Effect of bronchoconstriction on the firing behavior of pulmonary stretch receptors.

To study the effect of bronchoconstriction on the activity of pulmonary stretch 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 (fPSR) and the transpulmonary pressure (Ptp) was examined during both constant volume ventilation and hyperinflation. During bronchoconstriction, the peak fPSR for the same tidal volume increased significantly (P less than 0.05) compared to the control response obtained with saline aerosols. However, the fPSR at functional residual capacity decreased in the receptors above the carina but increased in those below. Bronchoconstriction induced a hysteresis in the dynamic Ptp-fPSR 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.