Different subpopulations of cholinergic and nitrergic myenteric neurones project to mucosa and circular muscle of the guinea-pig gastric fundus

Abstract

Since the stomach lacks a well-developed ganglionated submucous plexus, the somata of enteric neurones innervating the muscle or the mucosa have to be localised within the myenteric plexus. The aim of this study was to determine the projection pathways and the neurochemical coding of myenteric neurones innervating these different targets in the gastric fundus. Myenteric cell bodies projecting to the mucosa or the circular muscle were retrogradely labelled by mucosa or muscle application of the fluorescent tracer DiI and subsequently characterised by their immunoreactivity for choline acetyltransferase (ChAT), nitric oxide synthase (NOS), substance P (SP) and/or neuropeptide Y (NPY). On average 14391 and 8949 myenteric neurones were labelled from the mucosa and the circular muscle, respectively. DiI-labelled neurones were either ChAT-or NOS-positive. DiI-labelled ChAT-positive neurones were mainly ascending and outnumbered NOS-positive neurones, which were mainly descending (79.36.2% vs 20.76.2% for mucosa neurones; 69.311.1% vs 30.711.1% for muscle neurones). Three ChAT-positive subpopulations (ChAT/±, ChAT/SP, ChAT/NPY) and two NOS-positive subpopulations (NOS/±, NOS/NPY) were found. ChAT/SP neurones projected mainly to the circular muscle (36.111.9% of the cholinergic muscle neurones; mucosa projection: 8.02.1%), whereas ChAT/NPY neurones projected mainly to the mucosa (38.19.2% of the cholinergic mucosa neurones; muscle projection: 5.72.4%). NOS/± cells projected predominantly to the muscle. This study demonstrates polarised pathways in the myenteric plexus consisting of ascending ChAT and descending NOS cells that innervate the circular muscle and the mucosa of the gastric fundus. The ChAT/SP neurones might function as circular muscle motor neurones, whereas ChAT/NPY neurones might represent secretomotor neurones.

Neuronal activation of brain vagal-regulatory pathways and upper gut enteric plexuses by insulin hypoglycemia

“…The GI smooth muscle and mucosal layers are directly innervated by enteric plexuses (14,50). Consistent with the strong gastric acid-and motor-stimulatory effects of insulin hypoglycemia, as expected, we observed remarkable Fos expression in the myenteric and submucosal plexuses of the corpus, antrum, and duodenum in rats treated with insulin.…”

“…This caudal raphe-DVC pathway plays an important role in vagalmediated stimulation of gastric functions by cold stress (6,70,71). Peripherally, the gastric and duodenal enteric plexuses, which innervate smooth muscle/mucosal layers and play important roles in regulating gastric and duodenal secretion and motility (14,50), receive a dense and intricate network of vagal efferent axons (2,19,77). Studies on the neuronal responses to abnormal blood glucose levels in these central vagal-regulatory pathways and the vagal-innervated GI enteric plexuses will provide important information regarding the pathophysiological mechanisms of diabetes-induced GI disorders as well as the hypoglycemia-induced activation of gastric/duodenal functions.…”

Distribution and biological activity of obestatin in the rat

“…Our observation coupled with the earlier finding of co-expression of ghrelin immunoreactivity and ChAT (Xu et al 2005) raise the possibility that a majority of cholinergic neurons of the myenteric plexus contain both obestatin and ghrelin. A large percentage of ChAT-containing neurons in the myenteric plexus are secretomotor neurons, though some are thought to be intrinsic primary afferent neurons (Pfannkuche et al 1998, Sang & Young 1998, Mann et al 1999. It remains to be determined whether or not obestatin is distributed in ChAT-positive secretomotor or primary afferent neurons or both.…”

Mucosa of the guinea pig gastric corpus is innervated by myenteric neurones with specific neurochemical coding and projection preferences

“…The tissue culture and retrograde neuronal tracing methods have been previously described in detail (Pfannkuche et al, 1998b;Neunlist and Schemann, 1997). Briefly, adult guinea pigs of either sex (300-600 g) were killed by cervical dislocation followed by exsanguination (a protocol approved by the Animal Welfare Department of the School of Veterinary Medicine, Hannover, and conforming to guidelines of the National Institutes of Health, Bethesda, MD).…”

“…Recently, we were able to demonstrate directly that the gastric mucosa receives a prominent intrinsic innervation by ascending acetylcholine and, to a lesser extent, by descending nitric oxide synthesising myenteric neurones (Pfannkuche et al, 1998b;Reiche and Schemann, 1998). Both acetylcholine and nitric oxide influence acid, bicarbonate, pepsin, and mucus secretions (Fandriks, 1986;Raufman, 1992;Brown et al, 1993a,b;Bilski et al, 1994;Price et al, 1994;Hersey and Sachs, 1995), motility of the muscularis mucosae (Angel et al, 1983;Dobreva et al, 1994), and blood flow (Chen and Guth, 1995;Ohno et al, 1995).…”