Distribution, pathways and reactions to drug treatment of nerves with neuropeptide Y- and pancreatic polypeptide-like immunoreactivity in the guinea-pig digestive tract.

Pancreatic polypeptide-like immunoreactivity (PPLI) has been localized in nerves of the guinea-pig stomach and intestine with the use of antibodies raised against avian, bovine and human pancreatic polypeptide (PP), the C-terminal hexapeptide of mammalian PP, and against the related peptide, NPY. Each of the antibodies revealed the same population of neurones. Reactive cell bodies were found in both myenteric (5% of all neurones) and submucous ganglia (26% of all neurones) of the small intestine, and varicose processes were observed in the myenteric plexus, circular muscle, mucosa and around arterioles. The nerves were unaffected by bilateral subdiaphragmatic truncal vagotomy, but the staining of the periarterial nerves disappeared after treatment of animals with reserpine or 6-hydroxydopamine and was also absent after mesenteric nerves had been cut and allowed to degenerate. Vascular nerves showing immunoreactivity for dopamine beta-hydroxylase and PPLI had the same distribution. It is concluded that PPLI is located in periarterial noradrenergic nerves. However, other noradrenergic nerves in the intestine do not show PPLI, and PPLI also occurs in nerves that are not noradrenergic. Analysis of changes in the distribution of terminals after microsurgical lesions of pathways in the small intestine showed that processes of myenteric PP-nerve cells provide terminals in the underlying circular muscle and in myenteric ganglia up to about 2 mm more anal. Submucous PP-cell bodies provide terminals to the mucosa.