Sympathetic nerve fibers and ganglia in canine cervical vagus nerves: Localization and quantitation

Abstract

Background Cervical vagal nerve (CVN) stimulation may improve left ventricular ejection fraction in patients with heart failure. Objectives To test the hypothesis that sympathetic structures are present in the CVN and to describe the location and quantitate these sympathetic components of the CVN. Methods We performed immunohistochemical studies of the CVN from 11 normal dogs and simultaneously recorded stellate ganglion nerve activity, left thoracic vagal nerve activity, and subcutaneous electrocardiogram in 2 additional dogs. Results A total of 28 individual nerve bundles were present in the CVNs of the first 11 dogs, with an average of 1.87 ± 1.06 per dog. All CVNs contain tyrosine hydroxylase-positive (sympathetic) nerves, with a total cross-sectional area of 0.97 ± 0.38 mm2. The sympathetic nerves were nonmyelinated, typically located at the periphery of the nerve bundles and occupied 0.03%–2.80% of the CVN cross-sectional area. Cholineacetyltransferase-positive nerve fibers occupied 12.90%–42.86% of the CVN cross-sectional areas. Ten of 11 CVNs showed tyrosine hydroxylase and cholineacetyltransferase colocalization. In 2 dogs with nerve recordings, we documented heart rate acceleration during spontaneous vagal nerve activity in the absence of stellate ganglion nerve activity. Conclusions Sympathetic nerve fibers are invariably present in the CVNs of normal dogs and occupy in average up to 2.8% of the cross-sectional area. Because sympathetic nerve fibers are present in the periphery of the CVNs, they may be susceptible to activation by electrical stimulation. Spontaneous activation of the sympathetic component of the vagal nerve may accelerate the heart rate.

The strange case of the ear and the heart: The auricular vagus nerve and its influence on cardiac control

“…Similar sympathetic structures have previously been observed in the canine cervical vagus nerve, although the fibres were distributed to the periphery of the nerve (Onkka et al, 2013). This apparent evolutionary vestige is in line with other species where sympathetic and vagus fibres may be transmitted to the thorax via a common trunk (Muryobayashi et al, 1968;Onkka et al, 2013). In addition, anatomical studies have documented rich interactions between the right thoracic vagal nerve and the right stellate ganglion at all levels (Ellison et al, 1969;Mizeres, 1955) and the rat superior cervical ganglia have been found to contain bundles of nerve fibres derived from the vagus nerve that are immunoreactive for calcitonin gene-related peptide and substance P (Zaidi et al, 2013).…”

“…Moreover, Verlinden and colleagues found that the human right cervical vagus contains around twice as many sympathetic fibres as the left cervical vagus (Verlinden et al, 2016). Similar sympathetic structures have previously been observed in the canine cervical vagus nerve, although the fibres were distributed to the periphery of the nerve (Onkka et al, 2013). This apparent evolutionary vestige is in line with other species where sympathetic and vagus fibres may be transmitted to the thorax via a common trunk (Muryobayashi et al, 1968;Onkka et al, 2013).…”

Effects of stepwise denervation of the stellate ganglion: Novel insights from an acute canine study

“…They have a strong sympathetic output, as demonstrated by Norris et al 20 We observed that the ansae subclaviae directly innervate the vagal trunk, as reported previously. 18,21,22 Sheikh-Zade et al reported that in acute experiments on cats, stimulation of the ansae subclaviae potentiated the effects of vagal stimulation.…”

Atrial Structure and Function and its Implications for Current and Emerging Treatments for Atrial Fibrillation

“…Broadly, parasympathetic and sympathetic inputs are mediated via the vagal nerve and stellate ganglion respectively, although considerable overlap exists. 32 Intrinsic parasympathetic and sympathetic neural inputs are heavily co-localised with up to 30% having dual adrenocholanergic properties -making selective targeting of autonomic activity by localised ablation difficult. By far most intrinsic cardiac nerve complexes are located in the atria, often congregating in known arrhythmogenic 'hot spots' such as the PV/LA junction and have been heavily implicated in arrhythmogenesis.…”