Hormonal Factors and Recruitment of Neurons into the Stress Response Circuitry

在性成熟期间，大脑中启动发育和行为变化的机制仍有待阐明。我们假设，决定性别和性成熟的激素因素也直接募集神经元进入行为回路。应激反应回路中的果蝇多巴胺（DA）神经元可以作为解释这些因素的模型。在哺乳动物中，DA是应激反应途径的组成部分，DA调节类似的行为，并且DA的生物合成途径和再摄取机制高度保守。如果在性成熟和性成熟的雄性和雌性果蝇大脑的应激反应回路中招募了独特的DA神经元亚群，我们可以预测暴露于压力后DA调节行为的差异。DA神经元群是立体特异性的，数量有限，因此可以映射每个回路中独特的单个DA神经元。第一个目的是测试雄性和雌性果蝇的应激反应回路是否由独特的DA神经元亚群组成。我们已经用具有不同脑解剖缺陷的突变菌株确定了对应激反应至关重要的脑区域，并将通过免疫组织化学方法将其神经元DA模式与野生型进行比较，确定受每种突变影响的单个DA神经元。利用转基因和遗传工具靶向抑制DA合成，可以降低这些神经元中的DA水平。在性不成熟和成熟的雄性和雌性中，与正常反应的偏差将识别不同种群中独特的应激反应回路的单个DA神经元。然后，我们将测试DA神经元进入应激回路是否受到调节性分化和性成熟的因素的影响。虽然DA神经元的数量不是两性二态的，但在雄性和雌性中，进入反应回路的DA神经元是不同的。如果对应激反应至关重要的神经元被适当靶向，那么雄性果蝇的神经元亚群雌性化应该会改变应激反应。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神经元周围激素环境的影响可以使用药理学工具进行评估。本应用程序中提出的实验将确定在性分化和性成熟过程中被招募到应激反应回路中的特定DA神经元，并开始识别影响单个神经元招募的激素介质。这将为哺乳动物应激回路的发育和组织建模提供一种独特而创新的方法。

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.