Glutamate release at inhibitory synapses in developing auditory system

描述（由申请人提供）：本研究的长期目标是了解哺乳动物大脑发育中听觉回路建立和功能优化的规则和机制。提出的实验旨在提供更多关于抑制性声音定位途径的机制，即从梯形体内侧核（MNTB）到外侧上橄榄（LSO）的甘氨酸能途径在地形上变得精细。先前的研究表明，在地形细化期间，发育中的MNTB-LSO通路中的单个突触不仅释放抑制性神经递质甘氨酸和GABA，还释放兴奋性递质谷氨酸。拟议应用的具体目的是(a)研究谷氨酸共释放和突触后谷氨酸受体如何促进LSO树突突触后钙反应的产生，以及(b)检验MNTB-LSO突触根据其功能性神经递质表型在亚细胞水平上组织的假设。利用双光子钙成像和应用于新生小鼠脑干切片的全细胞膜片钳记录的组合来解决这些目标。这些实验的结果对于更好地理解正常和异常听觉回路的发育非常重要，从而可能为人类交流障碍的生物学基础提供见解，例如语言障碍和阅读障碍，这些被认为是由异常发育引起的。未成熟脑回路的解剖和功能微调是听力正常发展的重要里程碑。建议研究计划应用最先进的生理技术来研究小鼠声音定位回路中神经元通讯的机制。这些研究的结果可以更好地理解包括语言障碍和阅读障碍在内的听觉障碍的生物学基础，最终可以找到减轻或治疗这些障碍的新策略。

DESCRIPTION (provided by applicant): The long term goal of this research is to provide understanding of the rules and mechanisms by which auditory circuits in the developing mammalian brain become established and functionally optimized. Proposed experiments are aimed to provide more insight into the mechanisms by which an inhibitory sound localization pathway, the glycinergic pathway from the medial nucleus of the trapezoid body (MNTB) to the lateral superior olive (LSO) becomes topographically refined. Previous studies demonstrated that, during the period of topographic refinement, individual synapses in the developing MNTB-LSO pathway not only release the inhibitory neurotransmitters glycine and GABA, but also release the excitatory transmitter glutamate. The specific aims of the proposed application are (a) to investigate how glutamate co-release and postsynaptic glutamate receptors contribute to the generation of postsynaptic calcium responses in LSO dendrites, and (b) test the hypothesis that MNTB-LSO synapses are organized on a subcellular level according to their functional neurotransmitter phenotype. These aims are addressed using a combination of 2-photon calcium imaging and whole-cell patch clamp recordings applied to brainstem slices from neonatal mice. The results from proposed experiments will be important for better understanding normal and abnormal auditory circuit development and thus may provide insights into the biological basis of human communication disorders, such as language disabilities and dyslexia that are thought to arise from abnormal development. Summery in lay language: Anatomical and functional fine-tuning of immature brain circuits are important milestones for the normal development of hearing. Proposed research plans to apply state-of-the-art physiological techniques to investigate mechanism of neuronal communication in a mouse sound localization circuit. Results from these studies may provide better understanding of the biological basis that underlie auditory disorders including language disabilities and dyslexia which ultimately can lead to new strategies of alleviating or curing these disabilities.