The ultimobranchial glands of 20 chickens, aged 2-3 months, were investigated for their nicotinamide adenine dinucleotide hydrogen phosphate-diaphorase (NADPH-d) reactivity and the distribution of nitric oxide synthase (NOS), using NADPH-d histochemistry and NOS immunocytochemistry respectively. Formazan, the blue reaction product of NADPH-d, was localised in the neuronal cell bodies and nerve fibres. Most of the cell bodies were found in the parenchyma. Some of them occurred in the wall of the ultimobranchial cysts, and a few in the immediate vicinity of the blood vessels. Labelled nerve fibres mostly travelled with blood vessels, while few of them appeared in the cystic lining. In addition to neuronal profiles, some C cells, cystic lining, and vascular endothelium were also labelled. NOS staining was found in neuron-like cells and fibres that were confirmed as neurons in adjacent sections stained with antibodies against neuron-specific enolase. It was also detected in cystic lining and in some C cells, but not in vascular endothelium. The distribution patterns of NADPH-d and NOS suggest that NO may play a role in the regulation of the secretory activity of and the blood flow through the ultimobranchial glands.

The bursa of Fabricius of 24 chickens, 2-4 weeks old, was investigated to determine the distribution of nicotinamide adenine dinucleotide hydrogen phosphate-diaphorase (NADPH-d) staining and nitric oxide synthase (NOS) antigen, by use of NADPH-d histochemistry and NOS immunohistochemistry, respectively. NADPH-d reaction product was localised in neuronal cell bodies and nerve fibres. The stained cell bodies were predominantly in the different bursal compartments; some occurred in the wall and between the lymphoid follicles, and some in the immediate vicinity of blood vessels. Stained nerve fibres travelled mostly with blood vessels, but many were also observed in the connective tissue of the bursa, independent of blood vessels, and some in contact with the lymphoid follicle and interfollicular epithelium. In addition to neuronal profiles, the interfollicular epithelium of the plicae, and the vascular endothelium were densely stained, and lymphocytes were moderately labelled. NOS immunoreactivity was found in neuron-like cells and fibres which were confirmed to be neuronal in adjacent sections stained with antibodies raised against neuron-specific enolase. It was also detected in interfollicular epithelium and lymphocytes but not in vascular endothelium. The distribution patterns of NADPH-d and NOS suggest that nitric oxide (NO) may play a role in the regulation of the secretory activity of interfollicular epithelium and the blood flow through the bursa.