Calcium Waves in Pyramidal Neurons

描述(申请人提供)：海马区锥体神经元突触后[Ca~(2+)]i的变化在诱导各种形式的突触可塑性、基因表达和调节膜电导方面发挥重要作用。所有这些机制都可以影响这些神经元在涉及学习和记忆的电路中的行为。因此，对这些过程的详细了解对于了解大脑功能是重要的。在锥体神经元中，有三个明显的钙来源可以被海马区的突触机制激活：通过NMDA受体的钙进入，通过电压依赖的钙通道进入，以及从内库释放钙。我们将研究通过激活锥体细胞的IP3受体和ryanodine受体，从SD大鼠海马区CA1区脑片中释放的钙的性质和功能。第一组实验将检验在这些神经元的主要树突中新发现的自发基本事件的性质。这些局部事件可以被膜电位和mGluR介导的突触传递所调节，并且它们本身可能具有重要的信号功能。第二组实验将检查斜树突体和轴突中这些事件的性质。以前的实验证实，这些区域没有发现钙释放波，可能是从这些事件中建立起来的。我们将试图了解波的受限空间分布和更广泛的基本事件分布。这些事件的位置和时间进程将用高速成像和双光子显微镜进行检查。突触传递的刺激将辅以细胞外谷氨酸和卡巴胆碱以及细胞内IP3和Ca~(2+)的定位，以实现信号事件在粗细树突状区域的精确定位。我们将研究钙离子在几个重要的生理过程中的作用，特别是不同树突区域钙离子释放的不同后果。其中一组实验将研究钙离子释放在细胞兴奋性可塑性诱导中的作用。第二组实验将研究钙波在抑制内源性大麻素介导的锥体神经元突触抑制中的作用。 与公共健康相关：该项目将研究锥体神经元内库突触激活的钙释放的性质和功能。有关这种钙来源的信息可能与理解大脑回路中的可塑性变化有关，因此对于理解学习和记忆的细胞机制也很重要。这些过程中的缺陷被认为与包括阿尔茨海默病、精神分裂症和抑郁症在内的几种病理状况有关。

DESCRIPTION (provided by applicant): Postsynaptic [Ca2+]i changes in pyramidal neurons in the hippocampus play an important role in the induction of various forms of synaptic plasticity, gene expression, and modulation of membrane conductances. All of these mechanisms can affect the behavior of these neurons in circuits involved in learning and memory. Therefore, a detailed understanding of these processes is important for understanding brain function. There are three clear sources of Ca2+ in pyramidal neurons that can be activated by synaptic mechanisms in the hippocampus: Ca2+ entry through NMDA receptors, entry through voltage-dependent Ca2+ channels, and Ca2+ release from internal stores. We will investigate the properties and functions of Ca2+ released from stores mediated by activation of IP3 receptors and ryanodine receptors in pyramidal cells in slices from the CA1 region of the hippocampus in Sprague Dawley rats. The first set of experiments will examine the properties of newly discovered spontaneous elementary events in the main dendrites of these neurons. These local events can be modulated by membrane potential and mGluR mediated synaptic transmission and could have important signaling functions by themselves. The second set of experiments will examine the properties of these events in the oblique dendrites, soma, and axon. Previous experiments established that Ca2+ release waves, which are probably built from these events, are not found in these regions. We will try to understand the restricted spatial distribution of waves and more widespread distribution of elementary events. The location and time course of these events will be examined with high speed imaging and 2-photon microscopy. Stimulation with synaptic transmission will be supplemented with focal uncaging of extracellular glutamate and carbachol and intracellular IP3 and Ca2+ to achieve precise localization of signaling events in thick or thin dendritic regions. We will investigate the function of Ca2+ released from stores in several important physiological processes, with particular emphasis on the different consequences of Ca2+ released in different dendritic regions. One set of experiments will examine the role of Ca2+ release in the induction of plasticity of cell excitability. A second set of experiments will examine the role of the Ca2+ waves in suppressing synaptic inhibition onto pyramidal neurons mediated by endogenous cannabinoids. PUBLIC HEALTH RELEVANCE: This project will examine the properties and function of synaptically activated calcium release from internal stores in pyramidal neurons. Information about this source of calcium could be relevant for understanding plastic changes in brain circuits and therefore important for understanding the cellular mechanisms underlying learning and memory. Defects in these processes have been implicated in several pathological conditions including Alzheimer's disease, schizophrenia and depression.