I believe that it depends on the tissue you are studying and on what properties of that tissue your are studying.  For example, we study skeletal muscle in mice. For one physiological property of muscle, the effect of estradiol removal/addition is on the order of minutes, maybe tens of minutes. For another physiological property of muscle, the effect of estradiol is mediated genomically so the effect is much slower in nature, e.g., days. However, for most of our studies, we wait at least two weeks after ovariectomy and usually wait 3-4 weeks to be on the safe side. We have never really tried to rigorously examine the effect(s) of estradiol on muscle as a function of time after ovariectomy.

Many researchers use uterine weights as indicators of estradiol presence/absence. The weights can change rapidly with removal or addition of estradiol.

In previous studies, Estradiol levels 40 day after ovariectomy is significantly reduced compared to the first week.

It seems, reducing the effect depends on the tissue your study.

Sexual behavior disappears at least 1 week after ovx in rats and mice. However, odor of the females still attracts males 1 or 2 weeks after ovx. Thus, when collecting some samples without estrogen influence, we would take 3 or more weeks after ovx.

Also you should remember that fat accumulate estrogen, so if you have very heavy female you should wait longer.

Hi Cinthia,

3 weeks should be already ok to get rid of estrogen influence, but to be on the safe side we always wait 6 weeks, especially to be sure to get rid of estradiol stored in the animal's fat. Also note that there could be a local estradiol synthesis in the brain, depending on which tissue you want to analyse.

Two papers that you could reference/read : Brock and Bakker, Endocrinology 2013; Konkle and McCarthy, Endocrinology 2011. 

Thanks to all. I am studying the effects of ovariectomy on the brain, specifically iba the suprachiasmatic nucleus. In my previous results I have observed that there is a shortening of the period of locomotor activity after 45 days of surgery.

At least two weeks as per EPA and OECD guidelines for

Uterotrophic Assay : OPPTS 890.1600

My experience tells me that after a ovariectomization in rats, the estrogenic decrease decreases after the first week, its total effect is estimated around 4 weeks after the operation in animal