Ovarian control of prolactin secretion during late pregnancy in the rat

The involvement of the ovaries during late pregnancy in the rat upon serum prolactin was investigated. Ovariectomy on day 17 or day 21 of pregnancy prevented the dramatic rise of prolactin found in sham-ovariectomized animals between days 21 and 23 of pregnancy. While animals ovariectomized on day 17 of pregnancy failed to carry viable fetuses beyond day 19 of pregnancy, rats ovariectomized on day 21 of pregnancy had viable pups in utero on day 23 of pregnancy. These data suggest that the rise in serum prolactin during late pregnancy is stimulated by ovarian factors.