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

小行星9604654 疼痛的感知需要从初级传入感觉纤维到脊髓背角（DH）区域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初始兴奋步骤。 谷氨酸通过两大类称为离子型和代谢型的受体产生作用。 离子型谷氨酸受体的激活对于大脑和脊髓中的快速兴奋性传递至关重要。 多种代谢型谷氨酸受体（mGluRs）在脊髓背角（DH）神经元中表达，背角是感觉信号的处理部位，但它们在突触功能中的作用以及对脊髓体感传递（包括伤害感受）的贡献尚未阐明。 直到最近，在确定mGluRs的生理和病理生理作用的进展一直受到阻碍的缺乏选择性激动剂和拮抗剂。 最近开发的配体，特异性结合这些受体提供了一种手段，表征的重要作用，他们可能发挥快速突触传递的调谐，包括诱导突触功效的长期变化。 本研究的三个主要目的是：1.初步鉴定参与脊髓背角（板层I-II）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（mGluR 1和/或mGluR 5）的激活是否从LI-II神经元的内部储存中动员Ca 2+。 3.目的：研究钙离子介导的钙释放机制在LI-Ⅱ神经元钙信号产生中的特点。 Fura-2成像的组合，细胞外，细胞内（尖锐微电极）和全细胞和穿孔贴片记录，以及药理学技术，将被用来研究选择性mGluR激动剂和拮抗剂对兴奋性突触反应的影响，以及在急性分离的DH神经元（LI-II）的体外制剂中从内部储存中动员Ca 2+，以及在大鼠脊髓切片内的LI-II神经元中。 将使用红外视频显微镜和用生物胞素和罗丹明进行细胞内标记来可视化脊髓切片中的LI-II细胞。 阐明mGluR在脊髓DH中的各个亚型的生理作用，以及它们作用的细胞和分子机制，是理解脊髓DH突触功能中谷氨酸介导的传递的重要一步，特别是突触可塑性。 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。

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.