SOMATOSTATIN IS PRESENT IN A SUBPOPULATION OF NORADRENERGIC NERVE-FIBERS SUPPLYING THE INTESTINE

Somatostatin and dopamine .beta.-hydroxylase have been localized in the celiaco-mesenteric ganglia, in mesenteric nerves and in the wall of the guinea-pig small intestine. Nerve lesions were used to determine the sources of the nerves. Nerve cell bodies in the celiaco-mesenteric ganglia with immunoreactivity for both somatostatin and dopamine .beta.-hydroxylase project to the intestine via the mesenteric nerves. Most of their terminals are in the submucous ganglia, where they make up the full complement of noradrenergic terminals, and in the mucosa where other noradrenergic terminals, not containing somatostatin immunoreactivity, are also present. The small number of noradrenergic fibers present in the tertiary component of the myenteric plexus and in the circular muscle all show immunoreactivity for somatostatin. The noradrenergic fibers supplying the mesenteric and intestinal blood vessels and those ramifying in the myenteric ganglia do not contain somatostatin. The numerous somatostatin-immunoreactive nerves in the enteric plexuses that do not contain dopamine .beta.-hydroxylase come from enteric nerve cell bodies. Post-ganglionic sympathetic noradrenergic neurons apparently are chemically coded according to the target tissue they supply and suggest that neurons that were hitherto thought to be neurochemically equivalent, but which serve different functions, are in fact chemically distinct.