RUI: Development and Maturation of Olfactory Centers in the Lobster: Influences of Serotonin and Adult Neurogenesis

Beltz0091092这些研究的主要目标是通过体内和体外方法了解5-羟色胺、一氧化氮和终生神经发生如何对嗅觉通路的发展和维持做出贡献。龙虾Homarus americanus被用作实验系统，因为从早期胚胎发育起，就存在着支配嗅觉区域的巨大的5-羟色胺能神经元，而且嗅觉通路中的神经发生贯穿动物的整个生命。以往的研究表明，5-羟色胺影响新生嗅觉中间神经元的增殖，并促进嗅觉投射神经元的分支。此外，新生投射神经元在出生后的头几个小时内会短暂地吸收5-羟色胺。我们目前的研究有四个特定的目的：1.利用阻断5-羟色胺转运体的药理学药物来确定由新生嗅觉投射神经元瞬时摄取5-羟色胺所介导的功能，同时测试对嗅觉间神经元的增殖和生长的影响。2.对龙虾的初步研究表明，一氧化氮(NO)在嗅觉通路的发育和维持中也可能起着重要作用。NO系统将通过免疫细胞化学方法检测大脑中一氧化氮合酶的时间和空间调节来定义。此外，将通过实验改变NO水平，以测试对嗅觉中间神经元神经发生速度的影响。3.将建立一个体外系统来检验我们在体内研究中出现的假说。本研究的目的是为了成功地培养嗅觉中间神经元，以便进行三个主要的实验：与5-羟色胺能背巨细胞共培养嗅觉投射神经元，在投射神经元培养中引入5-羟色胺以观察对分支的影响，以及有可能直接操纵NO/cGMP通路并观察培养的投射神经元是否不敏感。4.对我们关于神经发生在嗅觉中心的发育和维持中的重要性的假设的一个检验，是在甲壳类物种中观察这些问题，这些物种具有决定性的生长和限定的寿命。因此，我们将询问这些物种在终末蜕皮之前和之后的嗅觉区域是否有持续的增殖。这些研究与高等生物的发育机制有关，因为嗅觉通路的组织和加工之间有许多相似之处，即使在系统发育上相距遥远的物种中也是如此。此外，这些研究正在探索涉及神经回路发展和维护的基本机制，这可能适用于其他系统的频谱。

Beltz0091092The primary goals of these studies are to understand how serotonin, nitric oxide and life-long neurogenesis contribute to the development and maintenance of the olfactory pathway, using in vivo and in vitro methods. The lobster Homarus americanus is used as the experimental system because of the presence of giant serotonergic neurons that innervate the olfactory areas from early embryonic development, and because neurogenesis in the olfactory pathway persists throughout the animal's life. Prior studies have shown that serotonin influences the proliferation of newborn olfactory interneurons and promotes the branching of olfactory projection neurons. Additionally, newborn projection neurons transiently take up serotonin within the first few hours after their birth. There are 4 specific aims of our current studies: 1. The functions that are mediated by the transient serotonin uptake into newborn olfactory projection neurons will be defined using pharmacological agents that block the serotonin transporter, while testing for effects on proliferation and outgrowth of the olfactory interneurons. 2. Preliminary studies in the lobster suggest that nitric oxide (NO) also may be important in the development and maintenance of the olfactory pathway. The NO system will be defined by examining the temporal and spatial regulation of NOS in the brain using immunocytochemical methods. Further, NO levels will be altered experimentally in order to test for effects on the rate of neurogenesis among olfactory interneurons. 3. An in vitro system will be established to test hypotheses emerging from our in vivo studies. The goal of this effort is to successfully culture olfactory interneurons in order to perform three major experiments: to co-culture olfactory projection neurons with the serotonergic dorsal giant neuron, to introduce serotonin into cultures of projection neurons in order to visualize effects on branching, and to have the potential to directly manipulate the NO/cGMP pathway and observe whether cultured projection neurons are NO sensitive. 4. One test for our hypotheses regarding the importance of neurogenesis in the development and maintenance of olfactory centers, is to look at these issues in crustacean species that have determinate growth and a defined lifespan. We will therefore ask whether there is persistent proliferation in the olfactory areas of these species before, and then after, a terminal molt. These studies are relevant to developmental mechanisms in higher organisms because there are many parallels between the organization of olfactory pathways and processing even in phylogenetically distant species. In addition, these studies are exploring basic mechanisms involved in the development and maintenance of neural circuits, which may be applicable in a spectrum of other systems.