Kavli Institute for Systems Neuroscience and Centre for the Biology of Memory, Norwegian University of Science and Technology, Trondheim, Norway.
Hippocampus. 2012 Jun;22(6):1256-76. doi: 10.1002/hipo.20997. Epub 2011 Dec 7.
The lateral entorhinal cortex (LEC) provides a major cortical input to the hippocampal formation, equaling that of the medial entorhinal cortex (MEC). To understand the functional contributions made by LEC, basic knowledge of individual neurons, in the context of the intrinsic network, is needed. The aim of this study is to compare physiological and morphological properties of principal neurons in different LEC layers in postnatal rats. Using in vitro whole cell current-clamp recordings from up to four post hoc morphologically identified neurons simultaneously, we established that principal neurons show layer specific physiological and morphological properties, similar to those reported previously in adults. Principal neurons in L(ayer) I, LII, and LIII have the majority of their dendrites and axonal collaterals alone in superficial layers. LV contains mainly pyramidal neurons with dendrites and axons extending throughout all layers. A minority of LV and all principal neurons in LVI are neurons with dendrites confined to deep layers and axons in superficial and deep layers. Physiologically, input resistances and time constants of LII neurons are lower and shorter, respectively, than those observed in LV neurons. Fifty-four percent of LII neurons have sag potentials, resonance properties, and rebounds at the offset of hyperpolarizing current injection, whereas LIII and LVI neurons do not have any of these. LV neurons show prominent spike-frequency adaptation and a decrease in spike amplitudes in response to strong depolarization. Despite the well-developed interlaminar communication in LEC, the laminar differences in the biophysical and morphological properties of neurons suggest that their in vivo firing patterns and functions differ, similar to what is known for neurons in different MEC layers.
外侧缰状回皮层（LEC）向海马结构提供了主要的皮质输入，与内侧缰状回皮层（MEC）相当。为了了解 LEC 的功能贡献，需要了解内在网络中单个神经元的基础知识。本研究的目的是比较不同 LEC 层中出生后大鼠的主要神经元的生理和形态特性。通过体外全细胞电流钳记录，我们同时对多达四个后形态学鉴定的神经元进行了记录，结果表明主要神经元表现出与先前在成人中报道的相似的层特异性生理和形态特性。LEC 中的 L(ayer) I、LII 和 LIII 的主要神经元的树突和轴突突仅在浅层中。LV 主要包含具有树突和轴突延伸到所有层的金字塔形神经元。少数 LV 和所有 LVI 中的主要神经元是树突局限于深层且轴突在浅层和深层的神经元。在生理上，LII 神经元的输入电阻和时间常数分别低于 LV 神经元。54%的 LII 神经元具有 sag 电位、共振特性和在去极化电流注入结束时的反弹，而 LIII 和 LVI 神经元则没有这些特性。LV 神经元表现出明显的尖峰频率适应和在强去极化时尖峰幅度的降低。尽管 LEC 中存在发达的层间通讯，但神经元的生物物理和形态特性的分层差异表明它们在体内的放电模式和功能不同，这与不同 MEC 层中的神经元是相似的。
