蓝（FB）点状注射到MOB一侧的小区域内，在另一侧会产生相应局限的逆行标记区域。标记主要出现在位于外丛状层和肾小球层之间及边界附近的浅表层（中层和外层）簇状细胞中。在远离注射部位的区域，很少有较深的中层簇状细胞、内层簇状细胞或二尖瓣细胞被标记，而位于肾小球层上三分之二浅表层的外层簇状细胞则没有被标记。从注射部位进行的WGA-HRP顺行运输标记了轴突，这些轴突在内部丛状层中以局限的束状向背侧和腹侧延伸，然后在包含逆行标记神经元的对侧点状区域内终止于该层。在MOB内侧和外侧相对区域之间的这种相互投射在所有前后和背腹水平都能发现。当将FB点状注射到MOB中，并与将第二种荧光示踪剂（核黄或二盐酸双脒基黄）局限注射到前嗅核外侧部（pE）的适当区域配对时，远程逆行标记主要神经元的点状区域被嵌入到逆行标记的二尖瓣和簇状细胞的地形学局限纵向楔内，这些细胞向外投射到pE或通过pE。然而，这些神经元中极少有被双重逆行标记的。结果揭示了存在一个球内联合系统，其中主要神经元在MOB内侧和外侧的相对区域之间进行点对点的相互投射。此外，结果表明这个联合系统主要源自浅表层的簇状细胞，这些细胞与那些通过pE支持向地形学组织的球间连合系统投射的细胞不同。
