[Use of gonadoliberin (GnRH) or analogs in veterinary medicine. Pharmacologic and therapeutic evaluation in cattle].
The author reports here the pharmacological and therapeutic effects of GnRH or analogues in cattle, species to which claims are both the most clearly identified and diverse. A single challenge of GnRH (doses between 100 and 1,500 micrograms) results in an enhanced and simultaneous release of both LH and FSH in a log dose-response manner. Clearance of GnRH injected intramuscularly is parallel to the LH and FSH release patterns ie maximum concentrations in 15-30 minutes and return back to basal levels in 6 hours approximately. This gonadotropin release in turns stimulates the release of gonadal steroids. The magnitude of the gonadotropins release in response to GnRH is dependent upon both the gonadal and adrenal steroids. Advantage of these properties has been taken in the bovine females to treat those that are 1) in true anoestrus after calving, 2) so-called "Repeat-Breeders", 3) so-called subfertile and treated then at the time of insemination, 4) with an ovarian cyst syndrome and 5) to improve the superovulation treatments. The most difficult problem to solve remains that of inducing cyclicity during the post-partum period especially in suckled beef cows. Several attempts have been made, injecting GnRH with intermittent, pulsatile or even infusion regimes. Results are still inconsistent. The most striking result is that observed in Repeat Breeders when GnRH is injected at mid luteal phase prior to insemination. Such a regime results in an enhanced conception rate compared to controls and it has been shown that it improves dramatically both the recovery rate and the rate of good quality embryos when experimentally collected 11 days after artificial insemination. Although encouraging results have been recorded, quite a few points are still controversial or unclear. More work is needed to help in improving the efficacy of GnRH therapy. Emphasis should be given on slow release devices.
D000818:Animals; D002417:Cattle / Q000502:physiology*; D004971:Estrus / Q000187:drug effects*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007986:Luteinizing Hormone / Q000378:metabolism; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D011247:Pregnancy
D010906:Pituitary Hormone-Releasing Hormones; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone
Le recours à la gonadolibérine (GnRH) ou analogues en médecine vétérinaire. Analyse pharmacologique et thérapeutique chez les bovins.