Interaction of estrogen and histamine during ovum implantation in the rat

The relationship between estrogen and histamine in the initiation of ovum implantation in the rat was studied. Histamine was found to augment the implantation response to suboptimal doses of estradiol in the ovariectomized pregnant rat maintained with Depo-Provera. The effect of histamine was found to involve both H1- and H2-receptors and to be inhibited by treatment with a combination of mepyramine and metiamide. Treatment with this combination of histamine antagonists during early pregnancy in the intact rat did not modify blastocyst attachment. It was concluded that the effect of histamine on the implantation response to exogenous estradiol was due to increased uterine blood flow and/or estrogen uptake but that such histamine-mediated effects were not essential for blastocyst attachment during normal pregnancy.