Abstract
OBJECTIVES:Baroreflex activation therapy (BAT) is a novel therapy that utilizes electrical field stimulation of the carotid sinus nerve to reduce blood pressure in patients with resistant hypertension. Electrical stimulation of the baroreceptor afferents via the aortic depressor nerve (ADN) in rats may bring new insights into the mechanisms underlying BAT. In this study, we examine cardiovascular responses to electrical stimulation of the left versus right ADN in spontaneously hypertensive rats (SHR).
METHODS:Male pentobarbital-anesthetized SHRs (25–27 weeks, n = 8–9) were instrumented for right and left ADN stimulation (1–40 Hz, 0.2 ms, 0.4 mA for 20 s) and recording of mean arterial pressure (MAP), heart rate (HR) and mesenteric (MVR) and femoral (FVR) vascular resistance.
RESULTS:Both right and left ADN stimulation evoked frequency-dependent (P < 0.001) drops in MAP, HR, MVR and FVR (Fig. 1). However, stimulation of the left ADN evoked greater (P < 0.001) reflex depressor and bradycardic responses and preferential reductions in FVR (hindquarter) over MVR relative to the stimulation of the right side (Fig. 1).
CONCLUSION:Enhanced hypotensive responses to left ADN stimulation are likely due to more potent baroreflex-mediated reductions in HR and vascular resistance relative to the right ADN. These results show a differential central processing of afferent neurotransmission promoted by the left versus right ADN. Clinically, this may have implications in fine-tuning the magnitude of BAT-driven blood pressure drop in patients in relation to the severity and chronicity of hypertension. Further studies are required to understand the mechanisms responsible for differences in the central integration of left versus right afferent input.