Effects of different input pressure waveforms on the carotid sinus baroreflex-mediated sympathetic arterial pressure response in rats

Abstract

Although the pulsatility of an input pressure is an important factor that determines the arterial baroreflex responses, whether the difference in the input waveforms can meaningfully affect the baroreflex function remains unknown. This study aimed to compare baroreflex responses between two distinct pressure waveforms: a forward saw wave (FSW) and a backward saw wave (BSW). In seven anesthetized rats, carotid sinus pressure was exposed to the FSW or the BSW with a mean of 120 mmHg, pulse pressure of 40 mmHg, and pulse frequency of 1 Hz. Changes in efferent sympathetic nerve activity (SNA) and arterial pressure (AP) during six consecutive saw wave trials (FSW₁, BSW₁, FSW₂, BSW₂, FSW₃, and BSW₃) were examined. The steady-state SNA value during FSW₁ was 91.1 ± 1.9%, which was unchanged during FSW₂ and FSW₃ but significantly increased during BSW₁ (106.6 ± 3.4%, P < 0.01), BSW₂ (110.6 ± 2.5%, P < 0.01), and BSW₃ (111.6 ± 2.3%, P < 0.01). The steady-state AP value during FSW₁ was 98.2 ± 8.1 mmHg, which was unchanged during FSW₂ and FSW₃ but significantly increased during BSW₁ (106.7 ± 7.4 mmHg, P < 0.01), BSW₂ (105.6 ± 7.8 mmHg, P < 0.01), and BSW₃ (103.8 ± 7.2 mmHg, P < 0.05). In conclusion, the FSW was more effective than the BSW in reducing mean SNA and AP. The finding could be applied to designing an artificial pulsatile pressure such as that generated by left ventricular assist devices.NEW & NOTEWORTHY This study examined whether the waveforms of an input pressure alone can affect the baroreflex function by using a forward saw wave and a backward saw wave with the same mean pressure, pulse pressure, and pulse frequency. The forward saw wave was more effective than the backward saw wave in reducing sympathetic nerve activity and arterial pressure. The finding could be applied to designing an artificial pulsatile pressure such as that generated by left ventricular assist devices.

Keywords: carotid sinus baroreflex; open-loop analysis; pulsatility; simulation; sympathetic nerve activity.