Protective and defensive airway reflexes evoked by nasal exposure to wood smoke in anesthetized rats.
We investigated the airway responses evoked by nasal wood smoke in anesthetized Sprague-Dawley rats. Wood smoke (5 ml, 1.4 ml/s) was delivered into an isolated nasal cavity while animals breathed spontaneously. In study 1, nasal wood smoke triggered either an apneic response (n = 26) or a sniff-like response (n = 16) within 1 s after smoke exposure in 42 normal rats. Both airway responses were abolished by trigeminal nerve denervation and by nasal application of a local anesthetic or a hydroxyl radical scavenger, but they were not significantly affected by removal of smoke particulates or nasal application of a saline vehicle. In study 2, nasal wood smoke only triggered a mild apneic response in two rats neonatally treated with capsaicin and had no effect on breathing in the other six; the treatment is known to chronically ablate C fibers and some Adelta fibers. In contrast, nasal wood smoke evoked an apneic response in six rats neonatally treated with the vehicle of capsaicin and elicited a sniff-like response in the other two. These results suggest that the apneic and sniff-like responses evoked by nasal wood smoke result from the stimulation of trigeminal nasal C-fiber and Adelta-fiber afferents by the gas-phase smoke and that hydroxyl radical is the triggering chemical factor.
Ho
C L
CL
Institute of Physiology, School of Medicine and Life Science, National Yang-Ming University, Taipei, Taiwan 11221, Republic of China.
Kou
Y R
YR
D000818:Animals; D001049:Apnea / Q000209:etiology / Q000503:physiopathology; D007509:Irritants / Q000633:toxicity; D008297:Male; D009296:Nasal Cavity; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000502:physiology; D012137:Respiratory System / Q000503:physiopathology*; D012906:Smoke / Q000009:adverse effects*; D014934:Wood
D007509:Irritants; D012906:Smoke