Comparative developmental neurobiology of molluscs and zebrafish

神经系统的发育和进化起源通常不清楚。例如，在不同动物的生命中，第一个神经元是什么时候发育出来的？这些细胞的功能是什么？在不同的动物群体中，单个神经元或神经回路能否被识别出来？如果是这样的话，哪些细胞和回路的特征在动物之间是一致的，哪些特征的变化允许进化变化？我们建议通过关注3种不同的神经回路来回答这些问题，这些神经回路可以根据保守的神经递质含量和发育细节来识别。1)软体动物幼体感觉功能相关的神经元。在软体动物幼虫中发育的第一批细胞中，有一些含有神经递质血清素。这些细胞似乎是感觉和控制纤毛参与进食和运动。此外，在其他海洋无脊椎动物幼虫中也可以识别出类似的细胞，从而表明共同的进化起源（即，同源性）。我们建议扩大目录的幼虫细胞含有其他已知的发射机通过检查组胺，氨基丁酸（GABA），乙酰胆碱和可能的谷氨酸盐的分布，这一切似乎发挥作用的化学感觉和平衡感在成年软体动物，但尚未被研究在发展中的软体动物或其他海洋幼虫。然而，我们假设，发射器特异性标签将允许识别在动物王国中广泛存在的同源神经元，并且这些同源物的识别将为神经系统的早期进化提供新的见解。2)斑马鱼的嗅觉通路。我们以前研究了感觉神经元轴突进入嗅球时是如何组织的。我们接下来将集中在嗅球内的中间神经元的发展，其中含有GABA和多巴胺，并在整个脊椎动物中发现。3)斑马鱼的心内神经系统。通过释放乙酰胆碱和去甲肾上腺素来控制心脏的自主神经通路的解剖学现在在鱼类中得到了很好的描述，并且与控制哺乳动物心脏的那些惊人地相似。接下来，我们将试图研究这些途径的个体发育，并深入了解它们何时开始发挥作用。

The developmental and evolutionary origins of the nervous system are generally unclear. When, for example, do the first neurons develop in the lives of different animals? What are the functions of these cells? Can individual neurons or neural circuits be recognized between different groups of animals? If so, which features of the cells and circuits are consistent between animals and which ones vary to permit evolutionary change? We proposed to answer such questions by focusing on 3 different neural circuits that can be recognized on the bases of conserved neurotransmitter contents and details of development. 1) Larval neurons related to sensory functions in molluscs. Some of the very first cells to develop in molluscan larvae contain the neurotransmitter serotonin. These cells appear to be sensory and to control cilia involved in feeding and locomotion. Furthermore, similar cells can be recognized in other marine invertebrate larvae, thus suggesting common evolutionary origins (i.e., homology). We propose to expand the catalogue of larval cells containing other known transmitters by examining the distributions of histamine, -amino butyric acid (GABA), acetylcholine and possibly glutamate which all appear to play roles in chemosensation and the sense of balance in adult molluscs but have not yet been studied in developing molluscs or other marine larvae. We hypothesize, however, that transmitter-specific labels will permit the identification of homologous neurons that are widespread in the animal kingdom, and identification of these homologues will provide new insights into the early evolution of nervous systems. 2) Olfactory pathways in zebrafish. We have previously studied the development of how axons of sensory neurons are organized as they enter the olfactory bulb. We will next concentrate on the development of interneurons within the olfactory bulb which contain on GABA and dopamine and are found throughout the vertebrates. 3) Intracardiac nervous system in zebrafish. The anatomy of autonomic pathways controlling the heart through the release of acetylcholine and norepinephrine are now well described in fish and are strikingly similar with those controlling the hearts of mammals. We will next seek to examine the ontogeny of those pathways and gain insights into when they first become functional.