PHYSIOLOGY OF DORSAL COCHLEAR NUCLEUS MOLECULAR LAYER

中枢听觉信息处理的第一阶段 系统是由神经回路和膜介导的 耳蜗核细胞的特性。一个细分的区域 耳蜗核，即耳蜗背核(DCN)，具有 特别是复杂的内部架构，以及 DCN中的细胞对声刺激的响应基本上被修改 从他们的八分之一的神经输入。在这个最肤浅的层面 核，一个由细小的无髓平行纤维组成的系统(轴突 颗粒细胞。)在主体上制造无数的突触 DCN(锥体细胞)和小细胞的投射神经元 中间神经元(手轮细胞和星状细胞)。平行纤维 为一套独特而广泛的 与音调轴垂直的相互作用 DCN.平行光纤系统很可能扮演着重要的角色 在形成复杂感受野和时间的过程中的作用 DCN锥体细胞的反应模式。 为了了解颗粒细胞和它们之间的关联 局部电路可以影响锥体细胞，我们正在研究 电刺激颗粒轴突的反应 细胞，平行的纤维。这项提案中的实验 调查平行光纤影响的四个具体方面 DCN神经元在体外脑片制备中和在 活着。首先，细胞外和细胞内的记录将从 用单个DCN神经元研究平行纤维的突触反应 刺激。在细胞内记录之后，神经元将 染色后用于形态鉴定。回应将是 与细胞类型和板层位置相关。第二，当前 将使用源=密度分析来确定空间和 产生的电流汇和源的时间分布 软脑膜表面平行纤维的电刺激 原子核。这一分析将揭示层流分布。 平行纤维与DCN之间的突触联系 神经元。第三，突触前后的机制影响 平行纤维突触的突触增强将是 探索过了。增强的时间进程将被确定。 第四，兴奋性突触传递的药理学 从平行纤维到它们的突触后靶点，还有 可能存在可被激活的抑制性氨基酸局部回路 由DCN分子层中的平行纤维组成，将 调查过了。 这些研究的结果将提供重要的信息 并行光纤系统在DCN中的作用，并将有助于 产生关于这个系统所扮演的角色的新理论 处理传入的声学信息。这些实验将 还为随后对 可能作为外周功能发生的中枢生理学 声创伤和老化，以及对 DCN神经元的突触可塑性和膜生物物理学。

The first stage of information processing in the central auditory system is mediated by the neural circuits and membrane properties of cells in the cochlear nucleus. One subdivision of the cochlear nucleus, the dorsal cochlear nucleus (DCN), has a particularly complex internal architecture, and the responses of cells in the DCN to acoustic stimuli are substantially modified from their eights nerve inputs. In most superficial layer of this nucleus, a system of fine unmyelinated parallel fibers (axons of granule cells.) make numerous synapses upon the principal projection neurons of the DCN (pyramidal cells) and small interneurons (cartwheel and stellate cells). The parallel fibers provide the substrate for a unique and extensive set of interactions occurring orthogonal to the tonotopic axis of the DCN. It is likely that the parallel fiber system plays an important role in shaping the complex receptive fields and temporal response patterns of the DCN pyramidal cells. In order to understand how the granule cells and their associated local circuitry can influence pyramidal cells, we are studying responses to electrical stimulation of the axons of the granule cells, the parallel fibers. The experiments in this proposal investigate four specific aspects of parallel fiber influences on DCN neurons both in an in vitro brain slice preparation, and in vivo. First, extra- and intracellular recordings will be made from single DCN neurons to study synaptic responses to parallel fiber stimulation. Subsequent to intracellular recordings, neurons will be stained for morphological identification. Responses will be correlated with cell type and laminar position. Second, current source=density analysis will be used to determine the spatial and temporal distribution of current sinks and sources produced by electrical stimulation of the parallel fibers at the pial surface of the nucleus. This analysis will reveal the laminar distribution of synaptic connections between the parallel fibers and DCN neurons. Third, pre- and post-synaptic mechanisms influencing synaptic potentiation at the parallel fiber synapse will be explored. The time course of potentiation will be determined. Fourth, the pharmacology of excitatory synaptic transmission from parallel fibers to their postsynaptic targets, and also of possible inhibitory amino-acid local circuits that can be activated by parallel fibers in the DCN molecular layer, will be investigated. The results of these studies will provide important information on the role of the parallel fiber system in the DCN, and will help generate new theories about the role that this system plays in processing incoming acoustic information. These experiments will also set the stage for subsequent investigations of changes in central physiology that may occur as a function of peripheral acoustic trauma and aging, as well as investigations of the synaptic plasticity and membrane biophysics of DCN neurons.