| Summary: | 碩士 === 國立中山大學 === 生物科學系研究所 === 92 === Vagal and spinal sensory innervation is responsible for the regulation of neurogenic inflammation in the airways. Neurogenic inflammation is the result of the activation of sensory nerve endings by stimulant and induced through axon reflex to release neuropeptides from sensory nerve endings. These neuropitides are tachykinins, including substance P, neurokinin A and neuronkinin B. Tachykinin-1 (NK-1) receptors are mainly involved in neurogenic inflammation in the airway. It is found that 6-hydroxydopamine (6-OHDA) acts as a stimulant of sensory neurons that produces inflammation in the rat trachea. The magnitude of plasma leakage was expressed by the area density (%) of India ink-labeled blood vessels in tissue whole mounts. The present study found that area density of India ink-labeled blood vessel were 36.5%, 29.5%, 27.7%, 28.2%, 19.2%, 15.5% in the rat larynx, trachea, left bronchus, right bronchus, upper esophagus and distal esophagus after i.v. injection of 6-OHDA (100 mg /Kg), respectively. 6-OHDA could stimulate sensory neurons by free radicals that produced by non-enzymatic oxidation. NK-1 receptor antagonist can inhibit plasma leakage in airways. This study also tested the effect of a free radical scavenger. Rats are pretreated with a full dose (2.25 g/kg, i.v.) or lower doses of dimethylthiourea (DMTU) for a period of 15 min. We found that pretreatment with a full dose of DMTU could inhibit inflammatory plasma leakage induced by 6-OHDA, that was 4.8%, 1.6%, 1.1%, 2.4%, 0.4% and 1.0% in the rat larynx, trachea, left bronchus, right bronchus, upper esophagus and distal esophagus, respectively. It is suggested hydroxyl radicals mediated the inflammatory response in the respiratory tract and esophagus. DMTU dose-dependently decreased 6-OHDA-induced plasma leakage in the rat respiratory tract and esophagus. One sixth dose was effective in inhibition in esophagus. 6-OHDA-induced inflammation in the left and right bronchus could be reduced with 2/3 dose of DMTU. A full dose of DMTU (2.25g/Kg) was needed to inhibit inflammation in the larynx and trachea. It is concluded that sensitivity to 6-OHDA was different in the different part of lower airways and esophagus.
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