Action Potentials of the “Respiratory Center.”

Abstract

A systematic study of localized potentials lends itself well to the localization of the respiratory center and to an analysis of its still unknown mode of function. After removing the skull cap and the cerebral and cerebellar hemispheres in the dog, we explored the depths of the brain stem from the thalamus through the upper portion of the cervical cord with needle electrodes. A variety of potentials were encountered but in the medulla and upper cervical cord discrete potentials, of orderly sequence, associated with the respiratory act, have been definitely established. These potentials are readily counted and appear to arise from individual nerve cells or neuraxones.

Inspiratory potentials commonly accelerate and deaccelerate with the waxing and waning of inspiration. These potentials cease during the phase of expiration, or continue at a lowered rate during this period. As a rule, the amplitude of discrete potentials remains moderately constant, but instances of gross change of intensity associated with little change in rate have been encountered.

Expiratory potentials during active expiration may accelerate and deaccelerate with waxing and waning of the expiratory act. Usually discrete potentials progress at a uniform rate throughout expiration regardless of its duration indicating a tonic nature of discharge. They are inhibited in rate or number, only during the phase of inspiration. These results fit in with classification of types of breathing previously recorded by the potential method in respiratory muscles of the dog (Gesell).

Central expiratory potentials, of the tonic type, were commonly of a much higher frequency than those previously recorded in respiratory muscles (Gesell), suggesting the existence of a step-down mechanism. There is also some evidence that certain potential frequencies may be a multiple of a lower rate of discharge.