EXCITATORY AMINO ACID TRANSMITTERS IN CNS

谷氨酸被广泛认为是最显著的兴奋性物质 哺乳动物中枢神经系统使用的神经递质。这 Project使用了大鼠大脑的海马体结构作为测试 研究谷氨酸作用机制的系统 变速箱。目前的建议集中在三个突触前 机制：自身受体对释放过程的调节，改变 二十烷类化合物的产生和参与的释放过程 脯氨酸的含量。最近的研究表明，谷氨酸/天冬氨酸的释放可以 通过激活NMDA受体增强，通过激活抑制 ACPD或AP4代谢性受体。这些机制由 这些形式的自动监管是如何运作的，目前还不清楚。切片 而海马区CA1区的突触小体准备将用于 解决这个问题。这些制剂释放谷氨酸和 以依赖于钙离子的方式从外源性末端合成天冬氨酸 Schaffer侧支-连合-同侧联合通路。 这些兴奋性氨基酸的释放将在 不同作用方式对CA1突触体除极作用的研究 作用机制(K+，4-氨基吡啶、藜芦碱升高)。并行的 实验：终末去极化、[Ca~(2+)]i与突触小泡 将测量自行车骑行量。通过研究受体配体对基因表达的影响 这些措施，将有可能确定一些细胞 涉及自动调节的过程。二十碳二烯酸(花生四烯酸和 其代谢物)在以下过程中大量产生和释放 神经病理状态，它们可能介导NMDA受体- 托尔依赖的释放增强作用。从CA1释放的二十烷基类化合物 NMDA受体激活期间的区域将被识别，其可能 参与NMDA受体介导的自动调节将被评估和 它们对释放过程的影响将被确定。最后，一个 将开发一种方法来激发和定量谷氨酸的释放 和天冬氨酸在体外兴奋性刺激下的CA1区 传入纤维。这一方法将被用来确定生理上的 和/或病理条件下自身受体调节 可检测到谷氨酸/天冬氨酸的释放。脯氨酸是一种兴奋性物质 和兴奋毒性亚氨基酸，可以阻止记忆的形成。 依赖于Na+的高亲和力摄取的Pro由一个子集表达 谷氨酸途径。这些性质认为，脯氨酸起到了 在兴奋性传输中。谷氨酸合成与释放的研究进展 并将进行兴奋性突触传递来阐明 这个角色。一个重要的工具将是针对 克隆传送器的推定运输地点。来自这些的发现 研究将与神经疾病的治疗相关， 例如癫痫，它涉及到海马体的过度活动 儿童癫痫的形成以及相关的病因 伴有高脯氨酸血症。它们也可能被证明与突触有关 记忆和学习的机制。

Glutamate is widely acknowledged as the most prominent excitatory neurotransmitter used by the mammalian central nervous system. This project employs the hippocampal formation of the rat brain as a test system with which to investigate the mechanisms of glutamate transmission. The present proposal focuses on three presynaptic mechanisms: autoreceptor regulation of the release process, alterations of the release process due to eicosanoid production and the involvement of proline. Recent work suggests that glutamate/aspartate release can be enhanced by activation of the NMDA receptor and depressed by activation of either the ACPD or the AP4 metabotropic receptor. The mechanisms by which these forms of autoregulation operate are not understood. Slice and synaptosomal preparations of hippocampal area CA1 will be used to address this problem. These preparations release both glutamate and aspartate in a Ca2+-dependent manner from terminals of the extrinsic Schaffer collateral-commissural-ipsilateral associational pathway. Release of these excitatory amino acids will be quantitated during depolarization of CA1 synaptosomes with agents that work by different mechanisms (elevated K+, 4-aminopyridine, veratridine). In parallel experiments, terminal depolarization, [Ca2+]i and synaptic vesicle cycling will be measured. By studying the effects of receptor ligands on these measures, it will be possible to determine some of the cellular processes involved in autoregulation. Eicosanoids (arachidonic acid and its metabolites) are produced and released in large amounts during neuropathological states, and they may mediate the NMDA recep- tor-dependent enhancement of release. Eicosanoids released from the CA1 area during NMDA receptor activation will be identified, their possible involvement in NMDA receptor-mediated autoregulation will be assessed and their effects on the release process will be determined. Finally, a method will be developed to evoke and quantitate the release of glutamate and aspartate from area CA1 in vitro by stimulation of excitatory afferent fibers. This method will be used to determine the physiological and/or pathological conditions under which autoreceptor regulation of glutamate/aspartate release can be detected. Proline is an excitatory and excitotoxic imino acid that can block memory formation. Na+-dependent, high affinity uptake of proline is expressed by a subset of glutamate pathways. These properties argue that proline plays a role in excitatory transmission. Studies of glutamate synthesis and release and of excitatory synaptic transmission will be carried out to elucidate this role. An important tool will be antibodies directed against the presumed transport site of the cloned transporter. Findings from these studies will be relevant to the treatment of neurological conditions, such as epilepsy, which involve hyperactivity of the hippocampal formation, as well as to the etiology of childhood seizures associated with hyperprolinemia. They may also prove relevant to synaptic mechanisms of memory and learning.