An electron microscope study of vagus nerve composition in the ferret

Asala, Samuel; Bower, Adrian J.

doi:10.1007/bf00389602

Cited by 45 publications

(31 citation statements)

References 19 publications

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“…This distribution matches that reported by Fahrenkamp and Friede (1987) on the rat, and is also very similar to the distribution reported on the abdominal vagus of the pigeon (Schwaber and Cohen (1978). The distributions of myelinated abdominal vagal fibers in the cat (Agostoni et al 1957;Mei et al 1980) and the ferret (Asala and Bower 1986) are also similar but shifted a little to the right (larger fibers); all of the fibers are less than 6 txm and most are between 2 and 4 lain.…”

Section: Electron Microscopysupporting

confidence: 89%

The fiber composition of the abdominal vagus of the rat

1990

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The present study provides a LM and EM inventory of the fibers of the rat abdominal vagus, including dorsal and ventral trunks and the five primary branches. Whole mounts (n = 15) were prepared to characterize the branching patterns. A set of EM samples consisting of both trunks and all branches (i.e. dorsal and ventral gastric, dorsal and accessory celiac, and hepatic) were then obtained from each of six additional animals. A complete cross-sectional montage (x 10000) was prepared from each sample. All axons were counted, and greater than 10% of them were evaluated morphometrically. The means of unmyelinated axon diameters for each of the five branches were similar (0.75-0.83 microns). However, the shapes of the fiber size distributions, as summarized by their skew coefficients, revealed that the two gastric branches differed significantly from the two celiac branches; furthermore, the hepatic size distribution differed from all others. Most of the myelinated fibers (85%) in all branches were less than 2.6 microns in diameter and had sheath widths between 0.1 and 0.5 micron. The gastric branches, however, also contained a few larger myelinated fibers with sheath widths as great as 0.85 micron. Whole mounts revealed fibers which were not of supradiaphragmatic origin within all five vagal branches; these adventitial bundles were traced along the perineurium between adjacent branches. The sum of the fibers in the five branches (26930) was 21% more than the number counted in the parent trunks (22272); this excess probably reflects the adventitial fiber content. The whole mounts also showed that a large and regularly positioned paraganglion was associated with the dorsal branches. The structural profiles observed (i.e. unmyelinated and myelinated fibers size distributions, presence of extrinsic fascicles, glomus tissue content, etc.) differentiate the vagal branches into three morphologically distinct sets: a gastric pair, a celiac pair, and a hepatic branch. The fiber counts, when considered with observations of the numbers of efferents and adventitial fibers in the nerve, suggest that the percentage of efferent fibers is much higher than in all the widely accepted estimates found in the literature: efferent fibers may represent over a quarter of the total number of fibers.

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Section: Electron Microscopysupporting

confidence: 89%

The fiber composition of the abdominal vagus of the rat

1990

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“…The subdiaphragmatic vagal trunks and their various branches are made up of mainly sensory fibers, accounting for ~75–90% of the total fiber population (Asala and Bower, 1986; Prechtl and Powley, 1990). Most of the fibers are unmyelinated, and they originate from neurons in the nodose ganglion.…”

Section: Discussionmentioning

confidence: 99%

Gastric afferents project to the aldosterone-sensitive HSD2 neurons of the NTS

Shin

Loewy

2009

Brain Research

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The HSD2 (11-β-hydroxysteroid dehydrogenase - type 2 enzyme) containing neurons of the nucleus tractus solitarius (NTS) become activated during low-sodium and high-aldosterone states such as hypovolemia. This response may be due to hormonal and/or neural signals. Hormonal signals may activate neurons in the area postrema that innervate the HSD2 neurons. The vagus nerve projects directly to the HSD2 neurons and this could be another route whereby these neurons receive information about systemic sodium/aldosterone status. The peripheral sites of origin that contribute to this vagal projection remain unknown, and in the present study, we injected the transganglionic tracer, cholera toxin β-subunit-horseradish peroxidase (CTb-HRP), into wall of various gastrointestinal organs (stomach, small and large intestine) or liver of rats. Confocal microscopy of brainstem sections stained by a double immunohistochemical procedure was used to analyze whether the HSD2 neurons received axonal contacts from specific gastrointestinal structures. The major source of afferents arose from the stomach, mainly from its pyloric antrum, but a weaker input originated from the fundus region. A trace amount originated from the duodenum. The terminal part of the small intestine and large intestine did not to contribute to this projection. Similarly, no afferent inputs from the liver or portal vein were found. In conclusion, HSD2 neurons receive an input mainly from the stomach and these results are considered as potential sites affecting sodium intake.

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“…To assess the direction of the current, we studied anesthesia parameters in group C. The vagus nerve is a mixed nerve consisting of motor and sensory fibers; most the sensory fibers are afferent nonmyelinated fibers (15). Ninety percent of the total abdominal vagus is made up of afferent fibers (16). The motor component of the vagus is involved in gastric secretion and empying and adaptative relaxation.…”

Section: Discussionmentioning

confidence: 99%