Vagal afferent innervation of smooth muscle in the stomach and duodenum ofthe mouse: Morphology and topography

Intraganglionic laminar endings (IGLEs) and intramuscular arrays (IMAs), th e two putative mechanoreceptors that the vagus nerve supplies to the gastro intestinal smooth muscle, have been characterized almost exclusively in the rat. To provide normative inventories of these afferents for the mouse, th e authors examined the endings in the stomach and small intestine of three strains used as backgrounds for gene manipulations (i.e., C57, 129/SvJ, and WBB6). Animals received nodose ganglion injections of wheat germ agglutini n-horseradish peroxidase or dextran-tetramethylrhodamine conjugated to biot in. The horseradish peroxidase tissue was processed with tetramethylbenzidi ne and was used to map the distributions and densities of the two endings; the dextran material was counterstained with c-Kit immunohistochemistry to assess interactions between intramuscular arrays and interstitial cells of Cajal. IGLEs and IMAs constituted the vagal innervation of mouse gastric an d duodenal smooth muscle. IGLE morphology and distributions, with peak dens ities in the corpus-antrum, were similar in the three strains of mice and c omparable to those observed in rats. IMAs varied in complexity from region to region but tended to Lt simpler (fewer telodendria) in mice than in rats . IMAs were most concentrated in the forestomach and sphincters in mice, as in rats, but the topographic distributions of the endings varied both betw een strains of mice (subtly) and between species (more dramatically). IMAs appeared to make appositions with both interstitial cells and smooth. muscl e fibers. This survey should make it practical to assay the effects of gene tic (e.g., knockout) and experimental (e.g., regeneration) manipulations af fecting visceral afferents and their target tissues. (C) 2000 Wiley-Liss, I nc.