Mechanisms and functions of dendritic dopamine release in the brain

大脑中使用化学信使多巴胺（DA）的神经元在控制运动，动机行为和认知方面起着关键作用。目前，我们对大脑中控制DA释放的基本机制知之甚少。虽然DA从神经元的神经末梢（轴突末梢）释放被充分表征并且已知通过调节的胞吐作用的形式发生，但DA也从DA神经元的细胞体和树突释放（STD DA释放），并且目前对这如何发生以及它在脑功能中起什么作用知之甚少。这项综合研究计划可能会导致更好地了解DA神经元在运动，动机和认知中的作用。它还将确定一种可能与解释大脑其他化学信使（如血清素和神经肽）的树突释放有关的机制。我们对STD DA释放的作用知之甚少，主要是因为目前还没有方法选择性地阻断或增强STD DA的释放来检查功能和行为后果，STD DA释放强烈减少或阻断的小鼠模型的开发将代表该领域的重大进展。我们计划在我们最近的体外发现的基础上建立这样的小鼠模型。我们将解决以下两个具体目标：* 具体目标1：确定STD DA释放的机制。我们将在我们最近的发现基础上，使用培养的DA神经元，表明钙敏感蛋白synaptotagmin 4和synaptotagmin 7是STD DA的关键决定因素。我们将检测小鼠脑切片中的DA释放，以验证DA神经元中synaptotagmin 4和/或synaptotagmin 7的缺失将严重减少STD DA释放的假设。*具体目标#2：确定STD DA释放的功能和行为作用。我们将建立在目标1的实验基础上，以获得对STD DA释放在脑功能和脑功能中的作用的第一个见解。由于推测的负反馈作用的STD DA释放，我们假设，在STD DA释放的情况下，DA神经元的电活动将增加。我们还假设DA神经元的连接强度将被改变。最后，我们将对这些STD DA释放减少的小鼠进行彻底的行为评估，以确定STD DA释放在调节行为中的一些主要作用。我们假设运动、动机行为和空间工作记忆将会改变。**

Neurons in the brain that use the chemical messenger dopamine (DA) play a key role in the control of movement, motivated behaviors and cognition. At present, we know very little about the basic mechanisms that control DA release in the brain. Although DA release from the neurons' nerve endings (axon terminals) is well characterized and known to occur through a form of regulated exocytosis, DA is also released from the cell body and dendrites of DA neurons (STD DA release) and very little is presently known about how this occurs and what roles it plays in brain function. This integrated research program may lead to a better understanding of the role of DA neurons in movement, motivation and cognition. It will also identify a mechanism that is likely to be relevant to explain the dendritic release of other chemical messengers of the brain such as serotonin and neuropeptides. The reason we know so little about the roles of STD DA release is mainly because at the present time, there is no way to selectively block or enhance STD DA release to examine the functional and behavioral consequences.The development of a mouse model in which STD DA release is strongly reduced or blocked would represent a major advance in the field. We plan to build on our recent in vitro discoveries to establish such a mouse model.***We will address the following two specific aims:***Specific aim #1 : Identification of the mechanism of STD DA release. We will build on our recent discovery using DA neurons maintained in culture showing that the calcium-sensing proteins synaptotagmin 4 and synaptotagmin 7 are critical determinants of STD DA. We will detect DA release in mouse brain sections to test the hypothesis that deletion of synaptotagmin 4 and/or synaptotagmin 7 in DA neurons will severely reduce STD DA release.***Specific aim #2 : Identification of the functional and behavioral roles of STD DA release. We will build on our experiments from aim 1 to obtain the first insights into the roles of STD DA release in brain function and behavor. Due to a presumed negative feedback role of STD DA release, we hypothesize that in the absence of STD DA release, the electrical activity of DA neurons will be increased. We also hypothesize that the strength of connections onto DA neurons will be altered. Finally, we will perform a thorough behavioral evaluation of these mice in which STD DA release has been reduced to identify some of the major roles of STD DA release in regulating behavior. We hypothesize that movement, motivated behaviors and spatial working memory will be altered.**