Two Types of Monoamine Oxidase

描述（由申请人提供）：本申请的目的是检验以下假设：1）早期发育阶段对于单胺氧化酶（MAO）A通过调节5-羟色胺诱导对神经可塑性和攻击性的长期影响至关重要（5-羟色胺，5-HT）水平和前脑区5-HT受体的激活; 2）环境胁迫与单胺氧化酶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，它的缺乏会导致人类和小鼠5-羟色胺水平的增加和攻击性的增加。前脑区域（额叶皮质、杏仁核和海马）中的5-HT调节攻击性以及锥体神经元中的树突和棘形态。具体目标概述如下：1：确定哪些早期发育阶段是5-HT对MAOA基因敲除（KO）小鼠的攻击性以及额叶皮质、杏仁核和海马锥体神经元中树突形态和棘密度的影响的关键。在前脑5-HT神经支配（E16-P28）的5周中的每一周期间，用5-HT合成抑制剂对氯苯丙氨酸（PCPA）注射MAOA KO小鼠，以使其前脑区域中增加的5-HT水平正常化。将通过HPLC测定5-HT水平。将在成年小鼠中测试攻击性和其他相关行为（P60）。一旦我们确定了5-HT在行为中作用的关键阶段，我们将研究前脑区域中5-HT靶向锥体神经元的树突和棘形态，使用Golgi-Cox染色脑切片上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上的荧光显微镜。第二章：确定在关键发育阶段，5-HT对MAOA KO小鼠前脑区域的攻击性和树突形态的影响是由哪些5-HT受体介导的。在关键阶段用PCPA处理MAO A KO小鼠后，我们将通过RT-PCR定量其前脑区域中的5-HT 1A、5-HT 1B和5-HT 2A受体（mRNA水平）。为了研究每种受体在行为和形态学中的作用，我们将在特定的关键阶段给MAO A KO小鼠注射特异性5-HT受体的选择性拮抗剂，并确定哪种受体阻断剂在P60时减弱攻击性和形态学改变。第三节：为了验证以下假设，即MAO A与急性或慢性环境应激之间的相互作用诱导前脑区域中5-HT的特异性变化，这导致攻击性增加以及树突和棘形态改变。我们将研究急性和慢性束缚应激对MAO A KO小鼠行为和脑形态学的影响。这些研究将通过阐明发展机制和压力对攻击性的影响，为基础和临床研究作出重大贡献，并阐明攻击性和其他精神疾病，包括酗酒和吸毒的新的预防和治疗战略。 公共卫生相关性本申请将研究单胺氧化酶（MAO）A在关键发育阶段和特定前脑区域对5-羟色胺水平、大脑形态和攻击性及相关情绪行为的调节作用。此外，还将研究单胺氧化酶A与环境胁迫之间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。它还将为与单胺神经传递异常相关的攻击性和其他精神障碍的预防、诊断和治疗策略提供新的思路。

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.