Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
Elife. 2018 Apr 5;7:e34395. doi: 10.7554/eLife.34395.
Rhythmic theta frequency (~5-12 Hz) oscillations coordinate neuronal synchrony and higher frequency oscillations across the cortex. Spatial navigation and context-dependent episodic memories are represented in several interconnected regions including the hippocampal and entorhinal cortices, but the cellular mechanisms for their dynamic coupling remain to be defined. Using monosynaptically-restricted retrograde viral tracing in mice, we identified a subcortical GABAergic input from the medial septum that terminated in the entorhinal cortex, with collaterals innervating the dorsal presubiculum. Extracellularly recording and labeling GABAergic entorhinal-projecting neurons in awake behaving mice show that these subcortical neurons, named orchid cells, fire in long rhythmic bursts during immobility and locomotion. Orchid cells discharge near the peak of hippocampal and entorhinal theta oscillations, couple to entorhinal gamma oscillations, and target subpopulations of extra-hippocampal GABAergic interneurons. Thus, orchid cells are a specialized source of rhythmic subcortical GABAergic modulation of 'upstream' and 'downstream' cortico-cortical circuits involved in mnemonic functions.
节律性θ频率（~5-12 Hz）振荡协调神经元同步和更高频率的皮层振荡。空间导航和情景依赖的情景记忆在包括海马和内嗅皮层在内的几个相互连接的区域中被表示，但它们动态耦合的细胞机制仍有待确定。使用小鼠中单突触限制的逆行病毒追踪，我们鉴定出来自中隔的 GABA 能输入，其终止于内嗅皮层，侧支支配背侧前下托。在清醒行为小鼠中进行细胞外记录和标记 GABA 能内嗅投射神经元显示，这些称为兰花细胞的皮质下神经元在不动和运动期间长节律性爆发。兰花细胞在海马和内嗅θ振荡的峰值附近放电，与内嗅γ振荡耦合，并靶向海马外 GABA 能中间神经元的亚群。因此，兰花细胞是参与记忆功能的“上游”和“下游”皮质皮质回路的节律性皮质下 GABA 能调制的专门来源。
