Hormonal Factors and Recruitment of Neurons into the Stress Response Circuitry

在性成熟过程中，大脑中启动发育和行为变化的机制仍有待阐明。我们推测，参与决定性别和性成熟的激素因素也直接招募神经元进入行为回路。果蝇的多巴胺（DA）神经元的压力反应电路可以作为一个模型，阐明这些因素。对于哺乳动物，DA是应激反应途径的组成部分，DA调节类似的行为，并且DA生物合成途径和再摄取机制高度保守。如果在性不成熟和成熟的雄性和雌性果蝇的大脑中，DA神经元的独特子集被招募到应激反应回路中，我们预测暴露于应激后DA调制行为的差异。DA神经元群体是立体特异性的并且数量有限，因此可以映射每个回路特有的单个DA神经元。第一个目的是测试是否压力反应电路是由性不成熟和成熟的男性和女性果蝇的DA神经元的独特的子集。我们已经确定了大脑区域的应激反应的关键突变株与不同的解剖学脑缺陷，并将确定个别DA神经元的神经元DA模式与野生型的免疫组化比较，每个突变的影响。通过使用转基因和遗传工具靶向敲低DA合成，将降低这些神经元中的DA水平。性不成熟和成熟的男性和女性的正常反应的偏差将确定在不同的人群中的压力反应电路独特的个别DA神经元。然后，我们将测试是否招募DA神经元进入压力电路的影响因素，调节性分化和性成熟。虽然DA神经元的人口是不是两性异形，DA神经元招募到反应电路不同的男性和女性。雌性化的神经元的子集，否则雄性苍蝇应改变应激反应，如果神经元的反应的关键已被适当的目标。促性腺激素的作用影响应激反应以及神经元的分化和重组。DA神经元周围的激素环境的影响可以使用药理学工具进行评估。本申请中提出的实验将鉴定在性分化和性成熟期间发生的被招募到应激反应回路中的特定DA神经元，并开始鉴定影响个体神经元招募的激素介质。这将提供一个独特的和创新的方法来模拟哺乳动物的压力电路的发展和组织。

The mechanisms initiating developmental and behavioral changes in the brain during sexual maturity remain to be elucidated. We hypothesize that hormonal factors involved in determination of sex and sexual maturity also direct recruitment of neurons into behavioral circuits. The Drosophila dopamine (DA) neurons within the stress response circuitry can serve as a model in which to elucidate these factors. As for mammals, DA is integral to the stress response pathway, DA modulates analogous behaviors, and the DA biosynthetic pathways and reuptake mechanisms are highly conserved. If unique subsets of DA neurons are recruited into the stress response circuitry in the brains of sexually immature and mature male and female Drosophila, we predict differences in DA-modulated behaviors after exposure to stress. The DA neuronal population is stereospecific and limited in number, so one can map individual DA neurons unique to each circuit. The first aim tests whether the stress response circuitry is composed of unique subsets of DA neurons in sexually immature and mature male and female Drosophila. We have identified brain regions critical for the stress response using mutant strains with distinct anatomical brain defects and will identify the individual DA neurons affected by each mutation by immunohistochemical comparisons of their neuronal DA patterns with wild type. DA levels will be decreased in those neurons by targeted knockdown of DA synthesis using transgenic and genetic tools. Deviations from the normal response in sexually immature and mature male and females will identify the individual DA neurons unique to the stress response circuitry in the different populations. We will then test whether recruitment of DA neurons into the stress circuitry is influenced by factors that regulate sexual differentiation and sexual maturity. While the population of DA neurons is not sexually dimorphic, DA neurons recruited into the response circuits differ in males and females. Feminization of subsets of neurons in an otherwise male fly should alter the stress response if neurons critical for the response have been appropriately targeted. The actions of gonadotropic hormones affect the stress response as well as neuronal differentiation and reorganization. The impact of the hormonal environment surrounding the DA neurons can be assessed using pharmacological tools. The experiments proposed in this application will identify the specific DA neurons recruited into the stress response circuitry that occur during sexual differentiation and sexual maturity, and initiate identification of hormonal mediators affecting recruitment of individual neurons. This will provide a unique and innovative approach to modeling the development and organization of the stress circuitry in mammals.