Recently, vasoactive intestinal polypeptide (VIP) has been localized in nerve fibers in the
human female genital tract. In the present investigation, the effect and concentration of VIP
was studied in uterine tissue from pregnant and nonpregnant women, and the plasma
concentration of VIP was measured in relationship to diurnal rhythm, intake of food,
menstrual cycle, pregnancy, labor, age, and sexual arousal. In vitro VIP inhibited the
contractions of the nonpregnant but not of the pregnant uterus. The median concentration of …