Electrocardiographic Effects of Reflex Vagal Stimulation

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Abstract
Cats and dogs under ether, Nembutal, Pentothal or Morphine-chloretone were used to investigate the integration of P amplitude and the R-R and P-R intervals. Nonreflex changes in heart rate were induced by warming or cooling the SA node. Reflex changes were induced either by raising the pressure within the carotid sinus according to the method of Wang and Borison, or by manual compression of the exposed sinuses. Continuous eeg''s were taken before and during these procedures. Data were obtained on intact, unilaterally and bilaterally vagotomized, and sympathectomized animals. The results indicate that the integration of the three variables is due primarily to vagal impulses, that section of either vagus produces quantitative changes only, and that sympathectomy does not affect the integration. Cooling of the SA node combined with reflex vagal stimulation gives additive effects upon the changes in P amplitude and R-R interval. The rate of a nodal rhythm, induced by cooling the SA node, may be reduced by carotid sinus stimulation.