Effects of sympathetic stimulation on carotid and aortic baroreceptors in the cat.

Variations in the discharge of baroreceptor units in the left aortic nerve were investigated during stimulation of the stellate ganglion both in the intact cat and in vitro perfusion of the aortic arch. The effects of stimulation of the peripheral cervical sympathetic trunk of the baroreceptor discharge in the carotid nerve during in vitro perfusion of the carotid artery were further studied. Stimulation of the stellate ganglion or the aortic nerve in the intact cat caused a simultaneous increase in arterial pressure, heart rate and number of baroreceptor impulses in a filament to the left aortic nerve. In the in vitro studies, decreases in the number of baroreceptor impulses both in the aortic and carotid nerves were produced in most cases during the stimulation of the sympathetic nerves. These effects were only observed during low pressure perfusion of the isolated artery and in low frequency changes. The infusion of norepinephrine caused a more marked decrease.