Stretch receptor activity during irritant-induced tachypnoea in the rabbit.

The activity in single vagal fibres arising from lung stretch receptors was recorded in rabbits during normal breathing at rest and during tachypnoea caused by inhalation of histamine or ammonia. The rate of argon elimination from the lungs was analysed to estimate the accompanying changes of lungs ventilation. The results show that the majority of stretch receptors increased their activity during irritant-induced tachypnoea, the discharge frequency being always higher inspiration than during expiration. Only a few fibres did not change or decreased their activity. The comparison of the results with previous findings in guinea-pig revealed that the discharge pattern of stretch receptors following inhalation of irritants was different in these two species, whereas the respiratory reactions and the unevenness of ventilation were comparable. It is suggested that the differences in the discharge pattern of stretch receptor fibres during irritant-induced hyperpnoea in rabbit and guinea-pig are due to differences in the location of the stretch receptors concerned.