ELSEVIER Journal of the Autonomic Nervous System 52 (1995) 225-236 Journal of the Autonomic Nervous System Co-existence of nitrergic, peptidergic and acetylcholine esterase-positive nerves in the pig lower urinary tract Katarina Persson a Per Aim b, * Kjell Johansson c, Bengt Larsson a, Karl-Erik Andersson a a Department of Clinical Pharmacology, University of Lund, S-221 85 Lund, Sweden b Department of Pathology, University of Lund, S-221 85 Lund, Sweden c Department of Zoology, University of Lund, S-221 85 Lund, Sweden Received 9 February 1994; revision received and accepted 24 August 1994 Abstract The distribution of NO synthase (NOS) immunoreactive nerves and the possible co-existence with other neurotransmitters were investigated in the pig lower urinary tract. NOS immunoreactive nerves were found in the muscle layer, in the lamina propria and around blood vessels. The density 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 nerves. The number of adrenergic nerves in the trigone and urethra was moderate to rich, whereas only very few adrenergic nerves were demonstrated in the detrusor. A low to moderate number of nerve fibres containing neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) were observed in the trigone and urethra, while very few were found in the detrusor. A small number of nerves, confined to the trigone and urethra, were stained for calcitonin-gene-related peptide, somatostatin and leu-enkephalin. Nerve fibres exhibiting immunoreactivity to bombesin/gastrin releasing peptide, gastrin/cholecystokinin, substance P or neurokinin A were virtually absent. Co-localization studies revealed that some NOS-immunoreactive nerves also stained for NPY, VIP or ACHE. The present study shows that nitrergic nerves are present in the pig lower urinary tract in a density lower than the cholinergic, but higher than 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 directly and by interaction with other transmitters. Keywords: Urinary tract; Nitric oxide synthase; Autonomic nervous system; Neuropeptide; (Pig) I. Introduction In the urinary tract, much interest has been focused on peptides as potential mediators of * Corresponding author. Tel.: (46-46) 173-405; Fax: (46-46) 143-307. non-adrenergic, non-cholinergic (NANC) effects, and both intraneuronal storage and functional responses can be demonstrated (e.g., Refs. 3 and 30). The purine ATP seems to be the main non- cholinergic excitatory transmitter in the detrusor [3,10]. Despite extensive research, no candidate for the inhibitory NANC transmitter involved in 0165-1838/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0165-1838(94)00160-X