The Effects of Fentanyl on the Contractile Response of Ovalbumin-Sensitized Rat Trachea

It is not clear whether fentanyl affects a hyperresponsive airway. We examined the effects of fentanyl on the contractile response of ovalbumin (OA)-sensitized rat tracheas.Rats were sensitized with a single intraperitoneal injection of 10 mug of OA mixed with adjuvant. Fourteen days later, the trachea was cut into 3-mm-wide rings. The OA-induced tension was measured, and the effects of fentanyl were studied in the presence of naloxone. Second, the role of cholinergic nerves and serotonin in the contraction and the effects of fentanyl were examined using tetrodotoxin and ketanserin. Third, lungs of sensitized rats were ventilated, and respiratory system resistance was calculated before and after the administration of OA in the presence of fentanyl.Fentanyl dose-dependently attenuated the OA-induced contraction, and naloxone partly reversed it. Both tetrodotoxin and ketanserin attenuated the contraction. Fentanyl had no further effect on the contraction in the presence of tetrodotoxin, whereas the contraction was nearly abolished by fentanyl in the presence of ketanserin. OA increased respiratory system resistance in sensitized rats, and this effect was attenuated by fentanyl.Fentanyl attenuates the airway hyperresponsiveness of sensitized rat trachea through the inhibition of cholinergic nerves on the smooth muscle.