Regulation of corpus luteum function in the pouched mouse, Saccostomus campestris

Abstract

Regulation of corpus luteum function was studied in pouched mice, housed under controlled conditions (14L: 10D), (22 ± 2°C). Prolactin in daily doses of 32 IU promoted luteal and uterine development and markedly increased plasma levels of progesterone in females exhibiting estrous cycles. Negligible levels of progesterone in prolactin-treated ovariectomized females ruled out the possibility of a significant nonovarian source of progesterone. Domperidone (a dopamine antagonist) induced pseudopregnancy in cycling females, with a marked increase of peripheral progesterone levels. Pseudopregnancy was also induced by artificial vaginal stimulation of cycling females according to a multiple intromission-multiple ejaculation pattern or a shorter, more concentrated stimulation pattern. The latter treatment, however, resulted in a much weaker histological response of the corpora lutea and uterine horns, although plasma levels of progesterone were similar in the two treatment groups. Recently mated females given domperidone daily did not have progesterone levels above those of mated females treated with vehicle only (both groups pregnant). Bromocriptine (a dopamine agonist) prevented newly mated females from becoming pregnant and interrupted pregnancy when given from Day 6 onward. The progesterone level in these females was lowered. A GnRH-antagonist given to ovariectomized females significantly suppressed LH levels, but intact females given artificial vaginal stimulation and treated with an GnRH antagonist became pseudopregnant. These findings indicate that, in the pouched mouse, as in many other rodent species, pseudopregnancy and progesterone production are dependent on prolactin and not on LH.