COEXISTENCE OF NITRERGIC, PEPTIDERGIC AND ACETYLCHOLINE ESTERASE-POSITIVE NERVES IN THE PIG LOWER URINARY-TRACT

The distribution of NO synthase (NOS) immunoreactive nerves and the po ssible co-existence with other neurotransmitters were investigated in the pig lower urinary tract. NOS immunoreactive nerves were found in t he muscle layer, in the lamina propria and around blood vessels. The d ensity of NOS immunoreactive nerves was more prominent in the trigone and urethra than in the detrusor. All parts of the lower urinary tract were supplied by numerous acetylcholine esterase (AChE) positive nerv es. The number of adrenergic nerves in the trigone and urethra was mod erate to rich, whereas only very few adrenergic nerves were demonstrat ed in the detrusor. A low to moderate number of nerve fibres containin g neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) wer e observed in the trigone and urethra, while very few were found in th e detrusor. A small number of nerves, confined to the trigone and uret hra, were stained for calcitonin-gene-related peptide, somatostatin an d leu-enkephalin. Nerve fibres exhibiting immunoreactivity to bombesin /gastrin releasing peptide, gastrin/cholecystokinin, substance P or ne urokinin A were virtually absent. Co-localization studies revealed tha t some NOS-immunoreactive nerves also stained for NPY, VIP or AChE. Th e present study shows that nitrergic nerves are present in the pig low er urinary tract in a density lower than the cholinergic, but higher t han any of the studied peptidergic nerves. Coinciding localization of NOS-positive nerves with nerves expressing AChE, VIP and NPY suggests that NO may have a role as a messenger in the lower urinary tract dire ctly and by interaction with other transmitters.