INHALATION OF HYDROGEN SULFIDE (H2S) AUGMENTS THE PULMONARY REFLEXES

We have previously reported that H2S exerted a sensitizing effect on pulmonary vagal C-fiber afferents in anesthetized, artificially ventilated SD rats. However, whether the sensitizing effect of H2S in turn enhances pulmonary reflexes remains unknown. In anesthetized, spontaneously breathing rats, inhalation of aerosolized sodium hydrosulfide (NaHS, a donor of H2S) caused no significant changes in the baseline breathing pattern. However, the pulmonary chemoreflexes, characterized by apnea, bradycardia and hypotension, triggered by right atrial injection of capsaicin or adenosine, were potentiated after the NaHS inhalation. This potentiating effect was eliminated by pretreatment with perineural capsaicin (a selective blockade of the conduction of vagal C-fibers) or HC-030031 (an antagonist of TRPA1 receptors), but not affected by pretreatment with perineural sham surgery or HC-030031 vehicle. Furthermore, in awake, restrained guinea pigs, the cough reflexes elicited by inhalation of aerosolized capsaicin were also potentiated after the NaHS inhalation. In conclusion, H2S enhanced pulmonary reflexes, and probably resulted from its action on pulmonary C-fibers. (MOST 103-2320-B-038-014-)