Walsh Darren A, Brown Jonathan T, Randall Andrew D
Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Hatherly Laboratory, Exeter, UK.
School of Clinical Sciences, University of Bristol, Bristol, UK.
J Physiol. 2017 Jun 1;595(11):3549-3572. doi: 10.1113/JP273915. Epub 2017 Apr 25.
The nucleus reuniens (Re), a nucleus of the midline thalamus, is part of a cognitive network including the hippocampus and the medial prefrontal cortex. To date, very few studies have examined the electrophysiological properties of Re neurons at a cellular level. The majority of Re neurons exhibit spontaneous action potential firing at rest. This is independent of classical amino-acid mediated synaptic transmission. When driven by various forms of depolarizing current stimulus, Re neurons display considerable diversity in their firing patterns. As a result of the presence of a low threshold Ca channel, spike output functions are strongly modulated by the prestimulus membrane potential. Finally, we describe a novel form of activity-dependant intrinsic plasticity that eliminates the high-frequency burst firing present in many Re neurons. These results provide a comprehensive summary of the intrinsic electrophysiological properties of Re neurons allowing us to better consider the role of the Re in cognitive processes.
The nucleus reuniens (Re) is the largest of the midline thalamic nuclei. We have performed a detailed neurophysiological characterization of neurons in the rostral Re of brain slices prepared from adult male mice. At resting potential (-63.7 ± 0.6 mV), ∼90% of Re neurons fired action potentials, typically continuously at ∼8 Hz. Although Re neurons experience a significant spontaneous barrage of fast, amino-acid-mediate synaptic transmission, this was not predominantly responsible for spontaneous spiking because firing persisted in the presence of glutamate and GABA receptor antagonists. With resting potential preset to -80 mV, -20 pA current injections revealed a mean input resistance of 615 MΩ and a mean time constant of 38 ms. Following cessation of this stimulus, a significant rebound potential was seen that was sometimes sufficiently large to trigger a short burst of very high frequency (100-300 Hz) firing. In most cells, short (2 ms), strong (2 nA) current injections elicited a single spike followed by a large afterdepolarizing potential which, when suprathreshold, generated high-frequency spiking. Similarly, in the majority of cells preset at -80 mV, 500 ms depolarizing current injections to cells led to a brief initial burst of very high-frequency firing, although this was lost when cells were preset at -72 mV. Biophysical and pharmacological experiments indicate a prominent role for T-type Ca channels in the high-frequency bursting of Re neurons. Finally, we describe a novel form of activity-dependent intrinsic plasticity that persistently eliminates the burst firing potential of Re neurons.
reunien核（Re）是丘脑中线的一个核团，是包括海马体和内侧前额叶皮质在内的认知网络的一部分。迄今为止，很少有研究在细胞水平上研究Re神经元的电生理特性。大多数Re神经元在静息时表现出自发动作电位发放。这与经典的氨基酸介导的突触传递无关。当受到各种形式的去极化电流刺激驱动时，Re神经元的放电模式表现出相当大的多样性。由于存在低阈值钙通道，动作电位输出功能受到刺激前膜电位的强烈调节。最后，我们描述了一种新的活动依赖性内在可塑性形式，它消除了许多Re神经元中存在的高频爆发式放电。这些结果全面总结了Re神经元的内在电生理特性，使我们能够更好地考虑Re在认知过程中的作用。
reunien核（Re）是丘脑中线最大的核团。我们对成年雄性小鼠制备的脑片 Rostral Re中的神经元进行了详细的神经生理学特征分析。在静息电位（-63.7±0.6 mV）时，约90%的Re神经元发放动作电位，通常以约8 Hz的频率持续发放。尽管Re神经元经历了大量快速的、氨基酸介导的自发突触传递，但这并不是自发放电的主要原因，因为在存在谷氨酸和GABA受体拮抗剂的情况下仍持续放电。将静息电位预设为-80 mV，20 pA的电流注入显示平均输入电阻为615 MΩ，平均时间常数为38 ms。在该刺激停止后，观察到明显的反弹电位，有时该电位足够大，足以触发一段非常高频（100-300 Hz）的短脉冲发放。在大多数细胞中，短（2 ms）、强（2 nA）的电流注入引发单个动作电位，随后是一个大的后去极化电位，当超过阈值时，产生高频放电。同样，在大多数预设为-80 mV的细胞中，向细胞注入500 ms的去极化电流会导致短暂的初始高频放电爆发，尽管当细胞预设为-72 mV时这种放电会消失。生物物理和药理学实验表明T型钙通道在Re神经元的高频爆发中起重要作用。最后，我们描述了一种新的活动依赖性内在可塑性形式，它持续消除Re神经元的爆发式放电电位。
