Effect of bronchoconstriction on the firing behavior of pulmonary stretch receptors

To study the effect of bronchoconstriction on the activity of pulmonary receptors (PSRs), acetylcholine aerosols (0.05% solution) were delivered continuously into the lungs while the afferent activity of a single PSR was recorded from a filament of the vagus nerve. The relationship between the PSR frequency (f_PSR) and the transpulmonary pressure (P_tp) was examined during both constant volume ventilation and hyperinflation. During bronchoconstriction, the peak f_PSR for the same tidal volume increased significantly (P < 0.05) compared to the control response obtained with saline aerosols. However, the f_PSR at functional residual capacity decreased in the receptors above the carina but increased in those below. Bronchoconstriction induced a hysteresis in the dynamic P_tp-f_PSR relationship during hyperinflation in 11 out of the 21 receptors studied: a clockwise hysteresis was found in those receptors above the carina whereas a counterclockwise one in those below. Results of these studies suggest that the response of PSRs to bronchoconstriction depends on their locations in the tracheobronchial tree.