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

描述（由申请人提供）：糖尿病神经病变的最常见形式是感觉功能障碍伴痛觉过敏以及温度和振动感知阈值降低，这导致非常令人痛苦和衰弱的临床并发症。薄束核和孤束核（NTS）最近被证明可以调节伤害性和躯体感觉反射。我们发现Zucker糖尿病肥胖（ZDF）大鼠的机械耐受阈值和对后足的热刺激和冷刺激的撤回时间持续降低。低频电针刺激ST 36穴可改善ZDF大鼠的痛觉过敏和温度/压力超敏反应。我们已经证明，神经元型一氧化氮（NO）合酶（nNOS）的表达主要增加薄核和NTS后EA ST 36大鼠。我们的初步研究表明，ZDF大鼠薄束核内源性NO减少，EA ST 36增加了核内透析液NO的释放。EA ST 36的镇痛反应由L-精氨酸NO促进，并由薄束核中NO合成的抑制剂阻断。结果支持以下假设：1）EA ST 36诱导薄束核和孤束核内源性NO合成/释放; 2）延髓背侧的NO-cGMP-GABA系统抑制躯体感觉/伤害感受性，从而改善感觉神经病变。鉴于NO在感觉/伤害性调节中的关键重要性，主要目的是：1）检查薄束核/NTS中的NO释放是否增加并且与低频EA ST的抗伤害性/过敏反应正相关36; 2）确定神经病大鼠中的痛觉过敏和对温度/压力的超敏反应是否得到改善，并且是否与增强的cFos平行。（3）研究ZDF大鼠对EA ST 36的抗伤害/过敏反应是否被给予NO供体所改善，以及是否被薄束核和/或NTS中的NO合成抑制剂所恶化;（4）针刺对薄束核和孤束核内NO-cGMP-GABA级联反应的影响。压力、温度和疼痛阈值的生理记录将与神经药理学操作、化学测定和EA/针灸结合，以测试ZDF与瘦大鼠的假设。本研究结果将进一步阐明电针/针刺诱导的薄束核/孤束核内NO与cGMP-GABA级联反应在感觉/疼痛调制中的作用机制，并为针刺对糖尿病感觉神经病变的改善作用提供新的思路。 公共卫生相关性：这些研究将促进我们对针刺诱导的一氧化氮对背侧延髓感觉/疼痛调节的生化机制的理解，并揭示针刺通过影响脑部位一氧化氮的释放/合成来改善痛觉过敏和超敏反应的治疗作用。本研究结果将有助于探索针刺抗伤害性感受的新机制，并为建立更好的针刺疗法提供科学依据，以诱导延髓背侧一氧化氮及其合酶用于治疗感觉糖尿病神经病变和其他疼痛综合征。

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.