Relaxation of human female genital sphincters by the neuropeptide vasoactive intestinal polypeptide

Vasoactive intestinal polypeptide (VIP), a recently recognized neuropeptide with a putative transmitter function, has been demonstrated in nerves in the female genital tract. The highest density is in the smooth, muscle of the isthmus of the fallopian tubes and of the uterine cervix. The motor effect of VIP has been tested in vitro of smooth muscle from the isthmus and the uterine cervix. Both preparations responded to VIP with a concentration-dependent reduction in motor activity.