Călin Alexandru, Waseem Tatiana, Raimondo Joseph V, Newey Sarah E, Akerman Colin J
Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK.
Division of Cell Biology, Department of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa.
iScience. 2023 Mar 9;26(4):106363. doi: 10.1016/j.isci.2023.106363. eCollection 2023 Apr 21.
Intracellular chloride and pH play fundamental roles in determining a neuron's synaptic inhibition and excitability. Yet it has been difficult to measure changes in these ions during periods of heightened network activity, such as occur in epilepsy. Here we develop a version of the fluorescent reporter, ClopHensorN, to enable simultaneous quantification of chloride and pH in genetically defined neurons during epileptiform activity. We compare pyramidal neurons to the major GABAergic interneuron subtypes in the mouse hippocampus, which express parvalbumin (PV), somatostatin (SST), or vasoactive intestinal polypeptide (VIP). Interneuron populations exhibit higher baseline chloride, with PV interneurons exhibiting the highest levels. During an epileptiform discharge, however, all subtypes converge upon a common elevated chloride level. Concurrent with these dynamics, epileptiform activity leads to different degrees of intracellular acidification, which reflect baseline pH. Thus, a new optical tool for dissociating chloride and pH reveals neuron-specific ion dynamics during heightened network activity.
细胞内氯离子和pH值在决定神经元的突触抑制和兴奋性方面起着基本作用。然而，在网络活动增强的时期，如癫痫发作时，很难测量这些离子的变化。在这里，我们开发了一种荧光报告基因ClopHensorN的变体，以便在癫痫样活动期间对基因定义的神经元中的氯离子和pH值进行同时定量。我们将小鼠海马体中的锥体神经元与主要的γ-氨基丁酸能中间神经元亚型进行比较，这些亚型表达小白蛋白（PV）、生长抑素（SST）或血管活性肠肽（VIP）。中间神经元群体表现出较高的基线氯离子水平，其中PV中间神经元的水平最高。然而，在癫痫样放电期间，所有亚型的氯离子水平都会升高到一个共同的水平。与这些动态变化同时发生的是，癫痫样活动会导致不同程度的细胞内酸化，这反映了基线pH值。因此，一种用于分离氯离子和pH值的新型光学工具揭示了网络活动增强期间神经元特异性的离子动态变化。
