Distribution of nitric oxide synthase containing elements in the feline submandibular gland

Combined nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and nitric oxide synthase (NOS) immunocytochemistry were used to study the distribution of nitric oxide synthesizing elements in the cat submandibular gland. A large number of thin varicose fibres, with intense staining for both markers, were seen around or in close contact with the acini. Some of the stained nerve fibres were associated with intra- and interlobular salivary ducts and blood vessels. All neurones in the submandibular ganglia showed intense staining for both NADPH-d and NOS. The epithelial layer of the salivary ductal branches and the endothelial lining of blood vessels were NOS immunonegative but NADPH-d positive. Our results suggest that NO might act as a neurotransmitter in the regulation of blood flow and secretion in the submandibular salivary gland.