Stimulation of vagal pulmonary C fibers by inhaled wood smoke in rats

Lai, C. J., and Y. R. Kou. Stimulation of vagalpulmonary C fibers by inhaled wood smoke in rats. J. Appl. Physiol. 84(1): 30-36, 1998.This studyinvestigated the stimulation of vagal pulmonary C fibers (PCs) by woodsmoke. We recorded impulses from PCs in 58 anesthetized, open-chest,and artificially ventilated rats and delivered 6 ml of wood smoke intothe lungs. Within 1 or 2 s after the smoke delivery, an intense andnonphasic burst of discharge [ = +7.4 ± 0.7 (SE)impulses/s, n = 68] was evoked in 60 of the 68 PCs studied and lasted for 4-8 s. This immediate stimulation was usually followed by a delayed and more sustained increase in C-fiber activity ( = +2.0 ± 0.4 impulses/s). The overall stimulation was not influenced by removal of smoke particulates (n = 15) or by pretreatment withvehicle (n = 8) for dimethylthiourea (DMTU; a hydroxyl radical scavenger) or indomethacin (Indo; a cyclooxygenase inhibitor). The immediate-phase stimulation was notaffected by pretreatment with Indo (n = 8) but was largely attenuated by pretreatment with DMTU(n = 12) or by a combined treatmentwith DMTU and Indo (DMTU+Indo; n = 8).Conversely, the delayed-phase stimulation was partially suppressedeither by DMTU or by Indo but was totally abolished by DMTU+Indo. Theseresults suggest that 1) thestimulation of PCs is linked to the gas phase of wood smoke and2) hydroxyl radical, but notcyclooxygenase products, is involved in the immediate-phasestimulation, whereas both metabolites are responsible for evoking thedelayed-phase stimulation.