Miettinen R, Freund T F
Department of Functional Neuroanatomy, Hungarian Academy of Sciences, Budapest.
Brain Res. 1992 Oct 30;594(2):263-72. doi: 10.1016/0006-8993(92)91133-y.
The convergence and segregation of medial septal and median raphe afferents in the innervation of different subpopulations of GABAergic interneurons was investigated in the rat hippocampal formation. Following local injections of 5,7-dihydroxytryptamine into the median raphe nucleus destroying all serotonergic neurons, iontophoretic injections of Phaseolus vulgaris leucoagglutinin (PHAL) into the medial septum resulted in anterograde labelling of axons in the hippocampus. The labelled varicose fibres made multiple contacts with calbindin D28K-, parvalbumin-, and cholecystokinin-immunoreactive interneurons. These results disproved the possibility that PHAL-labelled afferents innervating hippocampal interneurons following septal PHAL injections would have been raphe axons passing through the injection site. In the second set of experiments a double anterograde tracing technique (PHAL from the septum and biotinylated-PHAL from the median raphe) and a triple or double immunostaining procedure was used to determine the types of interneurons (calbindin D28K-, parvalbumin-, or cholecystokinin-immunoreactive) innervated by one, or the other, or both pathways. The results showed that parvalbumin-containing neurons were innervated by septal afferents but avoided by raphe axons, whereas calbindin D28K-containing cells, and to a smaller extent cholecystokinin-containing cells served as targets for both pathways. In some cases the same individual calbindin D28K- or cholecystokinin-containing neurons received multiple contacts from afferents of both septal and raphe origin. Thus, our results indicate that different subcortical nuclei modulate largely different inhibitory circuits in the hippocampal formation. However, considering the occasional convergence of the two subcortical nuclei not only onto the same type, but even onto the same individual calbindin D28K-containing interneurons, we propose that a particular inhibitory function, most probably feed-forward inhibition in the distal dendritic region, is under the control of both pathways.
在大鼠海马结构中，研究了内侧隔核和中缝正中核传入纤维在支配不同亚群GABA能中间神经元时的汇聚和分离情况。在向中缝正中核局部注射5,7 - 二羟基色胺破坏所有血清素能神经元后，将菜豆白细胞凝集素（PHAL）离子导入内侧隔核，导致海马中轴突的顺行标记。标记的曲张纤维与钙结合蛋白D28K、小白蛋白和胆囊收缩素免疫反应性中间神经元有多处接触。这些结果排除了以下可能性：在隔核注射PHAL后，支配海马中间神经元的PHAL标记传入纤维是穿过注射部位的中缝轴突。在第二组实验中，采用双重顺行追踪技术（从隔核注射PHAL，从中缝正中核注射生物素化PHAL）和三重或双重免疫染色程序，以确定由一条或另一条或两条通路支配的中间神经元类型（钙结合蛋白D28K、小白蛋白或胆囊收缩素免疫反应性）。结果表明，含小白蛋白的神经元由隔核传入纤维支配，但中缝轴突不与之接触，而含钙结合蛋白D28K的细胞以及较小程度上含胆囊收缩素的细胞是两条通路的靶标。在某些情况下，同一个含钙结合蛋白D28K或含胆囊收缩素的神经元会同时接受来自隔核和中缝起源的传入纤维的多处接触。因此，我们的结果表明，不同的皮层下核团在很大程度上调节海马结构中不同的抑制性回路。然而，考虑到这两个皮层下核团偶尔不仅会汇聚到同一类型，甚至会汇聚到同一个含钙结合蛋白D28K的中间神经元上，我们提出，一种特定的抑制功能，很可能是远端树突区域的前馈抑制，受两条通路的控制。
