Afferent vagal pathways mediating respiratory reflexes evoked by ROS in the lungs of anesthetized rats.
We investigated the afferent vagal pathways mediating respiratory reflexes evoked by reactive oxygen species (ROS) in the lungs of anesthetized rats. Spontaneous inhalation of 0.2% aerosolized H(2)O(2) acutely evoked initial bradypnea followed by delayed tachypnea, which was frequently mixed with delayed augmented inspiration. The initial response was abolished after perivagal capsaicin treatment (PCT), but was prolonged during vagal cooling (VC) to 7 degrees C; PCT and VC are known to differentially block the conduction of unmyelinated C and myelinated fibers, respectively. The delayed responses were eliminated during VC but emerged earlier after PCT. Vagotomy, catalase (an antioxidant for H(2)O(2)), dimethylthiourea (an antioxidant for. OH), or deferoxamine (an antioxidant for. OH) largely or totally suppressed these reflexive responses, whereas sham nerve treatment, heat-inactivated catalase, saline vehicle, or iron-saturated deferoxamine failed to do so. These results suggest that 1) the H(2)O(2)-evoked initial and delayed airway reflexes are antagonistic and may result from stimulation of lung C fibers and rapidly adapting receptors, respectively, and 2) the reflex effects of H(2)O(2) are, in part, due to the action of. OH on these afferents.
Ruan
Ting
T
Institute of Physiology, School of Medicine, National Yang-Ming University, and Department of Otolaryngology, Taipei Veterans General Hospital, Taipei 112, Taiwan.
Ho
Ching-Yin
CY
Kou
Yu Ru
YR
D000336:Aerosols; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002211:Capsaicin / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006861:Hydrogen Peroxide / Q000494:pharmacology; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000294:innervation; D008297:Male; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D016877:Oxidants / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D015656:Respiratory Mechanics / Q000187:drug effects; D013268:Stimulation, Chemical; D013990:Tidal Volume; D014630:Vagus Nerve / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
D000336:Aerosols; D000975:Antioxidants; D016877:Oxidants; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D002374:Catalase; D002211:Capsaicin