Jacomy H, Bosler O
Laboratoire de Neuroendocrinologie Expérimentale, INSERM U297, Institut Fédératif Jean Roche, Faculté de Médecine, Marseille, France.
Cell Tissue Res. 1995 Apr;280(1):87-96. doi: 10.1007/BF00304514.
Catecholaminergic fibers in the suprachiasmatic nucleus of adult rats were investigated by use of light- and electron-microscopic immunocytochemistry. The suprachiasmatic nucleus receives a modest density of tyrosine hydroxylase-containing axons, homogeneously distributed in the nucleus and forming varicosities throughout its entire rostro-caudal extension. Immunolabeling with antibodies against dopamine showed that this catecholamine input comprises a dopaminergic component. Many tyrosine hydroxylase-positive cells were localized at the immediate periphery of the suprachiasmatic nucleus. With electron-microscopic examination, dendrites of these neurons were found within the limits of the nucleus as well as at a border zone between the suprachiasmatic nucleus proper and the optic tract where they received unlabeled synapses, providing a morphological support for a possible role of dopaminergic neurons in the integration and/or transfer of light-related signals. More than 91% of catecholaminergic axonal varicosities were found to establish morphologically defined synapses with dendrites. To investigate whether these synapses might be shared with neurons of one or both of the two main peptidergic populations of the nucleus, namely vasoactive intestinal peptide- and vasopressin-containing neurons, we carried out double-labelling experiments combining immunoperoxidase and immunogold-silver labeling. Results showed only a few cases of direct association of the catecholaminergic terminals with these peptidergic categories. In both types of dually stained sections, catecholaminergic synapses were preferentially made with unlabeled dendrites. The homogeneous distribution of tyrosine hydroxylase-immunoreactive fibers in the suprachiasmatic nucleus could therefore reflect a lack of significant catecholaminergic innervation of both vasoactive intestinal peptide- and vasopressin-synthesizing neurons.
利用光镜和电镜免疫细胞化学技术，对成年大鼠视交叉上核中的儿茶酚胺能纤维进行了研究。视交叉上核接受中等密度的含酪氨酸羟化酶的轴突，这些轴突均匀分布于核内，并在其整个 rostro-caudal 延伸范围内形成膨体。用抗多巴胺抗体进行免疫标记显示，这种儿茶酚胺输入包含一个多巴胺能成分。许多酪氨酸羟化酶阳性细胞位于视交叉上核的紧邻周边。通过电镜检查发现，这些神经元的树突位于核内以及视交叉上核与视束之间的边界区域，在那里它们接受未标记的突触，这为多巴胺能神经元在光相关信号整合和/或传递中的可能作用提供了形态学支持。超过91%的儿茶酚胺能轴突膨体被发现与树突形成形态学上明确的突触。为了研究这些突触是否可能与该核的两个主要肽能神经元群体之一或两者共享，即含血管活性肠肽和含加压素的神经元，我们进行了结合免疫过氧化物酶和免疫金银标记的双重标记实验。结果显示，儿茶酚胺能终末与这些肽能类别直接关联的情况很少。在两种双重染色的切片中，儿茶酚胺能突触优先与未标记的树突形成。因此，视交叉上核中酪氨酸羟化酶免疫反应性纤维的均匀分布可能反映出血管活性肠肽和加压素合成神经元缺乏显著的儿茶酚胺能神经支配。
