The failure of prolactin to enhance the inhibitory effect of oestradiol-17 beta on LH synthesis and release in ewes.
Groups of 5-6 ovariectomized ewes were treated with oestradiol-17 beta (100 mg implant) and/or bromocriptine (1 mg; 2 X daily) or with vehicle for 30 days during the anoestrous season. Oestradiol increased (P less than 0.05) the priming effect of 2 X 1 micrograms LH-RH on LH release and decreased (P less than 0.001) pituitary LH content, plasma LH levels, the frequency and amplitude of pulsatile LH release and the LH response to LH-RH. Bromocriptine decreased prolactin levels to less than 2.5 ng/ml (P less than 0.001) and increased the LH response to LH-RH (P less than 0.05). There were no significant treatment interactions. It is concluded that prolactin does not enhance the inhibitory effect of oestradiol on LH synthesis and release in the ewe.
D000780:Anestrus; D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D002369:Castration; D003864:Depression, Chemical; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007986:Luteinizing Hormone / Q000096:biosynthesis* / Q000378:metabolism; D011247:Pregnancy; D011388:Prolactin / Q000097:blood*; D012756:Sheep
D001971:Bromocriptine; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone