Development of the Gustatory Solitary Nucleus

描述（由申请人提供）：脑干中孤束核（rNST）的吻侧部分是第一个中枢味觉中继。rNST接收来自面神经和舌咽神经的初级传入投射，所述面神经和舌咽神经支配舌味蕾和乳头，并在反映外周组织的地形中集中终止。rNST细胞增殖和分化的时间进程和分子因素还不清楚。考虑到味觉系统的正常功能的重要性，长期的目标是确定rNST是如何在胚胎大鼠中建立的。拟议的研究目标是确定：孤束（ST）的发展预测;的发展时间过程中的细胞成分的增殖和分化，包括rNST;的生物物理特性和突触的rNST神经元的发展;特定的分子因子存在于rNST的发展;和，操纵这些因素的表达，以确定对rNST的发展的影响。免疫荧光将用于确定神经元和神经胶质细胞的发育的时间进程，组成rNST分期胚胎。体外脑干切片制备将用于确定神经元功能的发育。免疫组织化学和蛋白质印迹方法将被用来确定的表达的Sonic刺猬（Shh）信号传导因子可能重要的增殖和分化的NST，和细胞周期调节跨发育阶段。最后，将使用外植体培养系统来分离脑干并在体外操纵定位于rNST和周围的Shh信号分子。工作的假设是，在胚胎发育过程中，神经前体细胞从第四脑室迁移和分化，形成最早的rNST，神经元分化神经胶质细胞之前，rNST神经元是功能性的，但与不断变化的属性，在胚胎中，和，Shh信号调节rNST神经前体细胞的增殖和分化的时间和新兴的神经生理功能在rNST。这些实验的结果将提供一个早期建立，组织和功能的rNST的理解，并将展示可能的分子途径参与该发展。这将为理解味觉系统初级传入中继的形成提供重要的基础，并为理解胚胎发育过程中发生环境操纵时在此中继中发生的可塑性奠定基础。此外，该提案解决了中枢神经系统神经模式化过程中的基本问题。公共卫生相关性：味觉是所有脊椎动物的营养选择和摄食行为的向导，由外周感受器转导并直接传递到脑干，在那里它与孤束吻侧核（rNST）中的其他感觉输入整合。了解孤核内接受这种感觉输入的神经元和胶质细胞的初始发育将有助于更全面地了解味觉信息如何整合到中枢神经系统中，以告知饮食选择，这是一种对维持生命很重要的行为。确定如何以及何时出现在rNST功能，并在分子水平上进行调节将是必不可少的，在理解可塑性的味觉系统。由于动物出生时必须进食，因此rNST必须具有指导初始营养摄入的功能。因此，重要的是要表征控制rNST正常发育的因素，以了解母亲的饮食，饮酒和药物如何影响rNST的神经发育和突触发生。

DESCRIPTION (provided by applicant): The rostral portion of the nucleus of the solitary tract (rNST) in the brainstem is the first central taste relay. The rNST receives primary afferent projections from facial and glossopharyngeal nerves, which innervate lingual taste buds and papillae and terminate centrally in a topography that reflects peripheral organization. The time course for and molecular factors involved in proliferation and differentiation of rNST cells are not well understood. Given the importance of an organized taste system for proper function, the long-term objective is to determine how the rNST is established in embryonic rat. The proposed research aims are to determine: the development of solitary tract (ST) projections; the developmental time course of proliferation and differentiation of cell components comprising the rNST; the development of biophysical properties and synapses of rNST neurons; specific molecular factors present in relation to rNST development; and, to manipulate the expression of these factors to determine effects on rNST development. Immunofluorescence will be used to identify the time course for development of neurons and glia that compose the rNST in staged embryos. An in vitro brainstem slice preparation will be used to determine development of neuron function. Immunohistochemical and Western blot approaches will be used to identify the expression of Sonic hedgehog (Shh) signaling factors potentially important for proliferation and differentiation in the NST, and cell cycle regulators across developmental stages. Finally, an explant culture system will be used to isolate the brainstem and manipulate in vitro Shh signaling molecules localized to the rNST and surround. The working hypotheses are that during embryonic development, neural precursors migrate from the fourth ventricle and differentiate to form the earliest rNST, where neurons differentiate before glia; that rNST neurons are functional, but with changing properties, in the embryo; and, that Shh signaling regulates the timing of proliferation and differentiation of rNST neural precursors and emerging neurophysiological function in rNST. Results of these experiments will provide an understanding of the early establishment, organization and function of the rNST and will demonstrate possible molecular pathways involved in that development. This will provide an important foundation for understanding the formation of the primary afferent relay of the gustatory system and lay the groundwork for understanding the demonstrated plasticity that occurs in this relay when environmental manipulations take place during embryogenesis. Furthermore, the proposal addresses essential questions in the process of neural patterning in the CNS. PUBLIC HEALTH RELEVANCE: Taste sensation, which guides nutritive choices and ingestive behaviors of all vertebrates, is transduced by peripheral receptors and conveyed directly to the brainstem where it is integrated with other sensory inputs in the rostral nucleus of the solitary tract (rNST). Knowledge of initial development of neurons and glia within the solitary nucleus that receive this sensory input will contribute to a more complete understanding of how taste information is integrated in the central nervous system to inform diet choices, a behavior important to sustain life. Determining how and when function emerges in rNST and is regulated at a molecular level will be essential in understanding plasticity of the taste system. Because animals have to feed at birth, the rNST must be functional to guide initial nutrient intake. It is therefore important to characterize factors controlling normal development of rNST to understand how maternal diet, alcohol consumption and drugs can influence neural development and synaptogenesis of the rNST.