Nerve fibers in the gut and pancreas of the rat displaying neuropeptide-Y immunoreactivity. Intrinsic and extrinsic origin.

Immunoreactive neuropeptide Y (NPY) was demonstrated in neuronal elements in the gut and pancreas of the rat. Immunoreactive endocrine cells could not be detected. The occurrence of NPY-containing nerve-cell bodies in the submucosal and myenteric ganglia indicates an intrinsic origin of the NPY fibers. However, an additional extrinsic supply of NPY fibers is suggested by the finding that abdominal sympathectomy caused the disappearance of some NPY fibers, notably those around blood vessels. The distribution of NPY fibers in all layers of the gut wall suggests multiple functions of NPY, including a role in the regulation of intramural neuronal activities, smooth muscle tone, and local blood flow.