title: Plasma LH concentrations in the ewe in response to repeated injections of low doses of gonadotrophin releasing hormone during the follicular phase of the oestrous cycle.
abstract: Oestrus was synchronized in 15 naturally cyclic ewes by the administration of a prostaglandin F2 alpha analogue. Groups of five ewes were then treated i.v. with either small doses of gonadotrophin releasing hormone (GnRH; 125 or 250 ng/injection) or saline, at 2-h intervals from day 14 of the subsequent cycle until 24 h after the onset of oestrus. Treatment with GnRH induced episodic LH release which continued until the onset of a preovulatory LH surge. Mean plasma LH concentrations over this period were significantly (P less than 0.001) higher in animals receiving 250 ng GnRH (2.44 +/- 0.11 microgram/1) than in those receiving either 125 ng GnRH (1.17 +/- 0.06 microgram/1) or saline (1.14 +/- 0.05 microgram/1). However, GnRH treatment did not influence the timing of oestrus or mean ovulation rates.
mesh_terms: D000818:Animals; D004971:Estrus / Q000187:drug effects; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood*; D010060:Ovulation / Q000187:drug effects; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D011247:Pregnancy; D011359:Proestrus; D011374:Progesterone / Q000097:blood; D012756:Sheep
chemical_list: D010906:Pituitary Hormone-Releasing Hormones; D011374:Progesterone; D007986:Luteinizing Hormone