Calcium Waves in Pyramidal Neurons

描述（由申请人提供）：海马锥体神经元突触后[Ca2+]i的变化在诱导各种形式的突触可塑性、基因表达和膜电导调节中起重要作用。所有这些机制都可以影响这些神经元在学习和记忆回路中的行为。因此，详细了解这些过程对于理解大脑功能非常重要。锥体神经元中的Ca2+有三个明确的来源，可以通过海马突触机制激活：Ca2+通过NMDA受体进入，通过电压依赖性Ca2+通道进入，以及Ca2+从内部储存释放。我们将在Sprague Dawley大鼠海马CA1区的切片中研究由IP3受体和ryanodine受体激活介导的锥体细胞中Ca2+释放的特性和功能。第一组实验将检验这些神经元主树突中新发现的自发基本事件的性质。这些局部事件可通过膜电位和mGluR介导的突触传递调节，并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。先前的实验表明，Ca2+释放波可能是由这些事件形成的，但在这些区域没有发现。我们将设法了解波的有限空间分布和基本事件的更广泛分布。这些事件的位置和时间过程将用高速成像和双光子显微镜检查。突触传递刺激将辅以细胞外谷氨酸和碳水化合物以及细胞内IP3和Ca2+的局部释放，以实现在厚或薄树突区域的信号事件的精确定位。我们将研究Ca2+从商店释放在几个重要的生理过程中的功能，特别强调Ca2+在不同树突区域释放的不同后果。一组实验将检验Ca2+释放在诱导细胞兴奋性可塑性中的作用。第二组实验将研究Ca2+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。

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.