PDF(Pubmed)
Abstract：
BACKGROUND: Granule cells in the hippocampus project axons to hippocampal CA3 pyramidal cells where they form large mossy fiber terminals. We have reported that these terminals contain the gap junction protein connexin36 (Cx36) specifically in the stratum lucidum of rat ventral hippocampus, thus creating morphologically mixed synapses that have the potential for dual chemical/electrical transmission.
METHODS: Here, we used various approaches to characterize molecular and electrophysiological relationships between the Cx36-containing gap junctions at mossy fiber terminals and their postsynaptic elements and to examine molecular relationships at mixed synapses in the brainstem.
RESULTS: In rat and human ventral hippocampus, many of these terminals, identified by their selective expression of vesicular zinc transporter-3 (ZnT3), displayed multiple, immunofluorescent Cx36-puncta representing gap junctions, which were absent at mossy fiber terminals in the dorsal hippocampus. In rat, these were found in close proximity to the protein constituents of adherens junctions (i.e., N-cadherin and nectin-1) that are structural hallmarks of mossy fiber terminals, linking these terminals to the dendritic shafts of CA3 pyramidal cells, thus indicating the loci of gap junctions at these contacts. Cx36-puncta were also associated with adherens junctions at mixed synapses in the brainstem, supporting emerging views of the structural organization of the adherens junction-neuronal gap junction complex. Electrophysiologically induced long-term potentiation (LTP) of field responses evoked by mossy fiber stimulation was greater in the ventral than dorsal hippocampus.
CONCLUSIONS: The electrical component of transmission at mossy fiber terminals may contribute to enhanced LTP responses in the ventral hippocampus.
METHODS: Here, we used various approaches to characterize molecular and electrophysiological relationships between the Cx36-containing gap junctions at mossy fiber terminals and their postsynaptic elements and to examine molecular relationships at mixed synapses in the brainstem.
RESULTS: In rat and human ventral hippocampus, many of these terminals, identified by their selective expression of vesicular zinc transporter-3 (ZnT3), displayed multiple, immunofluorescent Cx36-puncta representing gap junctions, which were absent at mossy fiber terminals in the dorsal hippocampus. In rat, these were found in close proximity to the protein constituents of adherens junctions (i.e., N-cadherin and nectin-1) that are structural hallmarks of mossy fiber terminals, linking these terminals to the dendritic shafts of CA3 pyramidal cells, thus indicating the loci of gap junctions at these contacts. Cx36-puncta were also associated with adherens junctions at mixed synapses in the brainstem, supporting emerging views of the structural organization of the adherens junction-neuronal gap junction complex. Electrophysiologically induced long-term potentiation (LTP) of field responses evoked by mossy fiber stimulation was greater in the ventral than dorsal hippocampus.
CONCLUSIONS: The electrical component of transmission at mossy fiber terminals may contribute to enhanced LTP responses in the ventral hippocampus.
摘要：
背景：海马中的颗粒细胞将轴突投射到海马CA3锥体细胞，在那里它们形成大的苔藓纤维末端。我们已经报道，这些末端含有间隙连接蛋白connexin36（Cx36），特别是在大鼠腹侧海马的透明层中，从而产生具有双重化学/电传输潜力的形态学混合突触。
方法：这里，我们使用各种方法来表征苔藓纤维末端含Cx36的间隙连接与其突触后元件之间的分子和电生理关系,并检查脑干混合突触的分子关系.
结果：在大鼠和人类腹侧海马中，其中许多终端，通过它们选择性表达囊泡锌转运蛋白3（ZnT3）鉴定，显示多个，免疫荧光Cx36-puncta代表间隙连接，在背侧海马的苔藓纤维末端不存在。在老鼠身上，这些被发现与粘附连接的蛋白质成分非常接近(即，N-cadherin和nectin-1）是苔藓纤维末端的结构标志，将这些末端连接到CA3锥体细胞的树突轴，从而表明这些接触处的间隙连接位点。Cx36-puncta也与脑干混合突触处的粘附连接有关，支持粘附连接-神经元间隙连接复合体结构组织的新观点。由苔藓纤维刺激引起的电生理诱导的场反应的长期增强（LTP）在腹侧比背侧海马更大。
结论：苔藓纤维末端传输的电成分可能有助于增强腹侧海马的LTP反应。
方法：这里，我们使用各种方法来表征苔藓纤维末端含Cx36的间隙连接与其突触后元件之间的分子和电生理关系,并检查脑干混合突触的分子关系.
结果：在大鼠和人类腹侧海马中，其中许多终端，通过它们选择性表达囊泡锌转运蛋白3（ZnT3）鉴定，显示多个，免疫荧光Cx36-puncta代表间隙连接，在背侧海马的苔藓纤维末端不存在。在老鼠身上，这些被发现与粘附连接的蛋白质成分非常接近(即，N-cadherin和nectin-1）是苔藓纤维末端的结构标志，将这些末端连接到CA3锥体细胞的树突轴，从而表明这些接触处的间隙连接位点。Cx36-puncta也与脑干混合突触处的粘附连接有关，支持粘附连接-神经元间隙连接复合体结构组织的新观点。由苔藓纤维刺激引起的电生理诱导的场反应的长期增强（LTP）在腹侧比背侧海马更大。
结论：苔藓纤维末端传输的电成分可能有助于增强腹侧海马的LTP反应。
