The relationships of nicotinamide adenine dinucleotide phosphate-d to nitric oxide synthase, vasoactive intestinal polypeptide, galanin and pituitaryadenylate activating polypeptide in pigeon gut neurons

The distribution of nicotinamide adenine dinucleotide phosphate (NADPH)-d n eurons and their relationship with nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), pituitary adenylate activating polypeptide (P ACAP) and galanin (Gal) were examined in the gastrointestinal (GI) tract of the pigeon Columbia livia. NADPH-d-histochemistry, indirect immunofluoresc ence and confocal analysis were applied to cryosections. Western blot analy sis was also applied on pigeon gut. NADPH-d neurons were found throughout t he pigeon GI tract and they were evident in the myenteric, circular muscle and submucous plexuses. Positive varicose nerve fibres were also distribute d within the longitudinal muscle layers and in the lamina propria of the mu cosa. The stomach was the segment richest in positivities. The copresence V IP/Gal/NOS as well as PACAP/VIP were revealed in some NADPH-d-neurons. We s uppose that the nitrergic nerve population of the pigeon GI tract belong to the muscle motility regulation as an inhibitory descending nerve pathway. Moreover the presence of VIP, Gal and PACAP in some NADPH-d-containing neur ons enhances the inhibitory actions of these neurotransmitters whereas PACA P and Gal role is actually unknown. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.