Respiratory changes induced by the immediate block of nervous conduction in the vagus nerves.

Abstract

A differentiation of vagal respiratory reflexes has been obtained in rabbits by the application of a D.C. current of various intensities to both the vagus nerves. It has been possible to abolish the inflation reflex while Head's paradoxical response to inflation was revealed without eliminating the deflation reflex. The coexistence of Head's paradoxical reflex and the deflation reflex may suggest that these reflex responses originate through activation of the same receptors.The inspiration which follows the immediate withdrawal of vagal afferent inflow has a much longer duration than the following ones: this seems to suggest that some of the inhibitory influence coming through the vagus is taken over, after the duration of the first breath, by some other inhibitory mechanism.A vagal ‘block’ introduced at the same time as an occlusion of the airways leads to an inspiratory effort which is much longer than when occlusion only is performed. This could be ascribed to the blockade of some vagal fibres normally active at FRC which should have an overall inhibitory influence on inspiratory activity.