Cardiovascular and Autonomic Effects of Auricular Vagus Nerve Stimulation in an Anesthetized Rat Model.

HYPOTHESIS: Electrical stimulation of the external ear mediates cardiovascular changes in anesthetized rats.

BACKGROUND

Auricular vagus nerve stimulation (aVNS) has been proposed as a noninvasive treatment for cardiovascular disease. Stimulation is typically achieved via electrodes placed on the external ear, but the exact mechanisms by which aVNS induces cardiovascular changes remains unclear. In particular, the relative contributions of sympathetic and parasympathetic pathways have not been well elucidated. In this study, we use a rodent model to determine the hemodynamic effects of stimulating two auricular regions and assess the autonomic pathways mediating these responses.

METHODS

Bipolar transcutaneous electrical stimulation was applied to the external ear of adult Sprague-Dawley rats. Cardiovascular parameters including mean arterial pressure (MAP), photoplethysmography (PPG), and cardiac electrical activity were recorded. Cervical vagotomies and hexamethonium sympathetic blockade were performed to assess the parasympathetic and sympathetic contributions to evoked cardiovascular responses.

RESULTS

Electrical stimulation at the concha resulted in significant changes in MAP and PPG. MAP changes were larger with stimulation in the concha compared with the anterior pinna. MAP responses increased in a dose-dependent manner with increasing current amplitude. Bilateral vagotomy resulted in persistent but decreased evoked cardiovascular responses. Complete autonomic blockade using intravenous hexamethonium resulted in the absence of any evoked cardiovascular responses with aVNS.

CONCLUSION

Cardiovascular changes from aVNS are mediated by modulation of both parasympathetic and sympathetic activity.