Hormonal Factors and Recruitment of Neurons into the Stress Response Circuitry

在性成熟期间启动大脑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荷尔蒙因素也直接将神经元招募到行为回路中。应激反应回路中的果蝇多巴胺(DA)神经元可以作为阐明这些因素的模型。对于哺乳动物来说，DA是应激反应途径中不可或缺的一部分，DA调节类似的行为，DA的生物合成途径和再摄取机制是高度保守的。如果性未成熟和成熟的雄性和雌性果蝇大脑中独特的DA神经元亚群被招募到应激反应电路中，我们预测在暴露于应激后DA调节行为的差异。DA神经元群是立体特异性的，数量有限，因此人们可以定位每个回路唯一的单个DA神经元。第一个目的是测试应激反应回路是否由性未成熟和成熟的雄性和雌性果蝇中独特的DA神经元亚群组成。我们已经使用具有明显解剖缺陷的突变株确定了对应激反应至关重要的大脑区域，并将通过免疫组织化学比较其神经元DA模式与野生型来确定受每个突变影响的单个DA神经元。通过使用转基因和遗传工具定向抑制DA合成，这些神经元中的DA水平将会降低。在性不成熟和成熟的男性和女性中，对正常反应的偏离将识别出不同人群中应激反应回路所独有的个别DA神经元。然后，我们将测试DA神经元的招募是否会受到调节性分化和性成熟的因素的影响。虽然DA神经元的数量不是性别二态的，但被招募到反应回路中的DA神经元在男性和女性中是不同的。如果对应激反应至关重要的神经元得到了适当的靶向，那么雌雄果蝇的神经元亚群的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神经元周围荷尔蒙环境的影响可以用药理学工具进行评估。本申请中提出的实验将识别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，并启动影响单个神经元招募的激素介质的识别。这将提供一种独特和创新的方法来模拟哺乳动物应力回路的发展和组织。

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.