Vasoactive intestinal polypeptide influence on lower urinary tract smooth muscle from human and pig

The influence of vasoactive intestinal polypeptide on detrusor, trigone, bladder neck and urethral smooth muscle from human and pig was investigated in vitro. Vasoactive intestinal polypeptide reduced the tension and amplitude of the spontaneous contractions of strips from all regions studied. Human detrusor and pig trigone, bladder neck and urethral strips were more sensitive to vasoactive intestinal polypeptide than pig detrusor. The response was reversible, reproducible and dose-dependent from 10(-9) to 10(-6) mol. per liter. The time to onset of the response was within 1/2 minute and the time to maximal relaxation was 2 to 10 minutes. The response was not affected by selective nerve poisoning with tetrodotoxin, beta-adrenergic blockade with propanolol or prostaglandin synthesis blockade with ketoprofen. Vasoactive intestinal polypeptide did not prevent prostaglandin E2 activity on the musculature. Contractions evoked by transmural electric field stimulation or pharmacologically with carbachol, noradrenaline, substance P and prostaglandin F2 alpha were equally reduced by VIP 10(-7) mol. per liter.