Effects of Acupuncture-Induced nNOS-NO in Dorsal Medulla on Sensory Neuropathy

描述（由申请人提供）：糖尿病神经病变最常见的形式是感觉功能障碍，伴有痛觉过敏和温度和振动感知阈值降低，这导致非常痛苦和衰弱的临床并发症。细核和孤束核（NTS）最近被证明调节伤害性反射和体感觉反射。我们发现Zucker糖尿病脂肪（ZDF）大鼠后足热冷刺激的机械耐受阈值和戒断潜伏期持续降低。低频电针（EA）刺激ST36穴位可改善ZDF大鼠痛觉过敏和对温度/压力的超敏反应。我们已经证明，大鼠EA ST36后，神经元一氧化氮（NO）合成酶（nNOS）的表达主要在细核和NTS中增加。我们的初步研究表明，EA ST36可以减少ZDF大鼠细核内的内源性NO，并促进透析液NO在细胞核中的释放。对EA ST36的镇痛反应由l -精氨酸NO促进，并被细核NO合成抑制剂阻断。结果支持以下假设：1)EA ST36诱导细核和NTS内源性NO合成/释放；2)髓质背侧NO-cGMP-GABA系统抑制体感觉/伤害感受易感性，从而改善感觉神经病变。鉴于NO在感觉/伤害性调节中的重要作用，本研究的主要目的是：1)检查细核/NTS中的NO释放是否增加，并与低频EA ST36的抗伤害性/超敏反应正相关；2)观察8次EA ST36是否改善神经性病变大鼠的痛觉过敏和温度/压力超敏反应，并与细核/ nts -丘脑通路中cFos-nNOS表达增强平行；3)研究ZDF大鼠对EA ST36的抗伤害性/超敏反应是否通过给药NO来改善，而在细核和/或NTS中使用NO合成抑制剂是否会恶化；4)确定NO-cGMP-GABA级联在细核和NTS中是否响应no介导的针刺抗伤害/超敏反应。生理记录的压力，温度和疼痛阈值将与神经药理学操作，化学分析和EA/针灸相结合，以检验ZDF与瘦大鼠的假设。这一结果将有助于我们进一步了解EA/针刺诱导的细核/NTS内cGMP-GABA级联NO对感觉/疼痛调节的机制，并为针刺对髓背nNOS-NO生成的影响提供新的见解，从而改善感觉糖尿病神经病变。

DESCRIPTION (provided by applicant): The most common forms of diabetic neuropathies are sensory dysfunctions with hyperalgesia and reduced temperature and vibration perception thresholds, which lead to very distressing and debilitating clinical complications. The gracile nucleus and nucleus tractus solitarius (NTS) were recently shown to modulate nociceptive and somatosensory reflexes. We found that the mechanical tolerance threshold and withdrawal latencies of heat and cold stimuli to the hind foot are consistently decreased in Zucker diabetic Fatty (ZDF) rats. Hyperalgesia and hypersensitivity to temperature/ pressure in ZDF rats are improved by low-frequency electroacupuncture (EA) stimulation of acupoint ST36. We have demonstrated that neuronal nitric oxide (NO) synthase (nNOS) expression is predominantly increased in the gracile nucleus and NTS following EA ST36 in rats. Our preliminary studies show that endogenous NO is decreased in the gracile nucleus in ZDF rats, and dialysate NO release in the nucleus is enhanced by EA ST36. The analgesic responses to EA ST36 are facilitated by L-arginine NO and blocked by an inhibitor of NO synthesis in the gracile nucleus. The results support the following hypotheses: 1) EA ST36 induces endogenous NO synthesis/release in the gracile nucleus and the NTS; and 2) NO-cGMP-GABA system in the dorsal medulla inhibits somatosensory/nociceptive susceptibility resulting in improvement of sensory neuropathies. In view of the critical importance of NO on sensory/nociceptive regulation, the major aims are: 1) Examine whether NO release in the gracile nucleus/NTS is increased and is positively correlated to anti-nociceptive/hypersensitive responses to low-frequency EA ST36; 2) Determine whether hyperalgesia and hypersensitivity to temperature/pressure in neuropathic rats are improved and are parallel to enhanced cFos-nNOS expressions in the gracile nucleus/NTS-thalamic pathways by 8 sessions of EA ST36; 3) Investigate whether anti-nociceptive/hypersensitive responses to EA ST36 are improved by administration of NO donors and worsened by an inhibitor of NO synthesis in the gracile nucleus and/or NTS in ZDF rats; and 4) Determine whether NO-cGMP-GABA cascade in the gracile nucleus and NTS responds to NO-mediated anti-nociceptive/hypersensitive responses to acupuncture in ZDF rats. Physiological recordings of pressure, temperature, and pain thresholds will be incorporated with neuropharmacological manipulations, chemical assays and EA/acupuncture to test the hypotheses in ZDF vs. lean rats. The results will advance our understanding of the mechanisms of EA/acupuncture- induced NO with cGMP-GABA cascade in the gracile nucleus/NTS on sensory/pain modulation, and yield new insights into effects of acupuncture on nNOS-NO generation in the dorsal medulla resulting in improvement of sensory diabetic neuropathies. PUBLIC HEALTH RELEVANCE: These studies should advance our understanding of the biochemical mechanisms of acupuncture-induced nitric oxide on sensory/pain regulation in the dorsal medulla, and reveal a therapeutic effect of acupuncture on improving hyperalgesia and hypersensitivity by affecting nitric oxide release/synthesis in the brain sites. The results should benefit public health by exploring a novel anti-nociceptive mechanism of acupuncture and by establishing a better acupuncture therapy based on scientific evidence of inducing nitric oxide and its synthase in the dorsal medulla for treatment of sensory diabetic neuropathies and other pain syndromes.