The ferret is a reflex-ovulating species in which receipt of an intromission induces a prolonged (612 h) preovulatory LH surge in the estrous female. This LH surge is probably stimulated by a large release of GnRH from the mediobasal hypothalamus (MBH). In Exp 1 we asked whether GnRH messenger RNA (mRNA) levels increase in response to mating so as to replenish the MBH GnRH stores needed to sust...

Homozygous androgen receptor (AR)-knockout (ARKO) female mice are subfertile due to both intra- and extraovarian (neuroendocrine) defects as defined by ovary transplantation. Using ARKO mice, this study set out to reveal the precise AR-regulated pathways required for optimal androgen-regulated ovulation and fertility. ARKO females exhibit deficient neuroendocrine negative feedback, with a reduc...

The multiple control of gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) secretion involves locus coeruleus (LC) and neuropeptide Y (NPY). The objective of the present study was to analyze the possible contribution of the LC to the control of NPY activity in the medial basal hypothalamus (MBH) and medial preoptic area (MPOA) during the LH surge induced by estrogen (E(2)) and proge...

Since structural luteolysis involves deterioration of tissue, the gene expression of matrix-metalloproteinase-1 (MMP-1) and the respective tissue inhibitor of this metalloprotease (TIMP-1) were measured at various times on the day of pro-oestrus and in animals in which the preovulatory prolactin surge was blocked for the duration of 3 cycles by bromocriptine. An additional group of prolactin-bl...

AIMS AND OBJECTIVE To evaluate the role of GnRH antagonist in prevention of premature LH surge and increasing pregnancy rates in IUI cycle with mild ovarian hyperstimulation (MOH). STUDY DESIGN Prospective parallel, randomised controlled study. MATERIAL AND METHODS Couples diagnosed with unexplained, male factor subfertility and with one or both tubes patent were randomised to receive eithe...

Sir, It has been more than 10 years since safe and effective gonadotrophinreleasing hormone (GnRH) antagonists became available for use in controlled ovarian stimulation (COS) cycles. In 2000, we noted that there was an inconsistency with how researchers in this field describe the mechanism of action of GnRH antagonists (Mannaerts and Gordon, 2000). Unfortunately, there is continued misuse of t...

Development of a controlled release formulation of gonadotropin releasing hormone that would stimulate a LH surge capable of reducing the time span of ovulations would greatly benefit reproductive management because a single timed insemination could be used. A dose-response study was conducted to determine if Deslorelin, a potent gonadotropin releasing hormone analogue, delivered via the SABER ...

The suprachiasmatic nucleus (SCN) controls the timing of the preovulatory LH surge in laboratory rodents. Barbiturate administration during a critical period on proestrus delays the surge and prolongs the estrous cycle one day. Because a non-photic timing signal (zeitgeber) during the critical period that phase advances activity rhythms can also induce the latter effect, we hypothesized that ba...

The aim of the present study was to examine the messenger RNA expressions of the endothelin and angiotensin systems during the periovulatory phase in gonadotrophin releasing hormone (GnRH)-treated cows. Ovaries were collected by transvaginal ovariectomy (n=5 cows/group), and the follicles (n=5, one follicle/cow) were classified into the following groups: before GnRH administration (control, bef...