Induction of ovulation in seasonally anoestrous ewes by continuous infusion of low doses of Gn-RH.
Two groups of 12 seasonally anoestrous ewes were infused with Gn-RH at the rate of 125 or 250 ng/h for 48 h. Four control ewes were infused with the saline vehicle alone. Mean LH concentrations increased significantly in response to Gn-RH infusion and were significantly higher (P less than 0.05) in ewes receiving 250 ng Gn-RH/h. LH concentrations remained unchanged in the control ewes. Oestrus was detected in 22/24 Gn-RH-treated ewes and occurred at a mean time of 37.0 +/- 1.2 h after the start of infusion. Ovulation occurred in all but one of the 24 Gn-RH-treated ewes with mean ovulation rates of 1.27 +/- 0.14 (125 ng-Gn-RH/h) and 1.75 +/- 0.22 (250 ng Gn-RH/h). These results demonstrate that a sustained elevation in mean circulating concentrations of LH induced by continuous administration of Gn-RH is sufficient to invoke the final phases of follicular development, and thereby ovulation, in the seasonally anoestrous ewe.
D000780:Anestrus / Q000187:drug effects*; D000818:Animals; D004971:Estrus / Q000187:drug effects*; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood*; D010062:Ovulation Induction; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012621:Seasons; D012756:Sheep
D010906:Pituitary Hormone-Releasing Hormones; D011374:Progesterone; D007986:Luteinizing Hormone