Modulation of renal baroreceptor function by catecholamines and salt intake in the conscious dog

We have examined the relationship between plasma renin activity and renal perfusion pressure by determining the stimulus-response curve of the renal baroreceptor in conscious, uninephrectomized dogs, and the modulation induced by catecholamines and varying salt intake. Renal perfusion pressure was controlled by step-wise inflation of a constricting cuff previously implanted around the renal artery. The stimulus-response curve of the renal baroreceptor may be divided into two ranges: a relatively flat portion close to normal pressure (100 mmHg), and a much steeper section below a "threshold" pressure of 75-80 mmHg. Epinephrine (I.V. or I.R.) produced a parallel shift of the curve to the right, i.e., a smaller drop in pressure was needed to reach "threshold." Changing the diet from normal salt intake (80 meq/day) to a low salt intake (10 meq/day) increased the gain of the stimulus-response curve. Thus, the same elevated PRA may be reached either by a shift of the curve to the right, or by increase in gain.