Replacement of progesterone restores the nocturnal surge of prolactin following suppression with a gonadotropin-releasing hormone agonist during early pregnancy in the rat.
Continuous administration of a GnRH agonist (GnRH-Ag) at a dose of 5 micrograms/day, commencing on day 7 of pregnancy resulted in the suppression of daily nocturnal surges of prolactin (PRL) on day 8, and serum progesterone (P4) levels with subsequent termination of pregnancy. Replacement with dydrogesterone, a synthetic analog of P4 at a dose of 4 mg/day s.c. restored the magnitude of nocturnal PRL surges. These data suggest that GnRH-Ag may act either at the level of the brain to suppress the nocturnal PRL surge, resulting in a fall in serum P4 levels or at the level of the corpus luteum itself or at both sites simultaneously to terminate pregnancy.
Joseph
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Department of Physiology, Morehouse School of Medicine, Atlanta, GA 30310-1495.
Sridaran
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D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D004394:Dydrogesterone / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D007263:Infusions, Parenteral; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D011374:Progesterone / Q000097:blood / Q000378:metabolism*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D011388:Prolactin; D004394:Dydrogesterone; C030741:lutrelin acetate