RELATIONSHIP BETWEEN THE SELF-SUSTAINED ACTIVITY OF THE CEREBRAL CORTEX AND THE EFFERENT DISCHARGE OF CARDIAC SYMPATHETIC AND PARASYMPATHETIC FIBERS

Abstract

On paralyzed dogs the electrical activity of the left sympathetic and parasympathetic cardiac nerves was recorded simultaneously with the activity of the cerebral cortex (sigmoid gyri). The electrical activity of the sympathetic postganglionlc fibers (superior cervical and "Stellate" ganglia) increased when the anterior or posterior sigmoid gyri were activated. When a self-sustained activity was evoked in these areas the increase in sympathetic activity lasted as long as the cerebral self-sustained episode. The magnitude of the increase in the sympathetic discharge was in general parallel to the increase in the activity of the anterior sigmoid gyrus. The self-sustained cortical response, evoked by the stimulation of convolutions other than the sigmoid, did not produce by itself changes in either the activity of sympathetic cardiac nerves, the systemic blood pressure, the heart rate or in the pupillary size. Such modifications appeared only when the self-sustained activity spread from the stimulated area to the sigmoid gyri. The pattern of the sympathetic activity of the cardiac nerves showed 2 types of responses (tonic and clonic) which coincided with the tonic-clonic stages recorded from the anterior sigmoid gyrus. The self-sustained activity ended suddenly and at this moment the sympathetic discharge diminished or even was abolished. This reduction in the sympathetic discharge appeared simultaneously with the cessation of self-sustained activity and lasted 2 to 13 seconds. The above mentioned effects were observed after bilateral vagotomy and also when the changes in systemic blood pressure, produced by the cortical self-sustained activity, were minimized by means of a compensator system. The self-sustained cortical activity of the sigmoid gyri produced during the initial part an increase in the vagal discharge which was in general followed by a gradual reduction; at the final part of the self-sustained episode the reduction was so evident that the vagal discharges were abolished. Simultaneously with the abrupt cessation of the self-sustained activity and during the sympathetic inhibition an increase of the vagal activity was observed. The cardiovascular changes observed during the self-sustained cortical activity are discussed considering the relationships between the magnitude and temporal course of sympathetic and parasympathetic efferent discharge.