1. The Graduate Institute of Clinical Medicine and Department of Otolaryngology, College of Medicine, Taipei Medical University-Shuang Ho Hospital, Taipei, Taiwan, Republic of China
2. Department of Preventive and Community Medicine, College of Medicine, Taipei Medical University-Shuang Ho Hospital, Taipei, Taiwan, Republic of China
3. Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China
Exposure to cold causes cutaneous vasoconstriction to reduce body heat loss, while the airway warms up the inspired cold air, thus suggesting that cooling might evoke a response in tracheal smooth muscle different from that in cutaneous blood vessels. The aim of this study was to evaluate the effect of temperature on isolated rat trachea, with or without electric field stimulation (EFS). Tissue bath for isolated trachea was used. An in vitro isometric contraction of trachea from healthy male Sprague-Dawley rat (body weight: ≥ 200 g) was continuously recorded. Tension in strips of rat trachea that were untreated and treated with EFS, was continuously recorded in stepwise manner at temperatures varying from 37 °C to 7 °C or from 7 °C to 37 °C. Results indicated that descent and re-ascent of temperature produced temperature-dependent tension changes. Basal tension of the trachea decreased when temperature was reduced if EFS was not applied. EFS-induced spike contraction decreased when temperature was reduced, while basal tension increased at the same time. We concluded that low temperature induced rapid and reproducible contraction in isolated rat tracheal strip only if EFS was applied. Increasing temperature reduced basal tension and enhanced EFS-induced spike contraction of the trachea at the same time.
Keywords: Trachea, smooth muscle, low temperature, in vitro study