NEUROBIOLOGY OF ENDOMORPHINS IN SPINAL DORSAL HORN

脊髓中的明胶质（SG）神经元是初级传入事件终止的主要部位，许多初级传入事件支配伤害感受器。内源性阿片类药物或合成化合物被认为产生抗伤害感受器。内源性阿片或合成化合物被认为是通过与SG神经元上的阿片受体亚型相互作用来产生抗痛觉的。最近分离的两个四肽内啡肽（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啡肽样免疫反应性（Endo-LI）亚型。初步结果表明，内啡肽样免疫反应性（Endo-LI）定位于大鼠背角浅层神经纤维的密集网络。因此，大鼠背角提供了一个独特的机会来验证内源性释放Endo-1/Endo-2的假设，并可能调节SG神经元的活动。会议将讨论两个主要问题。首先，通过放射性微探针技术评估麻醉大鼠体内或离体脊髓内源性或内源性内源性内啡肽的释放。通过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啡肽的释放是否发生改变。其次，利用全细胞贴片记录技术研究Endo对大鼠脊髓横切片单个SG神经元的细胞作用及其信号转导机制。我们的初步结果表明，远藤通过超极化膜和/或减弱突触传递来抑制SG神经元的活性。在这一建议中，Endo的突触前和突触后的作用将被电生理学和药理学评估。我们将研究可能导致Endo超极化作用的K+通道亚型。同样，Ca2+和/或K+通道的亚型(s)偶联到突触前阿片受体，可能介导Endo的突触抑制作用将被评估。该项目的长期目标是提高我们目前对这类新型阿片肽在背角神经元上的作用部位和机制的理解，以开发一类具有治疗潜力的新型阿片化合物。

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.