Sympathetic Nerve Fibers within the Cervical Vagus Nerve Do Not Innervate the Heart

Abstract

IntroductionChronic cervical vagus nerve stimulation has been introduced as a novel therapy for various diseases, including refractory epilepsy and chronic heart failure. Although it has been shown that the cervical vagus nerve contains sympathetic fibers, whether or not these sympathetic fibers innervate the heart is a subject of debate.MethodsDiI, a plasma membrane lipophilic fluorescent dye (neuronal tracer) was applied on the epicardial surface of the heart at the right atrium‐right pulmonary vein junction and at the inferior vena cava and left atrium junction (these locations are known to have epicardial ganglia) in 4 rats to trace the nerve fibers innervating the heart. Two rats without DiI application served as controls. Right cervical vagus nerves were harvested 1 week after DiI application or sham surgery and processed for frozen histological sections. All sympathetic fibers in the cervical vagus nerve were visualized by immunostaining with anti‐tyrosine hydroxylase antibody, whereas those nerve fibers innervating the heart were expected to carry a fluorescent DiI dye.ResultsAs shown in the figure, there were a few fibers stained with DiI (red color) in the cervical vagus nerve, which were not detected in controls. Sympathetic fibers in the vagus nerve (green color) were present in all animals. However, there was no overlap of the sympathetic fibers and DiI labeled nerve fibers in the vagus nerve.ConclusionsCervical vagus nerve contains sympathetic nerve fibers, however, these fibers do not innervate the heart.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.