Berrebi A S, Mugnaini E
Laboratory of Neuromorphology, University of Connecticut, Storrs 06269-4154.
Anat Embryol (Berl). 1991;183(5):427-54. doi: 10.1007/BF00186433.
This investigation attempted to determine the mode of distribution and synaptic targets of the cartwheel cell axon in the guinea pig dorsal cochlear nucleus (DCoN). Antiserum against PEP-19, a putative calcium-binding neuropeptide, was employed at the light and electron microscopic levels. We show that in the hind-brain of the guinea pig, cerebellar Purkinje cells and DCoN cartwheel cells are the most densely immunoreactive neurons. The PEP-19 immunoreaction product is localized to all neuronal compartments of these cells. Primary targets of cartwheel cell axons are the DCoN pyramidal cells, the large efferent neurons of layer 2. These neurons receive numerous immunoreactive synaptic boutons on their cell bodies and apical and basal dendritic arbors. A PEP-19-immunoreactive axonal plexus, largely formed by cartwheel cell axons, highlights layer 3, co-extensively with the basal arbors of pyramidal cells. This plexus is oriented predominantly in the transstrial plane of the DCoN, in parallel with the sheet-like basal dendritic arbor of pyramidal neurons and with the isofrequency bands of primary cochlear nerve fibers. PEP-19-positive boutons contain pleomorphic synaptic vesicles and form symmetric synaptic junctions, indicative of inhibitory innervation. In addition, immunoreactive boutons, similar to those synapsing on pyramidal neurons, were observed on the cell bodies and main dendritic trunks of cartwheel neurons, indicating a system of recurrent collaterals. Furthermore, a small number of PEP-19-positive axons of unknown origin reach the caudal rim of the posteroventral cochlear nucleus. Within the territory of distribution of the cartwheel cell axon are the dendrites of at least two other types of DCoN neuron, the vertical cells of Lorente de Nó and the giant cells. These neurons may represent additional targets of the cartwheel cell axon, but this remains to be ascertained with specific methods. Our data demonstrate that the cartwheel neurons modulate the activity of pyramidal neurons and, therefore, play a key role in shaping the output of the DCoN superficial layers.
本研究试图确定豚鼠背侧耳蜗核（DCoN）中车轮状细胞轴突的分布模式和突触靶点。在光镜和电镜水平上使用了针对假定的钙结合神经肽PEP - 19的抗血清。我们发现，在豚鼠的后脑，小脑浦肯野细胞和DCoN车轮状细胞是免疫反应性最强的神经元。PEP - 19免疫反应产物定位于这些细胞的所有神经亚区。车轮状细胞轴突的主要靶点是DCoN锥体细胞，即第2层的大型传出神经元。这些神经元在其胞体以及顶端和基底树突分支上接受大量免疫反应性突触小体。一个主要由车轮状细胞轴突形成的PEP - 19免疫反应性轴突丛突出了第3层，与锥体细胞的基底分支共同延伸。该丛主要沿DCoN的跨层平面定向，与锥体细胞片状的基底树突分支以及初级耳蜗神经纤维的等频带平行。PEP - 19阳性的突触小体含有多形性突触小泡并形成对称性突触连接，表明是抑制性神经支配。此外，在车轮状神经元的胞体和主要树突干上观察到与那些与锥体细胞形成突触的类似的免疫反应性突触小体，表明存在一个回返侧支系统。此外，少量来源不明的PEP - 19阳性轴突到达后腹侧耳蜗核的尾缘。在车轮状细胞轴突的分布区域内有至少两种其他类型的DCoN神经元的树突，即洛伦特·德·诺垂直细胞和巨细胞。这些神经元可能是车轮状细胞轴突的额外靶点，但这仍有待用特定方法确定。我们的数据表明，车轮状神经元调节锥体细胞的活动，因此在塑造DCoN表层的输出中起关键作用。
