Response of pulmonary stretch receptors to shifts of functional residual capacity.
The response of slowly adapting pulmonary stretch receptors (PSRs) to sustained elevations of functional residual capacity (FRC) was investigated in spontaneous breathing anesthetized cats. A subatmospheric pressure was produced around the thorax and abdomen to increase FRC by approximately one tidal volume (VT) for up to 60 min. During eupneic breathing the PSR frequency (fPSR) was closely related to changes in transpulmonary pressure (PTP), but occasionally hysteresis was observed in the FPSR - PTP relationship. Elevation of FRC caused most phasic PSRs to discharge continuously for a few breaths before returning to a phasic discharge pattern. During the shift in FRC there were increases in mean fPSR, peak fPSR firing threshold which were sustained throughout the period of elevated FRC. PSRs that normally showed discharges at FRC similarly increased their mean and peak firing rates. For all PSRs the y-intercept (fPSR at PTP = 0) of the fPSR - PTP relationship was decreased but the sensitivity of the PSR as defined by delta fPSR/delta PTP was not changed until the period of elevated FRC exceeded 30 min. Thereafter, PSR sensitivity tended to decline. These results suggest that PSRs undergo some modification of their discharge parameters during prolonged elevation of FRC.
D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D002415:Cats; D004594:Electrophysiology; D005652:Functional Residual Capacity; D008176:Lung Volume Measurements; D008465:Mechanoreceptors / Q000502:physiology*; D011661:Pulmonary Stretch Receptors / Q000502:physiology*