title: Enhanced lung C-fiber responsiveness in sensitized adult guinea pigs exposed to chronic tobacco smoke.
abstract: Tobacco smoke (TS) exposure induces bronchoconstriction and increases airway secretions and plasma extravasation in certain sensitive individuals, particularly those with asthma. C-fiber activation also induces these effects. Although the mechanism by which chronic TS exposure induces airway dysfunction is not well understood, TS exposure may enhance C-fiber responsiveness. To investigate the effect of chronic TS exposure on C-fiber responsiveness to capsaicin and bradykinin, especially in atopic individuals, we exposed ovalbumin (OA)-sensitized guinea pigs to TS (5 mg/l air, 30 min/day for 7 days/wk) or to compressed air. Nonsensitized guinea pigs were also exposed to either compressed air or TS. Beginning after 120 days of exposure, C fibers and rapidly adapting receptors (RARs) were challenged with capsaicin and bradykinin. TS exposure enhanced sensory receptor and airway responsiveness to both intravenous capsaicin and bradykinin challenge. C-fiber, RAR, and airway responsiveness to capsaicin challenge was greatest in OA-sensitized guinea pigs exposed to TS. OA alone induced capsaicin hyperresponsiveness at 5 microg. Airway responsiveness to bradykinin was also greatest in OA-sensitized guinea pigs exposed to TS. OA alone enhanced C-fiber responsiveness to bradykinin at 5 and 10 microg. C-fiber activation by either agonist appeared direct, whereas RAR activation appeared indirect. Therefore, a mechanism of airway hyperirritability induced by the combination of OA sensitization and chronic TS exposure may include hyperirritability of lung C fibers.
authors.affiliation: Department of Biomedical Sciences, School of Medicine, Creighton University, Omaha, Nebraska 68178, USA. dbergren@creighton.edu
authors.forename: D R
authors.initials: DR
authors.lastname: Bergren
mesh_terms: D000280:Administration, Inhalation; D000403:Airway Resistance / Q000187:drug effects; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002211:Capsaicin / Q000008:administration & dosage / Q000494:pharmacology; D002452:Cell Count; D006168:Guinea Pigs; D006439:Hemodynamics / Q000187:drug effects; D007275:Injections, Intravenous; D008168:Lung / Q000294:innervation* / Q000473:pathology; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D010991:Plethysmography; D012130:Respiratory Hypersensitivity / Q000503:physiopathology; D015656:Respiratory Mechanics / Q000502:physiology; D012907:Smoking / Q000473:pathology / Q000503:physiopathology*; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D002211:Capsaicin; D001920:Bradykinin