Distribution of NADPH-diaphorase-positive nerves supplying the human urinary bladder.

Nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry was used as a marker for neuronal nitric oxide synthase in human bladder tissue. A plexus of NADPHd-containing nerve fibres was observed in bladder biopsies taken from both the lateral wall and trigone regions. Varicose terminals were present in smooth muscle bundles of the detrusor and trigone, and more commonly within the submucosal layer. Reactive fibres were seen running immediately beneath and along the urothelium, and additional nerves formed perivascular plexi around some blood vessels. Fewer positive nerve processes were observed in the trigone region in comparison to the bladder wall. NADPHd-reactive neuronal perikarya were present within intramural ganglia, some of which were in close proximity to NADPHd-stained varicosities. The results indicate that nitric oxide may be involved in the regulation of bladder function in humans.