The composition of the vagus nerve of the cat

Abstract

The number and caliber of myelinated and non-myelinated fibers of entire and sensory vagal nerves of cats were studied by means of light and electron miscroscopy. The results obtained with electron microscopy show that the non-myelinated component is particularly rich (about 40,000 elements at the cervical level), with clearly higher numbers of fibers than demonstrated thus far with light microscopy. The ratio of myelinated to non-myelinated fibers is on the average 1:4 for the total vagi and only 1:8 for the sensory vaga component. The comparison of the nerve above and below the level of the nodose ganglion shows that (1) mean fiber diameter is usually greater at the infranodose than at the supranodose level, and (2) some myelinated fibers of small diameter occurring below the nodose ganglion become non-myelinated above it. Additionally, the number of non-myelinated fibers per Schwann cell is greater at the supranodose than at the infranodose level; this speaks in favor of a reorganization of the C-fiber population from one level to the other.

Organization of synaptic transmission in the mammalian solitary complex, studied in vitro.

“…Extracranially, the vagus and glossopharyngeal nerves contain sensory fibres with a wide range of diameters and conduction velocities (Paintal, 1973;Mei, Condamin & Boyer, 1980). In the slice preparation, the conduction distance is very short, and thus temporal dispersion in the arrival of afferent impulses resulting from differences in conduction velocities is likely to be minimal and will not influence the time course of the early e.p.s.p.…”

TRPA1 Channels Mediate Cold Temperature Sensing in Mammalian Vagal Sensory Neurons: Pharmacological and Genetic Evidence

“…In contrast, many vagal afferents do not evoke conscious sensations but can trigger powerful regulatory reflexes that are critical for visceral homeostasis (Paintal, 1973). Most vagal axons are unmyelinated, conducting action potentials in the C-fiber range (Mei et al, 1980;Li and Schild, 2002;Bielefeldt et al, 2006). Vagal afferents are free nerve endings and the majority are polymodal, responding to physical stimuli (mechanical and thermal) and chemical irritants (Higashi, 1986;Carr and Undem, 2003;Lennerz et al, 2007).…”

Two types of gastric excitatory responses to stimulation of the vagal trunk in cats: Efferent and afferent responses.

“…Recent electron microscopic studies have shown that the composition of afferent fibers in the vagal trunk of cats is more than 90% of the total fibers (5).…”