Fluorescence Histochemical Demonstration of Adrenergic Nerve Fibers in the Vagus Nerve of Cats and Dogs

Abstract

The cervial vagus nerves of the mammalians are known to be composed of the fol lowing five, functionally different fibers: 1) general somatic afferent fibers, 2) general visceral afferent fibers, 3) specific visceral afferent fibers, 4) general visceral efferent fibers and 5) specific visceral efferent fibers (1). The general visceral efferent fibers originating from the dorsal motor nucleus of the vagus in the medulla oblongata are regarded to be cholinergic in nature. But fluorescence histochemical studies showed that green-fluores cent noradrenaline terminals became visible in the part of this nucleus after giving 1-dopa to rats (2).Cholinergic impulses conducted in the vagus nerve give rise to the inhibition of cardiac rate and contractility, the relaxation of gastrointestinal sphincters and also to the increase of gastrointestinal motility and tone. However, since the demonstration by McEwen (3) that electrical stimulation of the vagus nerve to the isolated rabbit atria resulted in the increase in cardiac rate and contractility under the presence of hexamethonium, evi dence to confirm the dual responses of the heart to vagal stimulation is accumulating in cats (4), rabbits (5-7) and guinea pigs (8) under various experimental conditions. Jellinek et al. (9) have shown that bilateral cervical vagosympathectomy results in a significant reduction of cardiac catecholamine if dogs survived surgery. The results are rather indicative of the contribution of the vagus nerves to retaining the endogenous noradrenaline in the heart. The demonstration by Hamberger and Norberg (10) that the pelvic nerve of the cat, known to be pure cholinergic in nature, contained the nora drenaline-fluorescent fibers stimulated the authors to perform the present experiments.The vagus nerve of the cat, readily separable from the cervical sympathetic nerve, and also the same nerve of the dog constituting the vagosympathicus were found to contain the noradrenali ne-fluorescent fibers. METHODS

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).…”

Evidence for non‐cholinergic, non‐adrenergic nervous control of mucus secretion into the cat trachea.

“…The second explanation was that during these experiments we may have been stimulating some sympathetic fibres running in the vagus nerves (Ranson,Foley & 342 NERVOUS MEDIATORS OF TRACHEAL SECRETION Alpert, 1933;Muryobayashi, Mori, Fujiwara & Shimamoto, 1968). The increase in heart rate at the onset of vagal stimulation in atropinized cats is evidence for this.…”

Considerations of the Efferent Nervous Mechanism of the Vago-Vagal Reflex Relaxation of the Stomach in the Dog

“…Effects of drugs on the vagal relaxation of the stomach Recently, Muryobayashi et al (15) showed that the cervical vagus and gastric branch in dogs contained green-fluorescent materials representing catecholamines and they concluded that the vagus contained adrenergic components. We attempted to determine whether the adrenergic mecha nism contributes to the incidence of the vagal relaxation of the stomach in atro pinized animals or not.…”