Modification of carotid baroreceptor function by electrical stimulation of the ganglioglomerular nerve

The effect of ganglioglomerular nerve (GN) stimulation on canine carotid baroreceptors has been investigated. In the first group of experiments, a reflex response of the mean arterial blood pressure (MAP) was observed, MAP decreased during GN stimulation. The time-course and magnitude of the pressure decrease were dependent upon the stimulus frequency. In a second experimental group, isolated carotid bifurcations were continuously perfused with arterial blood (at constant flow rate) and changes in the perfusion pressure were used as an indicator of vessel wall reaction to GN stimulation. The vessel wall response began 15-20 sec after onset of the stimulation and a steady-state level was reached again after about 100 sec of stimulation. In a third group of experiments, the carotid baroreflex was investigated during periods with and without stimulation of the GN. During GN stimulation the magnitude of reflex responses was reduced, the working range of the baroreceptors displaced and the input-output relationship shifted towards lower intrasinus pressure values. From these findings it is concluded that efferent sympathetic activity (ESA) in the GN supplying the carotid bifurcation, affects the baroreceptor reaction in two ways: (i) by a short-lasting increase in baroreceptor sensitivity due to their direct influence; and (ii) by a more sustained and much slower-acting mechanism mediated by vessel wall stiffness (compliance) change (indirect influence).