Morphologies, dimensions and targets of gastric nitric oxide synthase neurons

Madeleine R Di Natale,John B Furness,Billie Hunne,Linda J Fothergill,Martin J Stebbing,Jamie J M Liew

doi:10.1007/s00441-022-03594-0

Abstract

We investigated the distributions and targets of nitrergic neurons in the rat stomach, using neuronal nitric oxide synthase (NOS) immunohistochemistry and nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry. Nitrergic neurons comprised similar proportions of myenteric neurons, about 30%, in all gastric regions. Small numbers of nitrergic neurons occurred in submucosal ganglia. In total, there were ~ 125,000 neuronal nitric oxide synthase (nNOS) neurons in the stomach. The myenteric cell bodies had single axons, type I morphology and a wide range of sizes. Five targets were identified, the longitudinal, circular and oblique layers of the external muscle, the muscularis mucosae and arteries within the gastric wall. The circular and oblique muscle layers had nitrergic fibres throughout their thickness, while the longitudinal muscle was innervated at its inner surface by fibres of the tertiary plexus, a component of the myenteric plexus. There was a very dense innervation of the pyloric sphincter, adjacent to the duodenum. The muscle strands that run between mucosal glands rarely had closely associated nNOS nerve fibres. Both nNOS immunohistochemistry and NADPH histochemistry showed that nitrergic terminals did not provide baskets of terminals around myenteric neurons. Thus, the nitrergic neuron populations in the stomach supply the muscle layers and intramural arteries, but, unlike in the intestine, gastric interneurons do not express nNOS. The large numbers of nNOS neurons and the density of innervation of the circular muscle and pyloric sphincter suggest that there is a finely graded control of motor function in the stomach by the recruitment of different numbers of inhibitory motor neurons.

Highlights

The movements of the stomach are controlled by enteric excitatory and inhibitory motor neurons, whose activities are co-ordinated through the vagus nerve
NADPH diaphorase (NADPHd) histochemistry showed myenteric ganglia and ganglionic connectives to be present throughout the stomach, except that there was a region along the lesser curvature that contained few ganglia (Fig. 2)
This study shows that nitrergic neurons in the rat stomach supply the longitudinal, circular and oblique layers of the external muscle, the muscularis mucosae and arteries within the Myenteric ganglia Ganglia/mm2

Summary

Introduction

The movements of the stomach are controlled by enteric excitatory and inhibitory motor neurons, whose activities are co-ordinated through the vagus nerve. NNOS is in both inhibitory muscle motor neurons and interneurons, with the interneurons,. There is a polarity in the motor neuron supply, the inhibitory neurons projecting anally before supplying circumferentiallyoriented branches to the muscle, and the excitatory neurons projecting orally before branching in the gastric corpus (Brookes et al 1998). Both structural and functional data indicate that gastric nNOS neurons supply the external muscle, but whether there are nNOS interneurons, or nNOS neurons that supply other targets, is not resolved. We have examined the distributions of nNOS neurons and their terminals throughout the rat stomach in order to answer these questions

Methods

Results

Discussion