Role of Glutamate Metabotropic Receptors in Synaptic Function in the Spinal Cord

谷氨酸代谢型受体在脊髓突触功能中的作用

• 批准号: 9604654
• 负责人: Mirjana Randic
• 金额: $ 25.5万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-03-01 至 2000-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9604654&HistoricalAwards=false
• 关键词: Role; Glutamate; Metabotropic; Receptors; Synaptic

9604654 Randic The perception of pain requires excitatory synaptic transmission from primary afferent sensory fibers to secondary projection neurons in the dorsal horn (DH) region of the spinal cord. It is now well established that the primary afferent fibers use glutamate, or related amino acid, to mediate this initial excitatory step in the pain pathway. Glutamate produces its effects through two broad categories of receptors called ionotropic and metabotropic. The activation of ionotropic glutamate receptors is essential for fast excitatory transmission in the brain and spinal cord. Multiple metabotropic glutamate receptors (mGluRs) are expressed in neurons of the spinal cord dorsal horn (DH), the site of processing of sensory signals, but their roles in synaptic function, and contribution to the spinal somatosensory transmission, including nociception, have yet to be elucidated. Until recently, progress in identifying the physiological and pathophysiological roles of mGluRs has been hindered by the lack of selective agonists and antagonists. The recent development of ligands that bind specifically to these receptors has provided a means of characterizing the important roles they may play in tuning of fast synaptic transmission, including the induction of long-term changes in synaptic efficacy. Three major objectives of the proposed study are: 1. To pharmacologically identify mGluR subtype(s) involved in modulation of primary afferent neurotransmission and synaptic plasticity in the spinal cord dorsal horn (laminae I-II). 2. To examine whether activation of the Group I mGluRs (mGluR1 and/or mGluR5) mobilizes Ca2+ from internal stores in LI-II neurons. 3. To study characteristics of Ca2+-induced Ca2+ release mechanism in the generation of Ca2+ signals in LI-II neurons. A combination of fura-2 imaging, extracellular, intracellular (sharp microelectrodes) and whole-cell and perforated-patch recordings, and pharmacological techniques, will be employed to study the effects of selective mGluR agonists and antagonists on excitatory synaptic responses and mobilization of Ca2+ from internal stores in the in vitro preparations of acutely isolated DH neurons (LI-II), and also in the LI-II neurons within rat spinal cord slices. LI-II cells in the spinal slices will be visualized using infra-red videomicroscopy and intracellular labeling with biocytin and rhodamine. Delineating the physiological roles of individual subtypes of the mGluR in the spinal DH, and cellular and molecular mechanisms underlying their actions, is an important step toward understanding of implications of glutamate-mediated transmission in the spinal cord DH synaptic function, but in particular for synaptic plasticity. Finally, this study may contribute to our understanding of pathophysiological processes in the spinal cord, especially pain, and thereby may lead to the development of rational therapies.

疼痛的感知需要从初级传入感觉纤维到脊髓背角（DH）区的次级投射神经元的兴奋性突触传递。现在已经确定，初级传入纤维使用谷氨酸或相关氨基酸来介导疼痛通路中的这一初始兴奋步骤。谷氨酸通过两大类受体产生作用，即嗜离子性受体和促代谢受体。嗜离子性谷氨酸受体的激活对于大脑和脊髓的快速兴奋传递是必不可少的。多种代谢性谷氨酸受体（mGluRs）在处理感觉信号的脊髓背角（DH）神经元中表达，但它们在突触功能中的作用以及对脊髓体感觉传递（包括伤害感觉）的贡献尚未阐明。直到最近，由于缺乏选择性激动剂和拮抗剂，确定mGluRs的生理和病理生理作用的进展一直受到阻碍。最近发展的与这些受体特异性结合的配体提供了一种方法来表征它们在调节快速突触传递中可能发挥的重要作用，包括诱导突触功效的长期变化。拟建研究的三个主要目标是：1。药理学鉴定参与脊髓背角（I-II层）初级传入神经传递和突触可塑性调节的mGluR亚型。2. 研究I组mGluRs （mGluR1和/或mGluR5）的激活是否能从LI-II神经元的内部储存中动员Ca2+。3. 研究LI-II神经元Ca2+信号产生过程中Ca2+诱导Ca2+释放机制的特点。结合fura-2成像、细胞外、细胞内（尖锐微电极）、全细胞和穿孔贴片记录以及药理学技术，将研究选择性mGluR激动剂和拮抗剂对急性分离DH神经元（LI-II）体外制备和大鼠脊髓切片内LI-II神经元中兴奋性突触反应和从内部储存中动员Ca2+的影响。脊髓切片中的LI-II细胞将使用红外视频显微镜和生物细胞素和罗丹明的细胞内标记进行可视化。描述mGluR的个体亚型在脊髓DH中的生理作用，及其作用背后的细胞和分子机制，是理解谷氨酸介导的脊髓DH突触功能传递的重要一步，尤其是突触可塑性。最后，这项研究可能有助于我们理解脊髓的病理生理过程，特别是疼痛，从而可能导致合理治疗的发展。