Nitric oxide-containing neurons in the bovine gut, with special reference to their relationship with VIP and galanin

The presence and distribution of nicotinamide dinucleotide phosphate diapho rase (NADPH-d)-containing neurons have been studied by means of NADPH-d his tochemistry in different regions of the adult cow gut, from the esophagus t o the rectum. NADPH-d and nitric oxide synthase (NOS) were constantly recognized to be co localized in the same neuron. The colocalization of vasoactive intestinal p olypeptide (VIP) and galanin in such nitrergic neurons was also studied by means of combined histochemical and immunofluorescence techniques. NADPH-d- positive neurons were present along the myenteric plexus of the entire gut, and in the submucous plexus from the abomasum to the rectum. Notably, they formed two types of nerve networks in the submucous connective tissue of t he jejunum-ileum. NADPH-d-positive innervation of the muscle layers occurre d throughout the tract, and sometimes a clear correspondence was noted betw een the number of reactive fibres and the thickness of the muscle. Nitrergi c fibres also occurred in the mucosa and often were in relation to glands a nd blood vessels. The nitrergic neurons varied in size, shape, and intensit y of staining, and often their terminals were seen to surround unstained pe rikarya. Various types of neurons were recognized on the basis of their che mical content; one of them contained galanin, VIP and NOS simultaneously. The present results suggest that the nitrergic neurons of the bovine gastro intestinal tract play roles presumably for controlling the motility of the gut and the conduction of interneuronal impulses.