title: GnRH-antagonist mediated down-regulation of the estrous cycle in marmosets.
abstract: BACKGROUND
  Because of its small size and unproblematic captivity behavior the marmoset monkey is an attractive New World primate model for early developmental questions. However, superovulation protocols used in Old World monkeys and women are not successful in the female marmoset. A novel protocol is needed to utilize these New World monkeys as an efficient animal model for in vitro fertilization experiments or embryo stem cell research.
  
  
  METHODS
  To create such a protocol we first examined the effects of long-term estrous cycle control, secondly, in a dose-finding study, we determined the length of a down-regulation protocol with a gonadotropic releasing hormone (GnRH)-antagonist. Twenty-nine female marmosets were grouped according to the number of estrous cycles, which had been controlled for a period of 12 months in which 88 cycles were monitored. Application of PGF2alpha in the mid-luteal phase led to immediate onset of the follicular phase. The blood progesterone concentration rapidly declined and increased again on day 9-11.
  
  
  RESULTS
  The results show that the controlled ovarian cycle length and progesterone response are not altered by the number of PGF2alpha injections. The rapid decline was similar in all groups, indicating that all animals, independent of the number of controlled cycles, react equally to multiple PGF2alpha injections. To determine the proper dosage for a GnRH-antagonist (Cetrorelix), 12 animals in three groups of four female marmosets were treated with two different dosages and a sham dosage. Cetrorelix was applied in the mid-luteal phase, three times over 2 days. In both Cetrorelix-treated animal groups the early progesterone levels matched those in the controls. In the low-dose treatment group [0.01 mg/100 g body weight (BW)] the expected progesterone rise on day 10 was delayed between 9 and 15 days whereas in the high-dose treatment group (0.1 mg/100 g BW) the progesterone rise was delayed between 21 and 41 days. In the low-dose group the steepness of the slope from day 20 onwards was almost identical to that of the control group. This was reflected in the bioCG levels measured.
  
  
  CONCLUSIONS
  Based on the GnRH-antagonist studies, complete ovarian down-regulation in female marmosets can be achieved by applying a low-dose regimen, and intrinsic gonadotropins would not interfere with an ovarian superstimulation protocol.
authors.affiliation: Institute of Reproductive Medicine of the University, Münster, Germany.
authors.forename: C Marc
authors.initials: CM
authors.lastname: Luetjens
authors.forename: Ramona
authors.initials: R
authors.lastname: Wesselmann
authors.forename: Michael
authors.initials: M
authors.lastname: Kuhlmann
mesh_terms: D000818:Animals; D002144:Callithrix / Q000502:physiology*; D003008:Cloprostenol / Q000494:pharmacology*; D015237:Dinoprost / Q000494:pharmacology*; D030762:Estrous Cycle / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006727:Hormone Antagonists / Q000494:pharmacology; D013997:Time Factors
chemical_list: D006727:Hormone Antagonists; D007987:Gonadotropin-Releasing Hormone; D003008:Cloprostenol; D015237:Dinoprost; C062876:cetrorelix