Functional role and therapeutic potential of the glycine transporter GlyT1 in chronic pain

痛觉的主要功能是保护机体免受伤害性刺激的伤害。伤害感受系统内的适应不良可塑性可导致异常性疼痛和/或痛觉过敏。在这些条件下，疼痛失去了它的保护作用，并被认为是一个自主的疾病本身。尽管受影响的患者遭受了广泛的痛苦，并且数十年来进行了大量的研究，但导致这些慢性疼痛状况的神经元机制仍然知之甚少，治疗方案仍然不令人满意。在最近的方法中，恢复脊髓背角内的抑制性神经传递已成为开发慢性疼痛病症的新治疗选择的主要目标。然而，GABA能神经传递的增强已被证明是困难的，部分原因是在较高的大脑区域中GABAA受体的高丰度导致不利的副作用。由于甘氨酸能神经传递主要限于中枢神经系统的尾部，因此预计不会出现类似的中枢副作用。因此，甘氨酸能系统似乎是一个有前途的新目标的治疗方法对慢性疼痛。我们以前已经表明，药理学减少甘氨酸转运蛋白1（GlyT 1）的甘氨酸摄取活性有效地减少了促进疼痛反应的动物模型中的神经性疼痛以及炎性疼痛。在这个项目中，我们的目标是阐明如何抑制GlyT 1改善慢性疼痛的分子生物学和组织学以及神经生理学的方法相结合的跨学科项目。详细地说，我们计划利用一个小鼠系，携带一个修改的GlyT 1等位基因允许Cre重组酶介导的GlyT 1表达失活。通过Cre重组酶在该小鼠系的小鼠中的稳定转基因或病毒诱导表达，我们计划获得细胞类型和/或区域特异性GlyT 1缺陷。在这些小鼠中，我们计划首先确定甘氨酸依赖的抑制性和兴奋性神经传递的背角神经元的电生理方法GlyT 1缺乏的后果。随后，我们计划在这些小鼠中诱导神经性或炎性疼痛条件，并通过生物化学，组织学和电生理学方法确定伴随疼痛慢性化的神经可塑性变化。 与野生型动物的比较将揭示相应GlyT 1群体对GlyT 1活性物质在慢性疼痛背景下的作用的影响。总之，该项目将提供有关在生理条件下和慢性疼痛影响下脊髓内GlyT 1细胞类型特异性功能的新信息。这将为作用于GlyT 1的物质影响慢性疼痛的机制提供新的见解。

The main function of pain perception is to protect organisms from damage caused by noxious stimuli. Maladaptive plasticity within the nociceptive system can result in allodynia and/or hyperalgesia. Under these conditions pain loses its protective role, and is considered as anautonomous disease in itself. Despite extensive suffering of affected patients and intense research over decades, the neuronal mechanisms leading to these chronic pain conditions pain are still only poorly understood and treatment options remain rather unsatisfying. In recent approaches, the restoration of inhibitory neurotransmission within the dorsal horn of spinal cord has been a major aim for the development of new treatment options for chronic pain conditions.The enhancement of GABAergic neurotransmission, however, has proven difficult in part due to the high abundance of GABAA receptors in higher brain regions that cause unfavourable side effects. Since glycinergic neurotransmission is largely restricted to caudal parts of the central nervous system, similar central side effects are not to be expected. Therefore, the glycinergic system seems to be a promising novel target for therapeutic approaches against chronic pain. We have shown previously that pharmacological reduction of the glycine transporter 1 (GlyT1) glycine uptake activity efficiently reduces the facilitated pain response in animal models of neuropathic as well as inflammatory pain. In this project we aim to elucidate the mechanisms how inhibition of GlyT1 ameliorates chronic pain by an interdisciplinary project combining molecular biological and histological as well as neurophysiological approaches.In detail, we plan to make use of a mouse line that carries a modified GlyT1 allele allowing the Cre recombinase mediated inactivation of GlyT1 expression. By stable transgenic or viral induced expression of Cre recombinase in mice of this mouse line we plan to obtain a cell type and/or regions specific GlyT1 deficiency. In these mice, we plan first to determine the consequences of GlyT1 deficiency on glycine dependent inhibitory and excitatory neurotransmission by an electrophysiological approach in dorsal horn neurons. Subsequently we plan to induce neuropathic or inflammatory pain conditions in these mice and determine the neuroplastic changes that accompany the chronification of pain, by biochemical, histological and electrophysiological methods. Comparison to wild-type animals will reveal the inpact of the respective GlyT1 population on the effects of Glyt1 active substances in the context of chonic pain. Taken together this project will provide new information on the cell type specific functions of GlyT1 within the spinal cord both under physiological conditions and under the influence of chronic pain. This will provide new insight on the mechanism by which substances acting on GlyT1 influence chronic pain.