Afferent fibres from the abdomen in the vagus nerves

Abstract

EVIDENcE has recently been advanced of the existence of afferent fibres from the abdomen in the splanchnic nerves [Bain, Irving and McSwiney, 1935]. It is also believed that afferent fibres from the abdomen are present in the vagus nerves, but the evidence in support of the presence of these fibres is unsatisfactory, and in many instances the experimental results reported are contradictory. Thus on the one hand it is stated that there is no evidence for the presence of sensory fibres in the abdominal vagus nerves [Muller, 1911]; while other investigators, working on dogs, have found that when all afferent pathways except the vagi have been eliminated, the abdominal viscera still remain sensitive [Lebedenko and Brjussowa, 1930].Histological studies of the abdominal vagus nerves have been made by Edgeworth [1892], Muller [1911], van Gehuchten and Molhant [1911], and Chase and Ranson [1914]. Heinbecker and O'Leary [1933] have studied the time of conduction of impulses in the vagus nerve, and are of the opinion that all the afferent fibres of the nerve are medullated fibres of the somatic type. Edgeworth also describes large medullated fibres in the abdominal vagus nerves which he regards as sensory in function, but he considers it unlikely that these are the sole sensory fibres in the vagus.Examination of the literature reveals the fact that while a number of investigators have obtained evidence of afferent fibres in the vagus trunks of the abdomen, few of these have set out definitely to investigate the course and pathway of these fibres. The study of afferent fibres in the vagus trunks of the abdomen in all instances has depended upon the elicitation of some reflex response in the animal.

Contractions of the caudal region of the oesophagus of the cat

“…Since these demonstrations were made in decerebrate spinal cord pithed preparations the possibility that the reactions involved afferents which leave the vagus in the thorax and enter the thoracic spinal cord (Harper, McSwiney & Suffolk, 1935) has been avoided.…”

“…The involvement in gastro-oesophageal reactions of vago-vagal reflexes is further indicated by the demonstration of both excitatory and inhibitory responses to afferent vagal stimulation of the abdominal vagus nerve trunks. Since these demonstrations were made in decerebrate spinal cord pithed preparations the possibility that the reactions involved afferents which leave the vagus in the thorax and enter the thoracic spinal cord (Harper, McSwiney & Suffolk, 1935) has been avoided.…”

A study of gastric stretch receptors. Their role in the peripheral mechanism of satiation of hunger and thirst

“…BY A. S. PAINTAL* From the Physiology Branch, Technical Development Establishment Laboratories, Kanpur, India (Received 22 April 1954) A number of investigators have shown that reflex respiratory, pupillary or vascular effects are produced by stimulating the central end of the vagi below the diaphragm (Brodie & Russell, 1900;Neumann, 1914;Carlson & Luckhardt, 1921;Harper, McSwiney & Suffolk, 1935), although these observations do not indicate that nerve fibres of the stomach are involved. However, Irving, McSwiney & Suffolk (1937) have shown clearly from a study of pupillary responses that sensory impulses in the vagus are produced when the stomach is distended.…”

Sensory afferents from the gastrointestinal tract

“…Some viscerotopic organization of the nodose ganglia has been observed in electrophysiological studies (145) but denied in histological studies that used horseradish peroxidase labeling (128). There has been one report of vagal afferent fibers leaving the main thoracic trunks and entering the spinal cord along with intercostal nerves (105).…”