DISTRIBUTION OF THE NPY RECEPTOR SUBTYPE Y1 WITHIN HUMAN COLON - EVIDENCE FOR NPY TARGETING A SUBPOPULATION OF NITRERGIC NEURONS

Neuropeptide Y is a neurotransmitter in both the central nervous syste m and the enteric nervous system. Neuropeptide Y receptors have been d emonstrated by in situ hybridization and ligand binding techniques to be present in both of these systems. In this study we report on the di stribution of the Y1 isoform of the neuropeptide Y receptor (YY1) in h uman colon using an antibody raised against the Y1 receptor. This meth od permits greater resolution in determining the distribution of the r eceptor and provides the opportunity to study neurotransmitter markers in relationship to the Y1 receptor. Y1 receptor immunoreactivity was localized within ganglionic neurons and axons of the myenteric and sub mucosal nerve networks, axons within the muscularis mucosae, longitudi nal and circular smooth muscle layers, sympathetic nerve fibers around blood vessels and within scattered cells in the mucosa and basal cell s of the crypts. Neuropeptide Y/Y1 double staining showed that the pep tide and its Y1 receptor subtype were often colocalized within ganglio n cells of Henle's plexus in the submucosa. Thus, Y1 may act as an aut oreceptor within the colonic gut wall. Nitric oxide synthase was found within most neurons of the myenteric plexus which displayed Y1-recept or immunoreactivity but this correlation was not seen in the submucosa . Instead, the colocalization of nitric oxide synthase and Y1-immunore activy was extremely low. These results indicate a striking difference in the Y1 Neuropeptide Y activation of nitrergic mechanisms within th e myenteric and submucosal nerve networks. (C) 1997 Elsevier Science B .V.