Effect of mepyramine, a histamine H1-, and burimamide, a histamine H2-receptor antagonist, on ovum implantation in the rat.

Systemic administration to rats of a combination of mepyramine, a histamine H1-, and burimamide, a histamine H2-receptor antagonist, over a period which included the time of implantation (late Day 5 to early Night 5), increased the number of blastocysts recovered from the uterus and reduced the number and intensity of Pontamine Sky Blue (PSB) sites obtained at autopsy on Night 5. Histological examination of the PSB sites taken on Night 5 from animals receiving the histamine antagonists revealed that the stromal oedema, which is characteristic of the attachment phase of pregnancy, had been inhibited.