Factors Affecting Responses of the Inspiratory Center to Electrical Stimulation

Abstract

The responses of the so-called inspiratory center of the anaesthetized cat to electrical stimulation were studied. Responses to increasing stimulus strength showed a progressive shift of the midposition to the inspiratory side, progessive increase in rate and diminution in amplitude of respiration, progressively later breakthrough of spontaneous respiration. Vagotomy increased the electrical excitability of the center; vagal stimulation decreased it. Admn. of CO2 had little effect on excitability, while it increased respiratory rhythmicity. Occlusion of carotids increased excitability, section of cervical dorsal columns decreased it. Section or block of dorsal roots C8 and T1 led to respiratory failure in 4 of 6 vagotomized animals. It is concluded that respiratory rhythmicity may arise from the interrelationship of various feedback systems and be independent of any single intrinsically rhythmic "center".