H. Aizawa et al., N-omega-nitro-L-arginine methyl ester increases airway responsiveness to serotonin but not to acetylcholine in cats in vivo, RESPIRATION, 68(3), 2001, pp. 286-291
Background: We previously reported that N-omega-nitro-L-arginine methyl est
er (L-NAME) enhances airway responsiveness to inhaled serotonin in cats tre
ated with atropine and propranolol. Objective: To further elucidate the rol
e of nitric oxide (NO) in airway responsiveness, we investigated whether L-
NAME induces airway hyperresponsiveness to serotonin and acetylcholine (ACh
) in animals with intact innervation. Methods: Cats were anesthetized with
pentobarbital sodium (50 mg/kg, i.p.), and mechanically ventilated. To asse
ss airway responsiveness, we measured increase in total pulmonary resistanc
e (Rr) produced by delivering serotonin or ACh aerosol to the airway, and d
etermined PC200 (the concentration which caused a 200% increase in R-L). Re
sults: The following results were obtained: (1) Airway responsiveness to se
rotonin was significantly enhanced by the administration of L-NAME (100 mg/
kg) in animals treated with atropine and propranolol. (2) Airway responsive
ness to serotonin was also significantly enhanced by L-NAME in animals with
intact innervation. (3) In contrast, airway responsiveness to ACh was not
changed by the addition of L-NAME in cats with intact innervation. Conclusi
on: These results suggest that NO modulates nonspecific airway responsivene
ss in animals with intact innervation, presumably by a reflex mechanism. Co
pyright (C) 2001 S. Karger AG, Basel.