Two Types of Monoamine Oxidase

描述(由申请人提供)：本申请的目的是检验如下假设：1)早期发育阶段对单胺氧化酶(MAO)A至关重要，单胺氧化酶A通过调节5-羟色胺(5-羟色胺，5-HT)水平和激活前脑区域的5-HT受体，对神经可塑性和攻击性产生长期影响；以及2)环境应激与MAO A相互作用，调节这些过程。单胺氧化酶A是5-羟色胺代谢的关键酶，它的缺乏会导致5-羟色胺水平升高，增加人和小鼠的攻击性。前脑区域(额叶皮质、杏仁核和海马区)的5-羟色胺调节攻击行为以及锥体神经元的树突和棘突的形态。具体目标概括如下：1：确定5-羟色胺对MAO A基因敲除(KO)小鼠额叶皮质、杏仁核和海马区锥体神经元的攻击行为和树突形态及棘突密度的影响在哪些早期发育阶段是关键的。在前脑5-羟色胺神经支配(E16-P28)的5周期间，MAO A KO小鼠将注射5-羟色胺合成抑制剂对氯苯丙氨酸(PCPA)，以使其前脑区升高的5-羟色胺水平正常化。5-羟色胺水平将用高效液相色谱法测定。攻击性和其他相关行为将在成年小鼠身上进行测试(P60)。一旦我们确定了5-羟色胺在行为中作用的关键阶段，我们将使用高尔基-考克斯染色的脑切片上的光学显微镜以及带有5-羟色胺受体标记和树突逆行标记的切片上的荧光显微镜来研究前脑区5-羟色胺靶向锥体神经元的树突和棘突的形态。2.探讨5-羟色胺受体在MAO-A-KO小鼠发育关键时期对攻击行为和前脑区树突形态的影响。在用PCPA治疗处于关键阶段的MAO A KO小鼠后，我们将用RT-PCR方法对其前脑区的5-HT1A、5-HT1B和5-HT2A受体(mRNA水平)进行定量。为了研究每个受体在行为和形态中的作用，我们将在特定的关键阶段向MAO A KO小鼠注射特定的5-羟色胺受体的选择性拮抗剂，并确定哪种受体拮抗剂可以减轻P60的攻击和形态变化。3.验证MAO A与急、慢性环境应激相互作用引起前脑区5-羟色胺(5-HT)特异性改变，导致攻击性增强，树突棘形态改变的假说。我们将研究急性和慢性束缚应激对MAO A KO小鼠行为和脑形态的影响。这些研究将通过阐明发育机制和压力对攻击性的影响，为基础和临床研究做出重大贡献，并阐明针对攻击性和包括酒精和药物滥用在内的其他精神疾病的新的预防和治疗策略。 公共卫生相关性这项应用将研究单胺氧化酶(MAO)A在关键发育阶段和特定前脑区域对5-羟色胺水平、脑形态以及攻击性和相关情绪行为的调节作用。还将研究MAO A与环境胁迫的相互作用及其对这些现象的影响。这项研究将为理解攻击性的分子基础和大脑回路提供至关重要的发现。它还将为与异常单胺类神经传递相关的攻击性和其他精神障碍的预防、诊断和治疗战略提供新的线索。

DESCRIPTION (provided by applicant): The objective of this application is to test the hypothesis that: 1) early developmental stages are critically important for monoamine oxidase (MAO) A to induce long-term effects on neuroplasticity and aggression through the regulation of serotonin (5-hydroxytryptamine, 5-HT) levels and the activation of 5-HT receptors in forebrain regions; and 2) environmental stress interacts with MAO A to modulate these processes. MAO A is the key enzyme in 5-HT metabolism, and its deficiency results in increased 5-HT levels and increased aggression in humans and mice. 5-HT in forebrain regions (frontal cortex, amygdala and hippocampus) modulates aggression as well as dendrite and spine morphology in pyramidal neurons. The specific aims are outlined below: 1: To identify which early developmental stages are critical for the effects of 5-HT on aggression and dendritic morphology and spine density in pyramidal neurons of frontal cortex, amygdala and hippocampus in MAO A knockout (KO) mice. MAO A KO mice will be injected with the 5-HT synthesis inhibitor p-chlorophenylalanine (PCPA) during each of the 5 weeks of forebrain 5-HT innervation (E16-P28), to normalize the increased 5-HT levels in their forebrain regions. 5-HT levels will be determined by HPLC. Aggression and other related behaviors will be tested in adult mice (P60). Once we identify the critical stage for 5-HT role in behavior, we will study dendrite and spine morphology of 5-HT-targeted pyramidal neurons in forebrain regions, using light microscopy on Golgi-Cox stained brain sections as well as fluorescence microscopy on sections with 5-HT receptor labels and retrograde label of dendritic processes. 2: To identify what 5-HT receptors mediate the effects of 5-HT on aggression and dendritic morphology in forebrain regions of MAO A KO mice during the critical developmental stages. After treating MAO A KO mice with PCPA at the critical stages, we will quantify 5-HT1A, 5-HT1B and 5-HT2A receptors (mRNA levels) in their forebrain regions by RT-PCR. To study the role of each receptor in behavior and morphology, we will inject MAO A KO mice with selective antagonists of specific 5-HT receptors during the specific critical stages, and determine which receptor blockade attenuates aggression and morphological alterations at P60. 3: To test the hypothesis that the interaction between MAO A and acute or chronic environmental stress induces specific changes in 5-HT in forebrain regions, which result in increased aggression and altered dendrite and spine morphology. We will study the impact of acute and chronic restraint stress on the behavior and brain morphology of MAO A KO mice. These studies will provide a significant contribution to basic and clinical research, by elucidating the impact of developmental mechanisms and stress on aggression, and shed light on new preventive and therapeutic strategies for aggression and other psychiatric disorders, including alcohol and drug abuse. PUBLIC HEALTH RELEVANCE This application will study the role of monoamine oxidase (MAO) A during critical developmental stages and in specific forebrain regions on the regulation of serotonin levels, brain morphology and aggressive and related emotional behaviors. The interaction between MAO A and environmental stress and its impact on these phenomena will also be studied. This research will provide critically important findings for the understanding of the molecular basis and the brain circuitry of aggression. It will also shed new light on preventive, diagnostic and therapeutic strategies for aggression and other mental disorders associated with abnormal monoamine neurotransmission.