The effect of pulmonary stretch receptor activity on the respiratory response to ammonia-inhalation

The contribution of pulmonary stretch receptor (SR) activity to the changes in breathing pattern (f, VT, tI, tE, tI: tE) following inhalation of ammonia vapour has been studied in rabbits at three levels of lung distension, i.e., three levels of SR activity, and during reversible SO2-blockade of SR. The result show that the increase in breathing frequency (f) and the decrease in tidal volume (VT) due to ammonia inhalation are almost identical for animals with and without blockade of SR, whereas the duration of inspiration and expiration (tI, tE) as well as their relationship (tI:tE) vary considerably, the variations depending on the level of SR activity. For a given tI the expiration was longer in animals with SR intact than in animals with SR blocked. It is concluded that in rabbits the increased activity of SR after inhalation of ammonia counteracts significantly the predominant effects of irritant (deflation) receptor stimulation, thus rendering possible a longer expiration.