Mechanisms and Consequences of Locus Coeruleus Activation

描述(申请人提供)：神经性疼痛反映了周围、脊髓和脊柱上结构的无数变化。有趣的是，尽管有这样一系列令人费解的变化，许多被批准的神经病理性疼痛的治疗方法包括吗啡、去甲肾上腺素(NA)再摄取抑制剂和可乐定，它们重新招募、增强或模拟了球脊髓抑制。虽然临床研究表明神经病理性疼痛患者存在下行抑制的基线缺陷，但我们认为这一通路的激活是几种有效和经批准的治疗方法的关键机制。加巴喷丁(GBP)通常用于治疗神经病理性疼痛，但其镇痛机制尚不完全清楚。我们最近证实，GBP通过谷氨酸能信号激活蓝斑(LC)神经元，GBP在周围神经损伤大鼠中的抗过敏作用依赖于这种激活和随后的脊髓NA释放。本研究的目的是确定GBP调节谷氨酸释放以激活LC的机制，并确定GBP对LC神经元的输入机制是否适用于涉及镇痛和不良反应(如嗜睡、注意力减退和记忆保持)的亚群。首先，我们将使用突触小体和微透析来研究GBP调节GABA调节LC中突触前谷氨酸释放的机制。其次，我们将利用培养的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，并通过微透析法比较脊髓、前额叶皮质、下丘脑腹外侧视前区和背侧海马中NA的释放，以测试LC中GBP诱导的激活是一种全局现象还是对控制疼痛、注意力、觉醒和记忆的投射具有选择性。这些实验不仅将为理解GBP的止痛机制提供重要信息，而且还将为神经病理性疼痛的治疗提供新的假说。

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.