The role of the vagus nerves, peripheral chemoreceptors and other afferent pathways in the genesis of augmented breaths in cats and rabbits

Abstract

Augmented breaths in cats and rabbits are described in terms of tidal volume, phrenic nerve multifibre discharge and single phrenic motoneurone action potentials. Cyanide and hypoxia (which stimulate peripheral chemoreceptors) can cause augmented breaths but usually only with facilitation from vagal afferent nerves. There is evidence that vagal and cehemoreceptor inspiratory drives sum in the C.N.S. to cause augmented breaths, although a positive feedback (peripheral chemoreceptor activity increasing breathing and thus increasing lung irritant receptor activity) may be involved too. Augmented breaths are also caused by histamine, phenyldiguanide, laryngeal irritation and noxious stimuli. The receptors involved are discussed and it is concluded that several afferent inputs can contribute to causing augmented breaths.