Function-Specific Serotonergic Neurons and Body Temperature Regulation.

描述（由申请人提供）： 包括体温调节在内的稳态机制对于维持温血哺乳动物的生理平衡至关重要。涉及脑干、下丘脑、脊髓和外周的专门神经元回路调节热量的产生和消散过程，使体温保持在生理上可接受的狭窄窗口内，即使面对大的环境温度波动。脑干多巴胺能（5-HT）神经元包括这个温度调节网络的一个关键组成部分;有证据表明，它们通过与脊髓中的神经元突触来调节下游产热机制，脊髓中的神经元向外周投射以控制血管收缩、棕色脂肪代谢和颤抖反应。与以前的发现一致，我们实验室的工作已经通过直接实验手段（通过诱导性神经元沉默）建立了脑干5-HT神经元确实需要维持37 ℃的体温，即使在室温（23 ℃）下。此外，我们最近的功能和遗传研究表明，负责维持体温的5-HT神经元的关键子集来自发育中的后脑的菱体6-8（r6-8），并最终占据脑干中缝下部，因为沉默其他子集无法重现整个5-HT系统扰动后观察到的引人注目的温度表型。在这里，我们建议直接测试这个预测。利用我们实验室最近设计的交叉药物遗传学神经元沉默工具，以诱导和可逆地抑制离散5-HT神经元亚型的动作电位放电，我们将在一系列体温调节试验中扰乱清醒自由行为小鼠中的r6-8衍生的5-HT亚群（Aim 1）。然后，我们将确定沉默5-HT神经元亚群如何影响热量守恒和生成机制（目标2），我们将绘制这些神经元的下游神经支配目标，以更好地了解它们在体温调节中的作用（目标3）。参与体温调节的特定5-HT神经元亚型的鉴定和表征将促进我们对基本稳态机制的理解，我们对这些创新遗传工具的实施将为进一步研究这些对基本哺乳动物生存至关重要的神经元类型和电路打开大门。

DESCRIPTION (provided by applicant): Homeostatic mechanisms, including thermoregulation, are essential for maintaining physiologic balance in warm-blooded mammals. Specialized neuronal circuits involving the brainstem, hypothalamus, spinal cord, and periphery regulate heat generation and dissipation processes that keep body temperature within a narrow physiologically acceptable window, even in the face of large ambient temperature swings. Brainstem serotonergic (5-HT) neurons comprise one key component of this thermoregulatory network; evidence suggests that they modulate downstream thermogenic mechanisms by synapsing on neurons in the spinal cord that project peripherally to control vasoconstriction, brown fat metabolism and shivering responses. In line with previous findings, work in our lab has established by direct experimental means (via inducible neuronal silencing) that brainstem 5-HT neurons are indeed required for maintaining 37C body temperature, even at room temperature (23C). Further, our recent functional and genetic studies suggest that the critical subset of 5-HT neurons responsible for maintenance of body temperature derive from rhombomeres 6-8 (r6-8) of the developing hindbrain and ultimately populate the lower brainstem raphe, as silencing other subsets fails to reproduce the dramatic temperature phenotype observed upon perturbation of the entire 5-HT system. Here we propose to test this prediction directly. Utilizing an intersectional pharmacogenetic neuronal silencing tool recently engineered in our lab to inducibly and reversibly suppress action potential firing in discrete 5-HT neuron subtypes, we will perturb this r6-8-derived 5-HT subset in the awake freely behaving mouse in a series of thermoregulatory assays (Aim 1). We will then determine how silencing 5-HT neuron subsets impinges on heat conservation and generation machinery (Aim 2), and we will map the downstream innervation targets of these neurons to better understand their role in thermoregulation (Aim 3). The identification and characterization of the specific 5-HT neuron subtype that participates in body temperature modulation will advance our understanding of a fundamental homeostatic mechanism, and our implementation of these innovative genetic tools will open the door to further investigation of these neuron types and circuits which are so essential to basic mammalian survival.