The role of the uterus and cervix in systemic oxytocin-PGE2 facilitated lordosis behavior

The effect of ovariectomy, hysterectomy, and cerviectomy on systemic oxytocin-PGE2 induced facilitation of lordosis behavior was examined in estrogen and progesterone treated rats. Females were injected with 0.25 micrograms estradiol benzoate for 3 days, followed by 500 micrograms progesterone on day 4, 4 hr prior to behavioral testing. Ten minutes before behavioral testing with a male, females were injected systemically with either oxytocin (2.1, 4.2, or 8.4 micrograms); PGE2 (0.05, 0.10, or 0.20 micrograms); concomitant administration of both oxytocin and PGE2; or physiological saline. Oxytocin (2.1 micrograms) or PGE2 (0.05 micrograms) significantly increased lordosis behavior in ovariectomized females; however, neither had any facilitatory effect in hysterectomized animals. Facilitated lordosis behavior was only reinstated in hysterectomized females that received concomitant administration of 2.1 micrograms oxytocin plus 0.05 micrograms PGE2. This latter dose also resulted in a further potentiation of lordosis behavior in ovariectomized animals, compared to 2.1 micrograms oxytocin or 0.05 micrograms PGE2 alone. Concomitant administration of oxytocin and PGE2 at all doses had no facilitatory effect on lordosis behavior in cerviectomized animals. These results suggest that the uterus and the cervix may be important components of a peripheral mechanism by which systemic oxytocin and/or PGE2 induce facilitated lordosis behavior in female rats.