The aim of the present study was to determine if the estradiol-induced luteinizing hormone (LH) surge is influenced by the constant exposure to TAK-683, an investigational metastin/kisspeptin analog, that had been established to depress the pulsatile gonadotropin-releasing hormone (GnRH) and LH secretion in goats. Ovariectomized goats subcutaneously received TAK-683 (TAK-683 group, n=6) or vehi...

The effects of third ventricular injection of beta-endorphin (beta-EP) on spontaneous, brain stimulation-induced and estrogen-induced LH surges were studied in the adult female rat. It was found that beta-EP blocked the preovulatory surge of LH release and ovulation, while it did not affect LH release in response to LH-RH injection. The site of the beta-EP blockade of ovulation was proved to be...

WEICK, RICHARD F., AND DAVID K. POMERANTZ. M~IMInisrn of ir&don of L,H surgc~ in thu r-hews rrm~&~.v: positiw f~dbrrr~k of estrqprz.2 Am. J. Physiol. 236( II: R102-R106, 1979 or Am. J. Physiol.: RegulatorG Integrative Comp. Physiol. 5( 1): R102-R106, 1979. Exper&nts were desiqed to determine whether the luteinizing hormone (LH) surge induced by estrogen results from a positive feedback effect o...

OBJECTIVE To evaluate the efficacy of earlier oocyte retrieval in IVF patients with a premature LH surge on hCG day. METHODS One hundred forty IVF patients (164 cycles) with premature LH surge on hCG day were included, retrospectively. We divided them into 2 study groups: LH surge with timed ovum pick-up (OPU) 36 hours after hCG injection (group B, 129 premature cycles), and LH surge with ear...

Two experiments were conducted to test the hypothesis that cortisol interferes with the positive feedback action of estradiol that induces the luteinizing hormone (LH) surge. Ovariectomized sheep were treated sequentially with progesterone and estradiol to create artificial estrous cycles. Cortisol or vehicle (saline) was infused from 2 h before the estradiol stimulus through the time of the an...

A central event in mammalian reproduction is the LH surge that induces ovulation and corpus luteum formation. Typically, the LH surge is initiated in ovariectomized rats by sequential treatment with estrogen and progesterone (PROG). The traditional explanation for this paradigm is that estrogen induces PROG receptors (PR) that are activated by exogenous PROG. Recent evidence suggests that where...

The preovulatory GnRH/LH surge in the ewe is stimulated by a rise in the circulating estradiol concentration that occurs in conjunction with preovulatory ovarian follicle development. In the presence of high levels of progesterone, such as during the luteal phase of the estrous/menstrual cycle, the stimulatory effects of elevated estradiol on GnRH/LH secretion are blocked. Recent work in the ew...

We tested the working hypothesis that Fos will identify the critical population of kisspeptin neurons that accompanies the LHRH surge using a synchronized follicular phase model in intact cycling ewes. The model generates an LH surge that starts within a defined 2-h window in a 20-d synchronized cycle. With a modified push-pull cannula in vivo LHRH release from the median eminence was sampled i...

Galanin mRNA levels in GnRH neurons increase in association with a steroid-induced LH surge in female rats. Both the steroid-induced LH surge and the concomitant increase of galanin mRNA in GnRH neurons are blocked by non-specific inhibition of central nervous system activity imposed by pentobarbital and specific central alpha-adrenergic receptor blockade. Based on these observations, we hypoth...

Background: To study the effectiveness of Clomiphene citrate (CC) in preventing a premature LH surge during controlled ovarian stimulation in women undergoing assisted reproduction. Materials and Methods: Couples were randomized to receive human menopausal gonadotrophins (hMG) followed by CC or hMG alone till the day of hCG. The primary outcomes were the incidence of a clinical pregnancy and pr...