NITRIC-OXIDE SYNTHASE-CONTAINING NERVE ELEMENTS IN THE PYLORUS OF THECAT

Combined nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH -d) histochemistry, nitric oxide synthase (NOS) and vasoactive intesti nal polypeptide (VIP) immunocytochemistry were used to study the distr ibution of NOS- and VIP-containing nerve elements in the feline pyloru s. A large number of stained multipolar neurons was found in the myent eric plexus. However, some NADPH-d and NOS positive neurons were also observed in the submucous plexus and in the internal part of muscular layer. A few stained perikarya were found in the tunica mucosa, in a v ery close situation to the blood vessels. A large number of thin varic ose fibres, with intense reaction for all markers were seen around or in close contact with the unstained perikarya to the blood vessels and some of them around the pyloric glands. The density of NOS and NADPH- d positive nerve elements was much higher than that of VIP-immunoreact ive (IR) nerve elements. Our results suggest that nitric oxide (NO) mi ght act as a regulatory neurotransmitter of the pyloric sphincter, blo od flow and secretion in this region.