EXCITATORY AMINO ACID TRANSMITTERS IN CNS

这个项目利用大鼠大脑的海马体结构来 研究谷氨酸的传递机制。目前的建议 重点阐述了脯氨酸在调节谷氨酸中的生理作用 传播学和高血压病的病理生理后果 在遗传性疾病中，脯氨酸浓度被称为高脯氨酸血症。 脯氨酸是一种兴奋性和兴奋性的亚氨基酸，可以阻断记忆 形成并导致逆行性失忆。此外，高脯氨酸血症 与儿童癫痫的发病率远高于正常水平有关 和智力低下。一种依赖Na+/Cl-的高亲和力转运蛋白 专一性的Pro-line是由谷氨酸的一个子集唯一表达的 小路。在人脑脊液的典型浓度下， 液体，在这样一种途径中增强传播：Schaffer 侧支-连合投射至CA1区。“脯氨酸诱导的 增强作用“是依赖于NMDA受体的，而且是持久的。 观察表明体内的一些谷氨酸突触是正常存在的 处于部分增强状态，这是由于连续占用 一小部分NMDA受体通过脯氨酸。机械结构的研究 脯氨酸诱导的增强将用场来进行 CA1锥体细胞的膜片钳记录。 具体目标包括确定在多大程度上由脯氨酸诱导 增强利用的机制与涉及的机制重叠 电诱发的长时程增强，无论低浓度的 Pro实际上在这些细胞中激发了可测量的NMDA电流，无论是 Pro诱导的突触增强既涉及突触前，也涉及突触后 机制，无论是突触后的AMPA和NMDA成分 反应是否增强，以及脯氨酸是否改变了对GABA的抑制。 另一组研究将考察脯氨酸转运体在 脯氨酸诱导的增强。目标是确定是否 必须摄取脯氨酸，才能产生增强作用或转运 只是用来调节局部胞外的脯氨酸浓度。 这些研究将利用以下发现：四肽甘氨酸- Gly-Phe-Leu对高亲和力脯氨酸的选择性抑制作用 运输和海马区的外侧和内侧部分 穿孔路径在摄取脯氨酸的能力上有明显的差异。一个 最后一项研究将探讨脯氨酸抑制的机制。 谷氨酸的释放。这一效应可以通过浓度的脯氨酸观察到 存在于脑脊液中的 II型高脯氨酸血症，但没有正常的脯氨酸浓度。 拟议研究的结果将阐明一种新的规则 谷氨酸传递可能是有吸引力的药物靶点 发展。它们也可能被证明与记忆的突触机制有关 和学习。

This project employs the hippocampal formation of the rat brain to investigate mechanisms of glutamate transmission. The present proposal focuses on the physiological role of proline in regulating glutamate transmission and on the pathophysiological consequences of elevated proline concentrations in the genetic disorders known as hyperprolinemia. Proline is an excitatory and excitotoxic imino acid that can block memory formation and induce retrograde amnesia. Moreover, hyperprolinemia is associated with a much higher than normal incidence of childhood seizures and mental retardation. A Na+/Cl--dependent, high affinity transporter specific for pro-line is expressed exclusively by a subset of glutamate pathways. Proline, at a concentration typical of human cerebrospinal fluid, potentiates transmission in one such pathway: the Schaffer collateral-commissural projection to area CA1. "Proline-induced potentiation" is NMDA receptor-dependent and long-lasting. These observations suggest that some glutamate synapses in vivo normally exist in a partially potentiated state due to the continuous occupation of a small fraction of NMDA receptors by proline. Mechanistic studies of proline-induced potentiation will be carried out with use of field potential and whole cell patch clamp recordings from CA1 pyramidal cells. Specific objectives include determining to what extent proline-induced potentiation utilizes mechanisms that overlap those involved in electrically-evoked long-term potentiation, whether low concentrations of proline actually evoke a measurable NMDA current in these cells, whether proline-induced potentiation involves presynaptic as well as postsynaptic mechanisms, whether both AMPA and NMDA components of the postsynaptic response are potentiated and whether proline modifies GABA inhibition. Another set of studies will examine the role of the proline transporter in proline-induced potentiation. The objective is to determine whether proline must be taken up for potentiation to occur or whether transport serves simply to regulate the local extracellular proline concentration. These studies will take advantage of findings that the tetrapeptide gly- gly-phe-leu potently and selectively inhibits high affinity proline transport and that the lateral and medial divisions of the hippocampal perforant path differ markedly in their ability to take up proline. A final study will investigate the mechanism by which proline depresses glutamate release. This effect is observed with concentrations of proline that are present in the cerebrospinal fluid of persons having hyperprolinemia type II, but not with normal proline concentrations. Findings from the proposed studies will elucidate a novel regulation of glutamate transmission that may be an attractive target for drug development. They may also prove relevant to synaptic mechanisms of memory and learning.