Modification of Apneusis by Afferent Vagal Stimulation

Abstract

The relative phases of apneusis and apnea varied according to the level of trans-ection of the upper rhombencephalon in vagotomized rabbits. Eupnea was seen at times superimposed on apneusis. Eupnea replaced apneusis after transection just below the acoustic tubercles. The effect of afferent vagal stimulation on apneusis depended on the frequency of stimulation: low frequencies prolonged apneusis, medium frequencies produced rhythmic breathing sustained for the period of stimulation, higher frequencies produced respiratory apnea. Apneusis was prolonged following vagal inhibition. Midline ablation of the upper rhombencephalon slowed apneustic breathing and the eupnea produced by vagal stimulation. Apneusis and apnea are considered to be generated in a region laterally placed at the level of entry of the 8th nerves. The vagus is proposed to act at this level in modifying apneusis.