Kishi K, Mori K, Ojima H
J Comp Neurol. 1984 Jun 1;225(4):511-26. doi: 10.1002/cne.902250404.
To determine the projection fields of intrabulbar axon collaterals, mitral, displaced mitral, and middle tufted cells in the rabbit olfactory bulb were stained by intracellular injection of HRP. The axon collaterals of mitral cells and displaced mitral cells were distributed exclusively within the granule cell layer (GrL). Those of middle tufted cells were distributed mostly in the GrL and on rare occasions in the mitral cell layer. None of these collaterals entered the external plexiform layer. Axon collaterals of mitral cells, emitted at the depths of the GrL, were distributed widely from the deep portion to the most superficial portion of the GrL. Collaterals of displaced mitral cells were also emitted in the deep part, but they tended to be distributed more superficially in the GrL than mitral cells. Collaterals of middle tufted cells were released and distributed superficially in the GrL. The axon collaterals of these principal cells typically extended for a longer distance than the secondary dendrites, and they sometimes formed bushlike terminal arborizations. The results indicate that the projection fields of the axon collaterals of principal cells are spatially separated from the dendritic projection fields. This suggests that the output of these principal cells through the collaterals has a functionally different role from the output through the dendrites. The observation that the three types of principal cells differ in the distribution pattern of their axon collaterals in the GrL suggests that there is a functional separation of the sublayers in the GrL.
为了确定球内轴突侧支的投射区域，通过细胞内注射辣根过氧化物酶（HRP）对兔嗅球中的二尖瓣细胞、移位二尖瓣细胞和中簇状细胞进行染色。二尖瓣细胞和移位二尖瓣细胞的轴突侧支仅分布在颗粒细胞层（GrL）内。中簇状细胞的轴突侧支大多分布在颗粒细胞层，偶尔也分布在二尖瓣细胞层。这些侧支均未进入外丛状层。二尖瓣细胞的轴突侧支在颗粒细胞层深处发出，从颗粒细胞层的深部到最表层广泛分布。移位二尖瓣细胞的侧支也在深部发出，但它们在颗粒细胞层中的分布比二尖瓣细胞更靠近表层。中簇状细胞的侧支在颗粒细胞层表面释放和分布。这些主要细胞的轴突侧支通常比二级树突延伸的距离更长，并且它们有时会形成灌木丛状的终末分支。结果表明，主要细胞的轴突侧支投射区域在空间上与树突投射区域分开。这表明这些主要细胞通过侧支的输出与通过树突的输出在功能上具有不同的作用。三种主要细胞在颗粒细胞层中轴突侧支分布模式不同的观察结果表明，颗粒细胞层的亚层存在功能分离。
