Modulation of uterine contractility and peristalsis by oxytocin in estrogen-primed non-pregnant swine uteri.

Oxytocin is one of the most potent uterotonic agents and is known to fluctuate throughout the menstrual cycle, showing an increase during sexual stimulation and arousal, with a peak during orgasm in women. To date, limited data are available on the effects of oxytocin on the regulation of uterine contractility and transport mechanisms in human reproduction. The goal of this study was to evaluate the effects of oxytocin on uterine contractility and peristalsis in estrogen-primed non-pregnant uteri. In an extracorporeal perfusion model of the swine uterus the effect of dynamic changes in uterine contractility and peristalsis in response to oxytocin and estrogen administration was observed. Spontaneous uterine contractility and oxytocin-induced uterine contractility and peristalsis with and without estrogen perfusion were assessed using an intrauterine double-chip microcatheter. Spontaneous peristalsis and oxytocin induced contraction waves without estrogen perfusion resulted in a slightly higher intrauterine pressure in the isthmus uteri in comparison with the corpus uteri, while the peristaltic waves were seen to start mostly in the corpus uteri, moving in the direction of the cervix. While after estrogen perfusion oxytocin produced a significant increase in intrauterine pressure in the isthmus uteri compared to the corpus uteri, and 80% of the peristaltic waves started in the isthmus uteri, moving in the direction of the corpus uteri. This observation strengthens the view that oxytocin is able to support directed transport mechanism in the female genital tract only in the presence of estrogens. The biological role of oxytocin increase during sexual stimulation and arousal with a peak during orgasm for the mechanisms of reproduction may be to stimulate directed uterine transport mechanisms in the presence of estrogens.