Time-dependent ovulation-blocking effect of ether anesthesia was investigated using female Wistar-Imamichi rats showing a 4-day cycling rhythm. A 6-hr (1400-2000) and 8-hr (1400-2200) anesthesia with ether vapor on proestrus caused ovulation blockade in 85% and 100% of the rats, respectively. On the other hand, pentobarbital injections at 1400 and 1500 completely blocked the spontaneous ovulati...

A short lesson in endocrinology may help answer this question. GnRH is the abbreviation for gonadotropin releasing hormone, a natural hormone that is released from the hypothalamus in the brain. GnRH causes the release of two other hormones known as gonadotropins from the pituitary gland. Luteinizing hormone (LH) and follicle stimulating hormone (FSH) are the gonadotropins. During the normal es...

Gonadotropin-releasing hormone (GnRH) neurons increase their expression of Fos and galanin coincident with the luteinizing hormone (LH) surge in the female rat. To define the temporal relationships between the expression of these genes and the GnRH gene itself and to gain insight about the possible functional interactions of these processes, we compared levels of c-fos, galanin, and GnRH mRNA i...

Preovulatory LH and FSH surges and the subsequent periovulatory FSH surge were studied in heifers treated with a single injection of GnRH (100 microg, n = 6) or saline (n = 7). Blood samples were collected every hour from 6 h before treatment until 12 h after the largest follicle reached > or =8.5 mm (expected beginning of follicular deviation). The GnRH-induced preovulatory LH and FSH surges w...

In the elephant, two distinct LH surges occur 3 wl< apart during the nonluteal phase of the estrous cycle, but only the second surge (ovLH) induces ovulation. The function of the first, anovulatory surge (anLH) is unknown, nor is it clear what regulates the timing of these two surges. To further study this observation in the Asian elephant, serum concentrations of LH, FSH, progesterone, inhibin...

Hormone patterns in blood plasma were examined in relation to the bovine oestrous cycle in two experiments. During the luteal phase LH pulse frequency was low (2-3 pulses per 8 h). There were no consistent correlations between LH, FSH and progesterone concentrations. During luteolysis, falling progesterone concentrations were accompanied by an increase in oestradiol-17 beta concentrations, LH c...

Kisspeptin, encoded by Kiss1, stimulates GnRH neurons to govern reproduction. In rodents, estrogen-sensitive kisspeptin neurons in the anterior ventral periventricular nucleus and neighboring periventricular nucleus are thought to mediate sex steroid-induced positive feedback induction of the preovulatory LH surge. These kisspeptin neurons coexpress estrogen and progesterone receptors and displ...

Atrazine (ATR) blunts the hormone-induced luteinizing hormone (LH) surge, when administered by gavage (50-100 mg/kg/day for 4 days), in ovariectomized rats. In this study, we determined if comparable doses delivered either by gavage (bolus dose) or distributed in diet would reduce the LH surge and subsequently affect fertility in the intact female rat. ATR was administered daily to intact femal...

Kisspeptin and its receptor GPR54 have recently been identified as key signaling partners in the neural control of fertility in animal models and humans. The gonadotropin-releasing hormone (GnRH) neurons represent the final output neurons of the neural network controlling fertility and are suspected to be the primary locus of kisspeptin-GPR54 signaling. Using mouse models, the present study add...