NADPH-DIAPHORASE AND NANC RELAXATIONS ARE CORRELATED IN THE SHEEP URINARY-TRACT

The present investigation was performed with the purpose of revealing by histochemical examination of NADPH-diaphorase activity and electrical field stimulation (EFS) of isolated preparations in vitro, whether a nitrergic innervation is present in the lower urinary tract of the sheep. NADPH diaphorase positive fibers were found in the trigone and urethra, but not in detrusor and ureter. EFS elicited L-nitroarginine-sensitive relaxations of precontracted preparations from the trigone and urethra while it did not relax detrusor and ureteral preparations. The present results show a direct regional correlation between the NADPH-diaphorase activity and EFS-induced relaxations, and suggest the presence of an inhibitory nitrergic innervation, which might be of importance for relaxation of the bladder neck and urethra during voiding.