Splanchnic slowly adapting mechanoreceptors with punctate receptive fields in the mesentery and gastrointestinal tract of the cat

Abstract

SUMMARY1. A class of slowly adapting mechanoreceptors with A-delta and C fibres running in the splanchnic nerves of cats is described.2. The mechanoreceptors have punctate regions of mechanical sensitivity at macroscopic vascular branching points and have been found in the lesser omentum, the mesentery of the gall-bladder, porta hepatis, portal vein, pancreas, spleen and the duodenum, jejunum, ileum, colon and their mesenteries.3. The receptive fields of these mechanoreceptors vary considerably in size in the different regions. The largest receptive fields were found in the small intestinal mesentery and consisted of up to seven points of mechanical sensitivity at vascular divisions, each separated by distances of a few up to about 40 mm. The smallest receptive fields were single or double points of mechanical sensitivity which were most commonly found in relation to the portal vein in the root of the mesentery.4. Maintained stretch of the receptive field elicited a train of impulses which had phasic and tonic components. The tonic discharge was sometimes maintained for more than 1 min.5. Distension of a neighbouring viscus often caused a discharge which had a phasic component and a variable tonic component. The occurrence of the latter appeared to depend on the relative positions of the bowel and mesentery, and was probably associated with a change in tension on the mesentery.6. Occlusion of the portal vein resulted in some units in a discharge which began soon after the start of the occlusion.7. The receptors do not appear to be affected by acid, hypoxia or hypercapnia.

Mucosal receptors in the gastric antrum and small intestine of the rat with afferent fibres in the cervical vagus.

“…Punctate stimulation of the mucosa with a fine bristle rarely excited the endings to the same extent as has been described for other types of abdominal visceral endings (Morrison, 1973). They were insensitive to compression, sustained pressure and distension of the viscus with fluid or air although balloon distension evoked an on-off response (Fig.…”

In vitro recordings of afferent fibres with receptive fields in the serosa, muscle and mucosa of rat colon

“…Blumberg et al 1983;Haupt et al 1983), but not others (e.g. Morrison, 1973). Because our preparation included only the distal colon with little attached mesentery, it is not possible to make direct comparison because connections to other receptive fields on adjacent organs may have been severed.…”

Extrinsic primary afferent signalling in the gut

“…46,81 Similar afferent endings have been confirmed in other regions of the gut in several species. [82][83][84] These vascular afferent endings are also associated with other viscera, including the spleen, ovary, bladder and pancreas. 85 Endings of this type are sensitive to ischaemia, hypoxia and capsaicin, [86][87][88] and they are believed to comprise a major type of nociceptor.…”