Reflex effects of stimulation of carotid sinus and aortic baroreceptors on hindlimb vascular resistance in dogs

Two series of experiments were performed on anesthetized dogs whose hindlimbs were perfused at constant flow and the blood pressures in the femoral artery, aortic arch, and carotid sinus recorded. The reflex changes in hindlimb vascular resistance were determined in response to changes in pressure in the aortie arch in the first series, and in the carotid sinus in the second. In each series, when one baroreceptor area was stimulated, the other area was eliminated-in the first series, by perfusing the carotid sinuses at constant pressure, and in the second, by vagotomy. The quantitative relationships between hindlimb vascular resistance and pressure at each of the two baroreceptor sites were determined over the low frequency range (0.001-0.1 Hz). The average estimated steady-state gain of the carotid sinus baroreceptor system was 2.22±0.19 (SE) and that of the aortic baroreceptor system 1.06±0.13. The time courses of response for both systems were similar but the aortic baroreceptors were about half as sensitive as the carotid sinus baroreceptors over the entire frequency range.