Interaction of cardiopulmonary chemoreceptor (Bezold-Jarisch) and somatosympathetic reflexes.

Cardiopulmonary chemoreceptor (Bezold-Jarisch) and baroreceptor reflexes produce similar overall cardiovascular effects although central integrating mechanisms are not identical. In view of recent reports emphasizing the complexity of baroreceptor mechanisms, the influence of both reflexes on spontaneous sympathetic outflow as well as their interaction with the somatosympathetic reflex were compared in anesthetized cats. The chemoreflex and the baroreceptor reflex were activated by i.v. injection of veratrine and norepinephrine, respectively, and both inhibited spontaneous efferent sympathetic nerve traffic. Stimulation of somatic nerves produces a two-component reflex potential in sympathetic nerves. Activation of cardiopulmonary chemoreceptor and baroreceptor reflexes inhibited the amplitude of the initial (spinal) phase of this somasympathetic reflex slightly and greatly attenuated the secondary (supraspinal) component. These experiments demonstrate that the cardiopulmonary chemoreceptor and baroreceptor reflexes exert similar effects on the somatosympathetic reflex and that the former two reflexes may influence sympathetic mechanisms at spinal as well as supraspinal levels.