AUTORADIOGRAPHIC STUDY OF COMMISSURAL AND IPSILATERAL HIPPOCAMPO-DENTATE PROJECTIONS IN ADULT RAT
AUTORADIOGRAPHIC STUDY OF COMMISSURAL AND IPSILATERAL HIPPOCAMPO-DENTATE PROJECTIONS IN ADULT RAT
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DOI：
10.1002/cne.901810204
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发表时间：
1978-01-01
影响因子：
2.5
通讯作者：
COWAN, WM
中科院分区：
文献类型：
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作者：
FRICKE, R;COWAN, WM
将 3H-脯氨酸少量注射到齿状回的肺门区域（两组传入神经均从该区域产生）后，通过放射自显影研究了关联传入神经和连合传入神经在大鼠齿状回分子层内 1/4 的分布。注射到海马的颞部（即尾部）、中部或间隔（喙部）三分之一后，观察到不同的轴突标记模式。因此，在颞叶注射后，仅在齿状回的尾部 1/3 中发现标记的连合和关联传入神经，并且在两侧观察到的颗粒密度围绕齿状回的短轴或横轴明显不对称。注射到海马体的中间 1/3 会导致整个齿状回头侧 2/3 的连合和关联传入神经被广泛标记，并且根据颗粒密度估计判断，它们的分布在两侧是对称的。间隔注射标记齿状突前 1/2 上方的纤维，并且两侧的标记图案也是不对称的（但与颞部注射后看到的图案相反）。两类传入神经分布的这些独特模式通常可以根据以下假设来解释：连合传入神经和关联传入神经具有共同的细胞化学特异性；它们相互竞争颗粒细胞近端部分上有限数量的可用突触位点；颗粒细胞沿着两个不同的形态发生梯度产生：从齿状回的颞部到间隔极，以及从其背侧（或外部）尖端到腹侧（内部）叶片的尖端；第一个到达的纤维垄断了大部分可用的突触位点，而那些稍后到达目标区域的纤维则主要在最后形成的颗粒细胞树突上形成突触。从这个意义上说，这些发现与 Gottlieb 和 Cowan (1972) 首先提出的时间假设是一致的。为了解释来自海马颞部的传入神经的有限分布，有必要进一步假设同侧和对侧海马齿状投影存在一定程度的地形（或区域到区域）特异性。
The distribution of the associational and commissural afferents to the inner 1/4 of the molecular layer of the dentate gyrus of the rat, was studied autoradiographically following small injections of 3H-proline into the hilar region of the dentate (from which both groups of afferents arise). Different patterns of axonal labeling are observed after injections into the temporal (i.e., caudal), middle, or septal (rostral) thirds of the hippocampus. Thus after temporal injections labeled commissural and associational afferents are found only in the caudal 1/3 of the dentate gyrus, and the grain densities observed on the 2 sides are markedly asymmetrical around the short, or transverse, axis of the dentate. Injections into the middle 1/3 of the hippocampus lead to extensive labeling of the commissural and associational afferents throughout the rostral 2/3 of the dentate gyrus, and their distribution, as judged by grain density estimates, is symmetrical on the 2 sides. Septal injections label fibers over the rostral 1/2 of the dentate, and again the labeling pattern on the 2 sides is asymmetrical (but in the reverse pattern from that seen after temporal injections). These distinctive patterns in the distribution of the 2 classes of afferents can generally be accounted for on the following assumptions: the commissural and associational afferents share a common cytochemical specificity; they compete with each other for the limited number of synaptic sites available upon the proximal portions of the granule cells; the granule cells are generated along 2 distinct morphogenetic gradients: from the temporal to the septal pole of the dentate gyrus, and from the tip of its dorsal (or external) to the tip of its ventral (internal) blade; and the first fibers to arrive monopolize the majority of the available synaptic sites, and those that reach their target field later, synapse predominantly upon the last-formed granule cell dendrites. To this extent these findings are consonant with the temporal hypothesis first formulated by Gottlieb and Cowan (1972). To account for the restricted distribution of afferents from the temporal part of the hippocampus, it is necessary to further postulate that there is some degree of topographic (or region-to-region) specificity in the ipsilateral and contralateral hippocampo-dentate projections.