NEW NEURONS AND NEW SYNAPSES

这项建议描述了对新增加的 神经元和由此产生的突触连接性的重组 发生在硬骨鱼的胚胎后生长期间。重点放在两个方面 主要主题：视网膜细胞结构的改变 杆状和球果的个体发育差异及其部位的变化 生长中的视顶盖中单个视网膜纤维的终止。 有三个具体目标。1)描述…的人口特征 不同大小的金鱼中的光感受器，尤其是关于 在生长中的视网膜中杆状物质的积累，并确定是否 随着年龄的增长，个体光感受器的结构也会发生变化。2.)至 确定产生新杆状细胞的祖细胞。这些分裂 细胞位于外核层，在成熟的杆状核之间； 它们只能用胸腺嘧啶核苷放射自显影来鉴定，但已经 在超微结构研究中从未被描述过。杆子的作用 祖细胞将在正常的视网膜中进行评估(它们是否仅增加了 杆状种群还是它们的一些后代取代了失去的杆状 通过细胞死亡？)在再生的视网膜中(他们是否能够 在这种情况下产生视杆细胞以外的视网膜神经元？)这个 杆状祖细胞的个体发育历史将在幼虫中进行研究 视网膜来确定这些独特的细胞来自哪里。3.)要绘制图表， 单个视网膜终末随时间变化的断层位置 持久的神经解剖学标记。因为视网膜和顶盖一起生长 不等同的维度，有人认为系统性的转变 发生在视网膜顶盖地图上，而这一假设将是 测试过。硬骨鱼感光器发育的解剖学研究 视网膜将提供有关视杆细胞和视锥细胞如何不同的信息 对于了解优先影响的疾病过程具有重要意义 特定的光感受器。对视网膜顶盖投射的分析可能 为突触连接的自然变化提供证据 这将有助于我们对发展和再生的理解 神经元连接。

This proposal describes an anatomical investigation of the addition of new neurons and the resultant reorganizations of synaptic connectivity which occur during postembryonic growth of teleost fish. The focus is on two principle topics: changes in retinal cytoarchitecture resulting from ontogenetic differences between rods and cones and changes in the sites of termination of individual retinal fibers in the growing optic tectum. There are three specific aims. 1.) To characterize the population of photoreceptors in goldfish of different sizes, especially with regard to the accumulation of rods in the growing retina, and to determine whether structural changes occur in individual photoreceptors with age. 2.) To identify the progenitor cells which generate new rods. These dividing cells are located in the outer nuclear layer, amongst mature rod nuclei; they have been identified only with thymidine radioautography but have never been described in ultrastructural studies. The role of rod progenitors will be assessed in the normal retina (do they only add to the rod population or are some of their progeny replacements for rods lost through cell death?) and in the regenerating retina (are they able to generate retinal neurons other than rods under those circumstances?). The ontogenetic history of rod progenitors will be investigated in larval retinas to determine where these unique cells come from. 3.) To chart the tectotopic positions of individual retinal terminals over time using long-lasting neuroanatomical markers. Because retina and tectum grow along non-equivalent dimensions, it has been suggested that systematic shifts occur in the retinotectal map, and it is this hypothesis which is to be tested. The anatomical studies of photoreceptor development in teleost retina will provide information about how rods and cones differ that may be significant for understanding disease processes which preferentially affect specific photoreceptors. The analysis of retinotectal projections may provide evidence for naturally-occuring changes in synaptic connectivity that would contribute to our understanding of development and regeneration of neuronal connections.