New insights into the influence of pulsatile pressure on the arterial baroreceptor reflex.

Pulsatile arterial pressure as compared to static pressure has important influences on baroreceptor activation and on the central mediation of the baroreflex. First, the static pressure-baroreceptor activity curve is sigmoid and the slope or gain peaks abruptly at pressures near 100 mmHg. In contrast, the pulsatile pressure-activity curve is linear over a wide range of pressure and the maximum gain is reduced. Second, exposure of baroreceptors to elevated levels of static pressure causes a rapid resetting or desensitization of the receptors within minutes. Baroreceptor resetting is absent or blunted when the elevated pressure is pulsatile. Third, inhibition of sympathetic activity is greater during pulsatile vs. static pressure even when baroreceptor activity per unit time is less. This central facilitation of the baroreflex is related to the lack of adaptation of central neurons to the pulse phasic afferent activity. The results indicate: 1) the extended linear range of the pressure-activity relation during pulsatile pressure may enable the baroreceptors to accurately detect changes in arterial pressure over a wider pressure range than that predicted from experiments using static pressure; and 2) pulsatile pressure can reduce resetting and promote reflex inhibition of sympathetic activity both by sensitizing the baroreceptors and by centrally facilitating the reflex.