Organization and Function of the Extra-Bulbar Olfactory Pathway

神经系统的进化变化为理解神经系统和行为之间的关系提供了一个难得的机会。当新的大脑结构被创造出来时，这对一个有机体的行为有什么影响？这些新结构如何与神经系统的其他部分相互作用？我们正在用脊椎动物的嗅觉系统（负责嗅觉的系统）作为研究神经系统进化变化的模型。为此，我们正在探索各种脊椎动物嗅觉系统的组织。最近，科学家们发现，一些鱼类和两栖动物鼻子里的感受器细胞与前脑底部的a区相连，而不是像通常那样与嗅球相连。这个新发现的子系统，即“眼球外通路”，其结构尚不清楚，其功能也没有得到研究。在拟议的实验中，眼球外通路的受体细胞在鼻子内的位置将在成年蝾螈（Ambystoma mexicanum）中进行检查，蝾螈是一种终生生活在水中的蝾螈。本研究将采用单细胞电生理记录方法研究蝾螈球外信号通路的感受细胞对气味的反应特性。这些实验将使我们能够检查球外途径的功能，并验证一个有趣的假设，即球外途径在检测信息素中起作用。信息素是由动物产生的化学物质，它能将信息传递给同一物种的其他成员，告诉他们信息素产生者的性别或生殖状态。 这些实验将首次对球外通路的组织和功能提供清晰的描述。这项研究对我们理解气味信息在嗅觉感受器细胞中转化为电信号的方式，以及气味信息在嗅球中的处理方式具有重要意义，可能有助于阐明气味感知的神经机制。

Evolutionary changes in the nervous system offer a tremendousopportunity to understand the relationship between the nervous system andbehavior. When new brain structures are created, what does this do to anorganism's behavior? How do these new structures interact with otherportions of the nervous system? We are usingthe vertebrate olfactory system (the system responsible for the sense ofsmell) as a model for examining evolutionary changes in the nervous system.To this end, we are exploring the organization of the olfactory system ina variety of vertebrate animals. Recently, scientists have learned that receptor cells in the noseof some fishes and amphibians are connected to the a region in the base ofthe forebrain, instead of to the olfactory bulbs, as is usual for thesecells. The structure of this newly-discovered subsystem, the "extra-bulbarpathway," is poorly understood, and its function has not been investigated.In the proposed experiments, the location of the receptor cells of theextra-bulbar pathway within the nose will be examined in adult axolotls(Ambystoma mexicanum), a salamander species that lives in water throughoutits life. Single-cell electrophysiological recording methods will be usedto study the odorant response properties of the receptor cells of theextra-bulbar pathway in axolotls. These experiments will allow us toexamine the function of the extra-bulbar pathway, andto test an interesting hypothesis that suggests that the extra-bulbarpathway functions in detection of pheromones. Pheromones are chemicalsproduced by animals that carry information to other members of the samespecies to tell them about the producer's sex or reproductive status. These experiments will provide the first clear description of theorganization and function of the extra-bulbar pathway. This research hasimportant implications for our understanding of the ways in which odorantinformation is converted into electrical signals in olfactory receptorcells, as well as the way odorant information is processed in the olfactorybulbs, potentially shedding light on the neural mechanisms underlying odorperception.