Mucosa of the guinea pig gastric corpus is innervated by myenteric neurones with specific neurochemical coding and projection preferences

The present study identified and characterised myenteric neurones involved in the innervation of the gastric mucosa. We applied retrograde neuronal tr acing methods by using the dye DiI (1,1'-didodecyl-3,3,3',3'-tetramethylind ocarbocyanine perchlorat) in combination with the immunohistochemical demon stration of choline acetyltransferase (ChAT), enkephalin (ENK), neuropeptid e Y (NPY), nitric oxide synthase (NOS), substance P (SP), and vasoactive in testinal peptide (VIP). This method showed distinct neurochemical coding of DiI-labelled neurones with projections to the mucosa (mucosa neurones): Ch AT/- (indicating the presence of ChAT only, 32%), ChAT/NPY/+/-VIP (22%), NO S/NPY/+/-VIP (19%), ChAT/SP/+/-ENK (12%), NOS/- (indicating the presence of NOS only, 8%), or ChAT/ENK (4.6%). DiI-labelled mucosa neurones did not co ntain calretinin, serotonin, or somatostatin. All ChAT populations had prim arily ascending projections, whereas the NOS populations had mainly descend ing projections. Both were further classified as longitudinally and circumf erentially projecting neurones, the latter having projection preferences to wards the lesser or greater curvature. All subpopulations exhibited project ion preferences. Nitrergic projections primarily arose from cell bodies loc ated at the lesser curvature. ChAT/- projections, which dominated the choli nergic pathway, mainly arose from cell bodies located at the greater curvat ure. The other major cholinergic pathway with the code ChAT/NPY/+/-VIP cons isted of neurones located mainly at the lesser curvature. The results sugge st specific coding of gastric myenteric neurones with projections to the mu cosa. Polarised projections consisted of ascending cholinergic and descendi ng nitrergic neurones; the additional presence of NPY/VIP was a prominent f eature in both pathways. Chemical coding, polarity, and projection preferen ces of enteric pathways to the gastric mucosa are remarkably different from those of other regions in the gut. (C) 1999 Wiley-Liss, Inc.