Contribution of vagal afferents to breathing pattern in rats with lung fibrosis

Abstract

In anesthestized male Wistar rats with bleomycin-induced lung fibrosis we examined the influence of lung vagal non-myelinated and myelinated afferents in setting breathing pattern. Fourteen days after intratracheal instillation of bleomycin, lung compliance, total lung capacity (TLC) and inspiratory capacity were reduced while functional residual capacity and residual volume were increased. Baseline tidal volume (V t) was decreased and frequency (f r) increased in the bleomycin treated rats compared with controls. Selective vagal C-fiber blockade did not affect f r or V t in any group. Vagotomy resulted in an increase in V t and decrease in f r in both groups with the percent increase in V t/TLC and decrease in f r being significantly greater in the bleomycin rats compared with controls. Vagotomy also attenuated the significantly elevated P CO 2 in the bleomycin treated rats suggesting that bleomycin-induced alterations in breathing pattern contribute to blood gas abnormalities. We conclude that vagal myelinated afferents contribute to the rapid shallow breathing in bleomycin treated rats.