The hippocampus is a medial temporal lobe structure in the brain and is widely studied for its role in memory and learning, in particular, spacial memory and emotional responses. It was thought to be a homogenous structure but emerging evidence shows differentiation along the dorsoventral axis and even microdomains for functional and cellular markers. We have examined in two cell‐types of the hippocampal projection neurons, the dentate gyrus (DG) granule cells and CA3 pyramidal neurons, if the GABA‐activated tonic current density varied between the dorsal (septal) and the ventral (temporal) poles of the male mouse hippocampus. Tonic synaptic currents, arising from spontaneous and miniature inhibitory postsynaptic currents (sIPSC, mIPSC), and extrasynaptic tonic currents were evaluated. The results revealed different levels of sIPSC but not mIPSC density between the dorsal and ventral hippocampal neurons for both the DG granule cells and the CA3 pyramidal neurons. The extrasynaptic tonic current density was larger in the DG granule cells as compared to the CA3 pyramidal neurons but did not vary between the dorsal and ventral regions. IPSC bursting was observed in both cell‐types in the ventral hippocampus but was more common in the CA3 pyramidal neurons. Only in the dorsal DG granule cells was the level of the sIPSC and mIPSC density similar. The results indicate that the tonic GABAergic inhibition is particularly strong in the ventral hippocampal DG granule cells and enhanced in the dorsal as compared to the ventral hippocampal CA3 pyramidal neurons.

中文翻译：

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沿小鼠海马背腹轴的齿状回颗粒细胞和 CA3 锥体神经元中滋补 GABA 激活的突触和突触外电流。

海马体是大脑的内侧颞叶结构，因其在记忆和学习，特别是空间记忆和情绪反应中的作用而被广泛研究。它被认为是一种同质结构，但新出现的证据显示沿着背腹轴的分化，甚至是功能和细胞标记的微域。我们已经检查了海马投射神经元的两种细胞类型，齿状回 (DG) 颗粒细胞和 CA3 锥体神经元，如果 GABA 激活的强直电流密度在背侧（隔膜）和腹侧（颞）极之间变化雄性小鼠海马体。对由自发和微型抑制性突触后电流 (sIPSC、mIPSC) 产生的强直突触电流和突触外强直电流进行了评估。结果显示 DG 颗粒细胞和 CA3 锥体神经元的背侧和腹侧海马神经元之间存在不同水平的 sIPSC，但没有 mIPSC 密度。与 CA3 锥体神经元相比，DG 颗粒细胞中的突触外强直电流密度更大，但在背侧和腹侧区域之间没有变化。在腹侧海马的两种细胞类型中都观察到 IPSC 爆发，但在 CA3 锥体神经元中更常见。仅在背侧 DG 颗粒细胞中 sIPSC 和 mIPSC 密度的水平相似。结果表明，与腹侧海马 CA3 锥体神经元相比，强直 GABA 能抑制在腹侧海马 DG 颗粒细胞中特别强，并在背侧增强。