Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science , Bangalore 560 012, India ; Undergraduate program, Indian Institute of Science , Bangalore 560 012, India.
Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science , Bangalore 560 012, India.
eNeuro. 2015 Aug 31;2(4). doi: 10.1523/ENEURO.0053-15.2015. eCollection 2015 Jul-Aug.
How do neurons reconcile the maintenance of calcium homeostasis with perpetual switches in patterns of afferent activity? Here, we assessed state-dependent evolution of calcium homeostasis in a population of hippocampal pyramidal neuron models, through an adaptation of a recent study on stomatogastric ganglion neurons. Calcium homeostasis was set to emerge through cell-autonomous updates to 12 ionic conductances, responding to different types of synaptically driven afferent activity. We first assessed the impact of theta-frequency inputs on the evolution of ionic conductances toward maintenance of calcium homeostasis. Although calcium homeostasis emerged efficaciously across all models in the population, disparate changes in ionic conductances that mediated this emergence resulted in variable plasticity to several intrinsic properties, also manifesting as significant differences in firing responses across models. Assessing the sensitivity of this form of plasticity, we noted that intrinsic neuronal properties and the firing response were sensitive to the target calcium concentration and to the strength and frequency of afferent activity. Next, we studied the evolution of calcium homeostasis when afferent activity was switched, in different temporal sequences, between two behaviorally distinct types of activity: theta-frequency inputs and sharp-wave ripples riding on largely silent periods. We found that the conductance values, intrinsic properties, and firing response of neurons exhibited differential robustness to an intervening switch in the type of afferent activity. These results unveil critical dissociations between different forms of homeostasis, and call for a systematic evaluation of the impact of state-dependent switches in afferent activity on neuronal intrinsic properties during neural coding and homeostasis.
神经元如何在传入活动模式的持续转换中协调钙稳态的维持？在这里，我们通过对咀嚼神经元的最新研究进行改编，评估了海马锥体神经元模型群体中钙稳态的状态相关演变。钙稳态是通过 12 种离子电导的细胞自主更新来实现的，以响应不同类型的突触驱动传入活动。我们首先评估了θ频率输入对离子电导向钙稳态维持的演变的影响。尽管钙稳态在群体中的所有模型中都有效地出现，但介导这种出现的离子电导的不同变化导致了多种内在特性的可变可塑性，这也表现为模型之间的发射反应存在显著差异。评估这种形式可塑性的敏感性时，我们注意到内在神经元特性和发射反应对目标钙浓度以及传入活动的强度和频率敏感。接下来，当传入活动在两种行为上明显不同的活动类型（θ频率输入和主要处于静默期的尖峰波涟漪）之间以不同的时间序列切换时，我们研究了钙稳态的演变。我们发现神经元的电导值、内在特性和发射反应对传入活动类型的干预性切换表现出不同的稳健性。这些结果揭示了不同形式的稳态之间的关键差异，并呼吁系统评估传入活动的状态相关切换对神经编码和稳态期间神经元内在特性的影响。
