Two Types of Monoamine Oxidase

描述（由申请人提供）：本申请的目的是验证以下假设：1)早期发育阶段对单胺氧化酶（MAO） A通过调节5-羟色胺（5-羟色胺，5-HT）水平和前脑区域5-HT受体的激活诱导神经可塑性和攻击性的长期影响至关重要；2)环境应激与MAO A相互作用，调节这些过程。MAO A是5-HT代谢的关键酶，其缺乏导致人类和小鼠5-HT水平升高和攻击性增强。前脑区域（额叶皮质、杏仁核和海马）中的5-羟色胺调节攻击性以及锥体神经元的树突和脊柱形态。具体目的概述如下：1：确定5-HT对MAO A敲除（KO）小鼠额叶皮质、杏仁核和海马锥体神经元的攻击性、树突形态和脊柱密度的影响在哪个早期发育阶段至关重要。在前脑5- ht神经支配（E16-P28）的5周内，每次给MAO A KO小鼠注射5- ht合成抑制剂对氯苯丙氨酸（PCPA），以使前脑区域升高的5- ht水平正常化。用高效液相色谱法测定5-羟色胺水平。攻击和其他相关行为将在成年小鼠中进行测试（P60）。一旦我们确定了5-HT在行为中作用的关键阶段，我们将使用高尔基-考克斯染色脑切片的光学显微镜以及具有5-HT受体标记和树突过程逆行标记的切片的荧光显微镜研究前脑区域5-HT靶向锥体神经元的树突和脊柱形态。2：探讨5-HT受体介导的5-HT对MAO A KO小鼠关键发育阶段前脑攻击和树突形态的影响。在关键阶段用PCPA治疗MAO A KO小鼠后，我们将通过RT-PCR定量其前脑区域的5-HT1A， 5-HT1B和5-HT2A受体（mRNA水平）。为了研究每种受体在行为和形态中的作用，我们将在特定的关键阶段给MAO A KO小鼠注射特定5-HT受体的选择性拮抗剂，并确定哪种受体阻断会减弱P60的攻击和形态改变。3：验证MAO A与急性或慢性环境应激的相互作用诱导前脑区域5-HT特异性变化，从而导致攻击行为增加，改变树突和脊柱形态的假设。我们将研究急性和慢性约束应激对MAO A KO小鼠行为和脑形态的影响。这些研究将对基础和临床研究作出重大贡献，阐明发育机制和压力对攻击的影响，并阐明针对攻击和其他精神疾病（包括酗酒和吸毒）的新的预防和治疗战略。

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.