Wouterlood F G, Härtig W, Brückner G, Witter M P
Department of Anatomy, Vrije Universiteit, Graduate School Neurosciences Amsterdam, The Netherlands.
J Neurocytol. 1995 Feb;24(2):135-53. doi: 10.1007/BF01181556.
We studied the distribution, morphology, ultrastructure and connectivity of parvalbumin-immunoreactive neurons in the entorhinal cortex of the rat. Immunoreactive cell bodies were found in all layers of the entorhinal cortex except layer I. The highest numbers were observed in layers II and III of the dorsal division of the lateral entorhinal area whereas the lowest numbers occurred in the ventral division of the lateral entorhinal area. Most such neurons displayed multipolar configurations with smooth dendrites. We distinguished a type with long dendrites and a type with short dendrites. We also observed pyramidal immunoreactive neurons. A dense plexus of immunoreactive dendrites and axons was prominent in layers II and III of the dorsal division of the lateral entorhinal area and the medial entorhinal area. None of the parvalbumin-immunoreactive cells became retrogradely labelled after injection of horseradish peroxidase into the hippocampal formation. By electron microscopy, immunoreactivity was observed in cell bodies, dendrites, myelinated and unmyelinated axons and axon terminals. Immunoreactive dendrites and axons occurred in all cortical layers. We noted many myelinated immunoreactive axons. Immunoreactive axon terminals were medium sized, contained pleomorphic synaptic vesicles, and established symmetrical synapses. Both horseradish peroxidase labelled and unlabelled immunonegative cell bodies often received synapses from immunopositive axon terminals arranged in baskets. Synapses between immunoreactive axon terminals and unlabelled dendritic shafts and spines were abundant. Synapses with initial axon segments occurred less frequently. In addition, synaptic contacts were present between immunopositive axon terminals and cell bodies and dendrites. Thus, the several types of parvalbumin-containing neuron in the entorhinal cortex are interneurons, connected to one another and to immunonegative neurons through a network of synaptic contacts. Immunonegative cells projecting to the hippocampal formation receive axo-somatic basket synapses from immunopositive terminals. This connectivity may form the morphological substrate underlying the reported strong inhibition of cells in layers II and III of the entorhinal cortex projecting to the hippocampal formation.
我们研究了大鼠内嗅皮质中小清蛋白免疫反应性神经元的分布、形态、超微结构及连接性。在内嗅皮质除I层外的所有层中均发现了免疫反应性细胞体。在内侧内嗅区背侧部的II层和III层中观察到的数量最多，而在内侧内嗅区腹侧部的数量最少。大多数此类神经元呈现多极形态，树突光滑。我们区分出一种长树突类型和一种短树突类型。我们还观察到了呈免疫反应性的锥体神经元。在外侧内嗅区背侧部和内侧内嗅区的II层和III层中，免疫反应性树突和轴突的密集丛很突出。将辣根过氧化物酶注入海马结构后，没有小清蛋白免疫反应性细胞被逆行标记。通过电子显微镜观察，在细胞体、树突、有髓和无髓轴突以及轴突终末中均观察到了免疫反应性。免疫反应性树突和轴突出现在所有皮质层中。我们注意到许多有髓的免疫反应性轴突。免疫反应性轴突终末中等大小，含有多形性突触小泡，并形成对称突触。辣根过氧化物酶标记的和未标记的免疫阴性细胞体常常接受来自呈篮状排列的免疫阳性轴突终末的突触。免疫反应性轴突终末与未标记的树突干和树突棘之间的突触很丰富。与轴突起始段的突触出现频率较低。此外，免疫阳性轴突终末与细胞体和树突之间存在突触联系。因此，内嗅皮质中几种含小清蛋白的神经元是中间神经元，它们通过突触联系网络相互连接并与免疫阴性神经元相连。投射至海马结构的免疫阴性细胞接受来自免疫阳性终末的轴-体篮状突触。这种连接性可能构成了据报道对内嗅皮质II层和III层中投射至海马结构的细胞有强烈抑制作用的形态学基础。
