Inferior cardiac nerve activity in the cat during occlusion of the mesenteric artery

A number of studies in this and other laboratories using hemodynamic and pharmacologic evidence have suggested that occlusion of the mesenteric artery evokes a pressor reflex initiated by mesenteric baroreceptors. To provide additional evidence in support of this hypothesis, neurophysiological recordings were made of inferior cardiac nerve activity during mesenteric artery occlusion (MAO). The results indicate that MAO enhances inferior cardiac nerve activity in the cat, providing that the carotid sinus nerves have been cut. Cutting of the mesenteric nerves further facilitates cardiac nerve activity and abolishes the response to mesenteric artery occlusion. The evidence suggests that MAO evokes a reflex sympathetic discharge which is subject to override by the carotid sinus depressor reflex. The afferent limb of the reflex is characterized by a tonic depressor outflow from the mesenteric pressure receptors.