The co-localization of neuropeptides in the submucosa of the small intestine of normal Wistar and non-diabetic BB rats.

Immunocytochemical double and triple staining techniques were employed on whole mounts of the submucosal plexus from normal Wistar and non-diabetic BB rat jejunum and ileum, to determine the patterns of co-localization of vasoactive intestinal polypeptide-, peptide histidine-isoleucine-, somatostatin-, neuropeptide Y-, calcitonin gene-related peptide-, substance P-, and galanin-immunoreactive nerves. Neuropeptide Y immunoreactivity was found in 38% of submucosal plexus neurons, within the same neuronal elements as vasoactive intestinal polypeptide immunoreactivity (39% of submucosal plexus neurons) and peptide histidine-isoleucine immunoreactivity. A small population (1% of submucosal plexus neurons) containing vasoactive intestinal polypeptide- and peptide histide isoleucine-like immunoreactivity without NPY-like immunoreactivity was also observed. A significant population of fibers containing vasoactive intestinal polypeptide and galanin immunoreactivity were observed in the mucosa and submucosa, although no cell bodies were detected which contained both neuropeptides. Galanin-like immunoreactivity was seen in a small (2% of submucosal plexus neurons) population, not co-localized with any of the other neuropeptides examined. All somatostatin-immunoreactive neuronal elements (18% of submucosal plexus neurons) contained calcitonin gene-related peptide immunoreactivity, just over half of which also contained substance P immunoreactivity. An additional 25% of submucosal plexus neurons contained calcitonin gene-related peptide- without somatostatin-like immunoreactivity and 28% of submucosal plexus neurons contained substance P without somatostatin-like immunoreactivity. Some degree of co-localization was seen between calcitonin gene-related peptide- and substance P-like immunoreactivity, however, this could not be directly quantified.(ABSTRACT TRUNCATED AT 250 WORDS)