SPINAL NITRIC OXIDE IN CHRONIC INFLAMMATORY PAIN

未经治疗的慢性疼痛会导致中枢神经系统(CNS)内神经回路的重组、中枢敏感化和疼痛加剧。慢性疼痛患者往往情绪低落，发病率较高。在慢性炎症动物模型中，爪部和关节炎症同时伴有热痛敏和机械性痛敏，以及血浆和关节滑膜组织中一氧化氮(NO)的产生增加。一氧化氮是由精氨酸合成的一氧化氮合酶(NOS)，至少存在三种亚型，即构成内皮(CeNOS)、神经元(CnNOS)和诱导型(INOS)。虽然炎症中NO增加的一个主要来源可能是iNOS的活性是参与免疫反应的外周细胞，但在脊髓也发现了NOS活性的增加，脊髓是疼痛处理的第一个中继站。脊髓iNOS和cnNOS在炎性疼痛中的相对活性及其在痛觉过敏和炎症中的作用尚不清楚。拟议的研究旨在验证脊髓cnNOS活性与慢性炎症性疼痛中观察到的炎症和痛敏有关的假设。通过给大鼠注射肽聚糖/多糖(PG/PS)或完全弗氏S佐剂(CFA)来诱导慢性炎症，这些治疗方法会产生肢体的慢性炎症。具体目的是：(1)选择性抑制脊髓cnNOS活性，或直接向脊髓内注射反义寡核苷酸(ODN)，检测外周炎症反应、热和机械伤害性反应。免疫细胞化学方法检测炎症发生和维持过程中不同时间点脊髓cnNOS蛋白在脊髓切片和背根神经节的表达。脊髓匀浆的总一氧化氮合酶活性也将通过测量精氨酸到瓜氨酸的转化来确定。这些结果将与脊髓注射错义寡核苷酸或赋形剂获得的结果进行比较。(2)建立NO敏感微电极实时原位测定麻醉大鼠脊髓NO释放量的方法。这项技术将被用来测量对炎症和非炎症的后爪进行有害机械刺激后脊髓NO的释放。CnNOS抑制对这种释放的影响将被测量。这些研究的结果将提供有关脊髓NO在启动、发育和维持或外周慢性炎症和痛觉过敏中的作用的信息。这些信息可以用来开发治疗慢性炎症性疼痛或其他类型的慢性疼痛的新药。

Untreated chronic pain leads to reorganization of neuronal circuits within the central nervous system (CNS), central sensitization, and enhanced pain. Chronic pain patients are often depressed, with higher morbidity probability. In animal models of chronic inflammation, paw and joint inflammation is accompanied by both thermal and mechanical hyperalgesia as well as increased nitric oxide (NO) production in plasma and joint synovial tissue. Nitric oxide is synthesized from arginine by NO synthase (NOS) which is found in at least three isoforms, constitutive endothelial (ceNOS) and neuronal (cnNOS) and inducible (iNOS). Although a major source of increased NO in inflammation is likely due to activity of iNOS is peripheral cells involved in the immune response, increased NOS activity is also found in spinal cord, the first relay site for pain processing. The relative activities of spinal iNOS and cnNOS in inflammatory pain and their contributions to hyperalgesia and inflammation are not known. The proposed studies are designed to test the hypothesis that spinal cnNOS activity contributes to both the inflammation and the hyperalgesia observed in chronic inflammatory pain. Chronic inflammation will be induced by administration of peptidoglycan/polysaccharide (PG/PS) or complete Freund s adjuvant (CFA) into rats, treatments that produce chronic inflammation of the limbs. Specific aims are to (1) selectively inhibit activity of spinal cnNOS with selective inhibitors or antisense oligodeoxynucleotide (ODN) administered directly into the spinal cord and measuring peripheral inflammation and thermal and mechanical nociception. Expression of spinal cnNOS protein in spinal cord slices and dorsal root ganglia will be measured by immunocytochemistry at various time points during development and maintenance of inflammation. Total NOS activity is spinal cord homogenates will also be determined by measuring conversion of arginine to citrulline. These results will be compared to those obtained with spinal injection of missense ODN or vehicle. (2) develop a technique using a NO-sensitive microelectrode to measure real time in situ release of NO in the spinal cord of anesthetized rats. This technique will be used to measure spinal NO release following noxious mechanical stimulation of both inflamed and non-inflamed hindpaws. Effects of cnNOS inhibition on this release will be measured. Results of these studies will provide information about the role of spinal NO in initiation, development and maintenance or peripheral chronic inflammation and hyperalgesia. This information can be used to develop new drugs to treat chronic inflammatory pain or other types of chronic pain.