Calcium Current Development and the Control of Spontaneous Activity in the Neonatal Mouse Brain

自发的电活动在神经系统发育中起着核心作用，有助于控制神经元如何迁移，使突触相互连接，并发展其产生适合其成熟功能的电信号的能力。在神经系统发育过程中，自发活动是如何产生的，人们知之甚少。目前的项目源于去年发现的一种惊人的自发电活动形式，在小鼠出生时的大脑皮层。脑钙片成像方法显示，在出生当天（P0）皮层神经元产生细胞内钙浓度（[Ca2+]i瞬态）的自发瞬态增加，这在非常大的神经细胞群中是高度同步的。这些[Ca2+]i瞬态是由电活动引起的，并且在所有皮层层和区域的60-80%的皮质神经元中同步发生。这个活动几乎只在出生的那一天出现。这种活动的开始似乎是由Na+电流密度的大量增加所调节的，而活动的停止则是由静息电导的大量增加所调节的。该项目研究了电压门控Ca2+电流在这种自发活动中允许Ca2+离子进入神经元中的作用。Ca2+是自发活动执行其发育功能的机制的第一步，[Ca2+]i瞬态的频率和Ca2+进入细胞的确切离子通道是至关重要的参数。最近的实验表明，在P0附近的皮质神经元中，总Ca2+电流密度急剧增加，这表明Ca2+电流的发展与活动是协调的。膜片钳和Ca2+成像方法将用于确定P0皮质神经元中存在哪些Ca2+通道亚型，它们在围产期的发育模式是什么，以及它们是否以及在多大程度上参与Ca2+进入导致自发活动期间的[Ca2+]i瞬变。知识价值。这些实验将阐明皮质神经元的内在离子通道特性，以及这些通道的发育模式，如何帮助形成大脑中对发育至关重要的自发活动。该实验室率先发现了大脑皮层的这种活动，并绘制了导致这种活动的离子通道发育图。该实验室还开展了广泛的离子通道发育和自发活动在无脊椎动物和两栖动物制剂中的作用的前期研究。Ca2+在自发活动期间进入神经元的机制是电活动如何在神经系统发育中发挥重要作用的主要决定因素。更广泛的影响。除了从根本上增加我们对神经系统发育的理解之外，这个项目将在一个特别适合整合研究和本科教育的环境中进行。作为本科生神经生物学专业的主任，穆迪博士经常在自己的实验室为本科生研究人员提供建议。事实上，老鼠皮层自发活动的发现就是由一个这样的本科生发现的，她在最近的神经科学学会会议上发表了她的发现。另一位刚刚进入实验室的本科生正在进行皮层神经元中Ca2+电流发展的实验。在本专业入门课程的教学中，实验室的研究作为神经元生物物理和发育研究的一个范例被带入课堂。

Spontaneous electrical activity plays central roles in nervous system development, helping to control how neurons migrate, make synaptic connections with one another, and develop their ability to generate electrical signals appropriate for their mature functions. How spontaneous activity is generated during nervous system development is only poorly understood.The present project results from the discovery in the last year of a striking form of spontaneous electrical activity in the mouse cerebral cortex near the time of birth. Brain slice calcium imaging methods revealed that on the day of birth (P0) neurons of the cortex generate spontaneous transient increases in intracellular calcium concentration ([Ca2+]i transients) that are highly synchronized across very large populations of nerve cells. These [Ca2+]i transients result from electrical activity, and occur synchronously in 60-80% of all cortical neurons in all cortical layers and regions. This activity is seen almost exclusively on the day of birth. The onset of this activity just before birth seems to be regulated by a large increase in Na+ current density, and the cessation of activity by a large increase in resting conductance just after P0.This project investigates the role of voltage-gated Ca2+ currents in admitting Ca2+ ions into the neurons during this spontaneous activity. Ca2+ is first step in the mechanism by which spontaneous activity carries out its developmental functions, and both the frequency of [Ca2+]i transients and the exact ion channels through which Ca2+ enters the cell are crucial parameters. The recent experiments have shown that there is a dramatic increase in total Ca2+ current density in cortical neurons near P0, suggesting that Ca2+ current development is coordinated with the activity. Patch clamp and Ca2+ imaging methods will be used to determine what Ca2+ channel subtypes are present in cortical neurons at P0, what the patterns of their development in the perinatal period are, and whether and to what extent they participate in Ca2+ entry leading to [Ca2+]i transients during spontaneous activity.Intellectual merit. These experiments will elucidate how the intrinsic ion channel properties of cortical neurons, and the patterns of development of those channels, help shape developmentally critical spontaneous activity in the brain. The laboratory is one of the first to discover such activity in cortex, and to map the ion channel development leading up to it. The laboratory has also carried out extensive prior studies of ion channel development and the roles of spontaneous activity in invertebrate and amphibian preparations. The mechanism by which Ca2+ enters neurons during spontaneous activity is a primary determinant of how electrical activity carries out its important roles in nervous system development.Broader impacts. In addition to adding fundamentally to our understanding of nervous system development, this project will occur in an environment particularly suited to integrating research and undergraduate education. As director of the undergraduate Neurobiology Major, Dr. Moody regularly advises undergraduate researchers in his own laboratory. In fact, the discovery of spnontaneous activity in mouse cortex was made by one such undergraduate, who presented her findings at the most recent Society for Neuroscience meeting. Experiments on Ca2+ current development in cortical neurons are being carried out by another undergraduate who has just started in the lab. In teaching the introductory course in the major, The Lab's research is brought into the classroom as an example of integrating biophysical and developmental studies of neurons.