MORPHOLOGICAL ANALYSIS OF VAGAL INPUT TO GASTRIN-RELEASING PEPTIDE AND VASOACTIVE-INTESTINAL-PEPTIDE CONTAINING NEURONS IN THE RAT GLANDULAR STOMACH

Vagal preganglionic efferents to the rat stomach were labeled anterogr adely by injecting the fluorescent carbocyanine dye DiA into the dorsa l motor nucleus in vivo. Enteric neurons were labeled in tote by intra peritoneal administration of Fluorogold, and neurochemically character ized by simultaneous single- and double-label immunocytochemistry. Sin gle peptide immunocytochemistry revealed that in all three major areas of the stomach, about one-third of all gastrin-releasing peptide immu noreactive (GRP-IR) neurons in the myenteric plexus, received vagal co ntacts. Because the proportion of GRP-IR neurons was 32% in the fundus , 23% in the corpus, and only 8% in the antrum, the absolute number of vagally contacted GRP-IR neurons per cm(2) was also different. Double -label immunocytochemistry revealed colocalization of vasoactive intes tinal peptide immunoreactivity (VIP-IR) in 45%, and of enkephalin immu noreactivity (ENK-IR) in about 30%, of the GRP-IR myenteric neurons. A subpopulation of myenteric neurons colocalized GRP-IR and VIP-IR and projects almost exclusively to the gastrin cell-rich basal mucosa of t he antrum and the oxyntic mucosa of the corpus. Another subpopulation containing GRP-IR, but not VIP-IR, projects mainly to the myenteric pl exus itself and the external muscle layers, particularly the longitudi nal muscle. A third group of neurons containing VIP-IR but not GRP-IR projects heavily to the circular muscle layer, the muscularis mucosae, and to other myenteric neurons. Vagal input to these three subpopulat ions seems not to be selective, in that an equal proportion of about 2 0 to 30% of each group was vagally contacted. Vagal inputs to these ne urochemically and topographically distinct enteric neurons provide the basis for the physiological vagal control of gastrin release, gastric acid secretion, and gastric motility. (C) 1996 Wiley-Liss, Inc.