| Summary: | 博士 === 國防醫學院 === 醫學科學研究所 === 95 === In cold environments, nasal resistance increased, although the mechanism is not well understood. This is because multiple mechanisms are involved in nasal obstruction in vivo, including mucosal swelling, which is often a result of increases in mucosal blood content, cellular infiltration, tissue edema, nasal valve mechanism, and neural pathways. As a result, it is feasible to investigate this underlying mechanism in an in vitro experimental study.
Results showed that the tension of isolated human nasal mucosa was temperature-dependent, with tension decreasing to 48.6% at 10°C in comparison with 100 % at 37°C. Similar results were observed by methoxamine-induced tension. Thus, low temperature induced rapid and reproducible relaxation in isolated human nasal mucosa. Because decellularized nasal mucosa also exhibited the similar cooling-induced relaxation response, suggesting this response is caused by structural factor instead of vascular smooth muscle itself. The elastin may play an important role in such cooling-induced relaxation. In contrast, moderate cooling (24°C) enhanced the vascular responsiveness of isolated human nasal mucosa. Cooling not only prolonged the electrical field stimulation-induced but also enhanced norepinephrine (3x10-6 to 1x10-4 M)-induced contraction of isolated human nasal mucosa. Besides, in comparison with the results at room temperature (24°C), there was a decreased blood flow measured by laser-Doppler flowmeter after exposure to cold (4°C) ambient air temperature.
I concluded that low temperature decreased the tension of isolated human nasal mucosa and moderate cooling (24°C) enhanced the vascular responsiveness of isolated nasal mocosa. This study suggests that, (1), the increased nasal resistance in cold environment results from increased in nasal mucosa volume which could be by extracellular matrix expansion. And (2), despite the function of air-conditioning of nasal cavity in cold environment, the vascular response of nasal mucosa to cooling is similar to that of superficial blood vessel.
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