Mechanisms and Consequences of Locus Coeruleus Activation

描述（由申请人提供）：神经性疼痛反映了周围、脊髓和脊髓上结构的无数变化。有趣的是，尽管发生了一系列令人困惑的变化，但许多批准的神经性疼痛治疗方法仍会增加、增强或模拟球脊髓抑制，包括吗啡、去甲肾上腺素（NA）再摄取抑制剂和可乐定。尽管临床研究表明神经性疼痛患者存在下降抑制的基线缺陷，但我们认为该通路的激活是几种有效且已获批准的治疗方法所涉及的关键机制。加巴喷丁（GBP）常用于神经性疼痛的治疗，但其镇痛机制尚不完全清楚。我们最近证明了GBP通过谷氨酸能信号激活蓝斑（LC）神经元，并且GBP对周围神经损伤大鼠的抗超敏作用依赖于这种激活和随后的脊髓NA释放。本提案的目标是确定GBP调节谷氨酸释放以激活LC的机制，并确定GBP对LC神经元输入的机制是否适用于整体或特定的涉及镇痛和不良反应的亚群，如嗜睡，注意力减少和记忆保留。首先，我们将通过突触体和微透析研究GBP调节GABA调节LC突触前谷氨酸释放的机制。其次，我们将通过培养星形胶质细胞和微透析来研究GBP调节LC中独特的星形胶质细胞-神经元相互作用以增加细胞外谷氨酸的机制。最后，我们将在LC中给予GBP，并通过微透析比较脊髓、前额叶皮层、下丘脑腹外侧视前区和海马背侧NA的释放，以测试GBP诱导的LC激活是一种全局现象还是选择性地控制疼痛、注意力、唤醒和记忆的投射。本实验不仅为理解GBP的镇痛机制提供了重要信息，而且为神经性疼痛的治疗提供了新的假设。

DESCRIPTION (provided by applicant): Neuropathic pain reflects a myriad of changes in the periphery, spinal cord, and supra-spinal structures. Interestingly, despite this baffling array of changes, many approved treatments for neuropathic pain recruit, augment, or mimic bulbospinal inhibition including morphine, noradrenaline (NA) re-uptake inhibitors, and clonidine. Although clinical studies suggest a baseline deficit of descending inhibition in patients with neuropathic pain, we believe that activation of this pathway is a key mechanism engaged by several effective and approved treatments. Gabapentin (GBP) is commonly used for treatment of neuropathic pain but its mechanisms for analgesia are not entirely known. We recently demonstrated GBP activates locus coeruleus (LC) neurons via glutamatergic signaling and that the anti-hypersensitivity effects of GBP in rats with peripheral nerve injury relies on this activation and subsequent spinal NA release. The goals of this proposal are to identify the mechanisms by which GBP regulates glutamate release to activate the LC and also to determine whether the mechanisms of GBP on input to LC neurons apply globally or specifically to subsets involved in analgesia and adverse effects such as somnolence, reduction of attention, and memory retention. Initially, we will examine mechanisms by which GBP modulates GABA regulation of pre-synaptic glutamate release in the LC using synaptosomes and microdialysis. Secondly, we will examine mechanisms by which GBP modulates the unique astroglial-neuronal interaction in the LC to increase extracellular glutamate, using cultured astrocytes and microdialysis. Lastly, we will administrate GBP in the LC and compare NA release in the spinal cord, prefrontal cortex, ventro-lateral preoptic area of the hypothalamus, and the dorsal hippocampus by using microdialysis to test whether GBP-induced activation in the LC is a global phenomenon or selective to projections controlling pain, attention, arousal and memory. The proposed experiments will not only provide important information for understanding analgesic mechanisms of GBP but also lead to novel hypothesis regarding the treatment of neuropathic pain. PUBLIC HEALTH RELEVANCE: Gabapentin is widely used to treat chronic pain, but how it works is not well understood. In this proposal, we will study how gabapentin stimulates a natural pain-relief mechanism to reduce pain but also to cause side effects.