IMMUNOCYTOCHEMICAL LOCALIZATION OF THE NPY PYY Y1 RECEPTOR IN ENTERICNEURONS, ENDOTHELIAL-CELLS, AND ENDOCRINE-LIKE CELLS OF THE RAT INTESTINAL-TRACT/

Neuropeptide Y (NPY) and peptide YY (PYY) are structurally related pep tides that are considered to mediate inhibitory actions on gastrointes tinal motility, secretion, and blood flow. Several receptor subtypes f or these peptides have been identified and the Y1, Y2, YL4/PP1, Y5, an d Y5/PP2/Y2b receptors have been cloned. In this article we report the immunocytochemical localization of the Y1 receptor to myenteric and s ubmucosal nerve cell bodies, endothelial cells, and scattered endocrin e-like cells of rat intestinal tract. Moreover, double immunofluoresce nce demonstrates that subpopulations of the Y1 receptor-positive nerve cell bodies are immunopositive for NPY, vasoactive intestinal polypep tide, and nitric oxide synthase. In part, such co-localizations were m ade possible by use of peroxidase-mediated deposition of tyramide, whi ch permitted use of antisera derived from the same species. Our observ ations suggest the existence of multiple neuronal, endothelial, and en docrine target sites for NPY and PW and that some of the actions of th ese regulatory peptides can be mediated by vasoactive intestinal pepti de and nitric oxide synthase.