Hemodynamic responses to magnetic stimulation of carotid sinus in normotensive rabbits.

OBJECTIVES: Carotid baroreflex plays a crucial role in regulating arterial pressure. Based on this knowledge, electrical stimulation of carotid sinus was designed for treating resistant hypertension. However, the clinical implication of electrical stimulation of carotid sinus is largely restrained due to obvious invasiveness. This study aimed to evaluate the efficacy of magnetic stimulation of carotid sinus (MSCS), a noninvasive strategy, for lowering blood pressure in rabbits.

METHODS: MSCS with graded intensities and frequencies were systematically attempted in normotensive rabbits. Blood pressure was recorded dynamically. Sinoaortic denervation and plasma hormone level analyses were performed.

RESULTS: When the right carotid sinus was stimulated at 1 Hz frequency, a dose-effect relationship was observed between stimulation intensity (100-250% motor threshold) and mean arterial pressure (MAP) decrement (3.6 ± 1.0 to 10.4 ± 2.3 mmHg). When stimulation intensity was fixed at 200% motor threshold, the median reduction of MAP in 1-Hz group [10.8 (8.6-14.9) mmHg] was significantly higher than that in other frequency groups (all P < 0.05). Heart rates declined transiently after the initiation of MSCS. Compared with baseline (33.9 ± 5.5 pg/ml), plasma epinephrine level increased during MSCS (88.1 ± 9.6, P = 0.002). After ipsilateral sinoaortic denervation, MAP decrement (7.0 ± 0.8 mmHg) was remarkably blunted compared with that in sham animals (13.0 ± 1.1 mmHg, P = 0.001).

CONCLUSION: The current study demonstrated that MSCS treatment can lower the arterial pressure in normotensive rabbits. This preliminarily result warrants further studies to establish the efficacy of MSCS in treating refractory hypertension.