Chemical degeneration of intestinal nerves

In 15 dogs, cobalt chloride solutions were infused close intra-arterially to perfuse a short segment of the jejunum. In an additional four dogs, the jejunum was perfused with the aqueous vehicle (perfusion control). All animals were killed after 1 mo and tissue samples from cobalt-treated and from nonperfused intestine (tissue comparison control) were obtained for electron microscopic and immunohistochemical studies. Segments infused with 0.25 g/dl cobalt solution showed minimal changes; the most striking feature was an increase of vasoactive intestinal polypeptide (VIP)- and substance P-containing neurosecretory granules. Cobalt chloride at higher concentrations (0.75-1.5 g/dl) induced degeneration of ganglion cells and axons in both the myenteric and submucosal plexi. In contrast, the smooth muscle and the mucosal cells of the cobalt-perfused intestine showed no histological abnormalities. Immunohistochemical staining of tissues treated with 0.75-1.5 g/dl cobalt solutions revealed absence of substance P, Met-enkephalin, and VIP immunoreactivity in all section studied; control segments showed the presence of all three peptides. Cobalt chloride in concentrations of 0.75-1.5 g/dl causes degeneration of intestinal intramural nerves and provides an experimental model suitable for studying the role of these nerves in small intestinal function.