Department of Nuclear Medicine, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
Department of Anatomy and Cell Biology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
J Chem Neuroanat. 2023 Jul;130:102259. doi: 10.1016/j.jchemneu.2023.102259. Epub 2023 Mar 21.
The distribution of the synaptic vesicle protein synaptoporin was investigated by immunofluorescence in the central auditory system of the mouse brainstem. Synaptoporin immunostaining displayed region-specific differences. High and moderate accumulations of were seen in the superficial layer of the dorsal cochlear nucleus, dorsal and external regions of the inferior colliculus, the medial and dorsal divisions of the medial geniculate body and in periolivary regions of the superior olivary complex (SOC). Low or absent labeling was observed in the more central parts of these structures such as the principal nuclei of the SOC. It was conspicuous that dense synaptoporin immunoreactivity was detected predominantly in areas, which are known to be synaptic fields of multimodal, extra-auditory inputs. Target neurons of synaptoporin-positive synapses in the SOC were then identified by double-labelling immunofluorescence microscopy. We thereby detected synaptoporin puncta perisomatically at nitrergic, glutamatergic and serotonergic neurons but none next to neurons immunoreactive for choline-acetyltransferase and calcitonin-gene related peptide. These results leave open whether functionally distinct neuronal groups are accessed in the SOC by synaptoporin-containing neurons. The last part of our study sought to find out whether synaptoporin-positive neurons originate in the medial paralemniscal nucleus (MPL), which is characterized by expression of the peptide parathyroid hormone 2 (PTH2). Anterograde neuronal tracing upon injection into the MPL in combination with synaptoporin- and PTH2-immunodetection showed that (1) the MPL projects to the periolivary SOC using PTH2 as transmitter, (2) synaptoporin-positive neurons do not originate in the MPL, and (3) the close juxtaposition of synaptoporin-staining with either the anterograde tracer or PTH2 reflect concerted action of the different inputs to the SOC.
通过免疫荧光技术研究了突触小泡蛋白 synaptoporin 在小鼠脑干中枢听觉系统中的分布。Synaptoporin 免疫染色显示出区域特异性差异。在耳蜗背核浅层、下丘背侧和外区、内侧膝状体的内侧和背部分区以及上橄榄复合体的periolivery 区观察到高和中度积累。在这些结构的更中心部分，如 SOC 的主要核，观察到低或不存在标记。值得注意的是，密集的 synaptoporin 免疫反应主要在已知是多模态、听觉外输入的突触场的区域中被检测到。然后通过双标免疫荧光显微镜鉴定 SOC 中 synaptoporin 阳性突触的靶神经元。我们因此在 nitrergic、glutamatergic 和 serotonergic 神经元周围检测到 synaptoporin 点状perisomatically，但在胆碱乙酰转移酶和降钙素基因相关肽免疫反应性神经元旁边没有检测到。这些结果表明，在 SOC 中，是否通过含有 synaptoporin 的神经元访问功能不同的神经元群尚不清楚。我们研究的最后一部分旨在确定 synaptoporin 阳性神经元是否起源于内侧旁正中核 (MPL)，该核的特征是表达肽甲状旁腺激素 2 (PTH2)。将 PTH2 用作递质，将顺行神经元追踪物注入 MPL 后，与 synaptoporin 和 PTH2 免疫检测相结合，结果表明：(1)MPL 通过 PTH2 投射到 periolivery SOC；(2)synaptoporin 阳性神经元不是起源于 MPL；(3)synaptoporin 染色与顺行示踪剂或 PTH2 的紧密并置反映了不同输入到 SOC 的协同作用。
