NEUROBIOLOGY OF ENDOMORPHINS IN SPINAL DORSAL HORN

脊髓背角内啡肽的神经生物学

• 批准号: 6052393
• 负责人: Nae J Dun
• 金额: $ 22.14万
• 依托单位: EAST TENNESSEE STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-12-01 至 2002-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6052393
• 关键词: C fiber; G protein; biological signal transduction; calcium channel blockers; calcium flux; dorsal horn; electrophysiology; endogenous opioid; heat stimulus; immunocytochemistry; laboratory rat; mechanical pressure; membrane potentials; naloxone; naltrexone; neuropeptide receptor; opioid receptor; organ culture; pain; pertussis toxin; potassium channel; somatic afferent nerve; substance P; tachykinin; voltage /patch clamp

Substantia gelatinosa (SG) neurons in the spinal cord are the principal site of termination of primary afferents, many of which innervate nociceptors. Endogenous opiates or synthetic compounds are thought to produce their anti-nociceptors. Endogenous opiates or synthetic compounds are thought to produce their anti-nociception by interacting with subtypes of opiate receptors on SG neurons. Two recently isolated tetrapeptides endomorphin (Endo) 1 and 2 are believed to be the endogenous ligand for the mu-subtype of opioid receptors. Preliminary results showed endomorphin-like immunoreactivity (Endo-LI) subtype of opioid receptors. Preliminary results showed that endomorphin-like immunoreactivity (Endo-LI) is localized to dense networks of nerve fibers in the superficial layers of the rat dorsal horn. Thus, the rat dorsal horn offers a unique opportunity to test the hypothesis that Endo-1/Endo-2 is released endogenously and that it may modulate the activity of SG neurons. Two major issues will be addressed. First, release of endogenous of endogenous endomorphins will be evaluated in anesthetized rats in vivo or isolated rat spinal cords in vitro by the radioactive microprobe techniques. Electrical stimulation of afferent fibers of painful stimulus to the hindpaw will be employed to evaluate whether or not endomorphin release is altered under these conditions. Second, whole-cell patch recording techniques will be used to study the cellular action and the signal transduction mechanism underlying the action of Endo on single SG neurons in rat transverse spinal cord slices. Our preliminary results show that Endo inhibits the activity of SG neurons by hyperpolarizing the membrane and/or attenuating synaptic transmission. In this proposal, the pre- and post-synaptic actions of Endo will be evaluated electrophysiologically and pharmacologically. The subtype(s) of K+ channels that may underlie the hyperpolarizing action of Endo will be examined. Similarly, the subtype(s) of Ca2+ and/or K+ channels coupled to the presynaptic opiate receptor that may mediate the synaptic depressant action of Endo will be evaluated. The long term goal of this project is to improve our current understanding of the site and mechanism of action of this new class of opioid peptides on dorsal horn neurons, with the aim toward developing a novel class of opiate compounds with therapeutic potentials.

脊髓中的胶质质 (SG) 神经元是初级传入神经终止的主要部位，其中许多神经支配伤害感受器。内源性阿片类药物或合成化合物被认为可以产生抗伤害感受器。内源性阿片类药物或合成化合物被认为是通过与 SG 神经元上的阿片类受体亚型相互作用来产生抗伤害作用。最近分离出的两种四肽内吗啡肽 (Endo) 1 和 2 被认为是阿片受体 mu 亚型的内源性配体。初步结果显示阿片受体具有内吗啡样免疫反应性（Endo-LI）亚型。初步结果表明，内吗啡样免疫反应性（Endo-LI）位于大鼠背角浅层的密集神经纤维网络中。因此，大鼠背角提供了一个独特的机会来检验 Endo-1/Endo-2 是内源性释放的，并且它可能调节 SG 神经元的活性这一假设。将解决两个主要问题。首先，通过放射性微探针技术在体内麻醉的大鼠或体外分离的大鼠脊髓中评估内源性内吗啡肽的内源性释放。将采用对后爪疼痛刺激传入纤维的电刺激来评估在这些条件下内吗啡释放是否改变。其次，全细胞贴片记录技术将用于研究 Endo 对大鼠横向脊髓切片中单个 SG 神经元作用的细胞作用和信号转导机制。 我们的初步结果表明，Endo 通过使膜超极化和/或减弱突触传递来抑制 SG 神经元的活性。在该提案中，将从电生理学和药理学角度评估 Endo 的突触前和突触后作用。将检查可能是远藤超极化作用基础的 K+ 通道亚型。类似地，将评估与可介导 Endo 突触抑制作用的突触前阿片受体偶联的 Ca2+ 和/或 K+ 通道亚型。该项目的长期目标是提高我们目前对这类新型阿片肽对背角神经元的作用位点和机制的了解，旨在开发一类具有治疗潜力的新型阿片化合物。