Actions of gonadotropin-releasing hormone analogues in pituitary gonadotrophs and their modulation by ovarian steroids

Weiss, Johannes M.; König, Stephan J.; Polack, Stephan; Emons, Günter; Schulz, K.-D.; Diedrich, K.; Ortmann, O.

doi:10.1016/j.jsbmb.2006.06.009

Cited by 6 publications

(2 citation statements)

References 65 publications

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“…To further analyze the effect of delayed ovulation on embryo development, we established a mouse model in which the LH surge was suppressed by cetrorelix. This GnRH antagonist binds competitively to the same receptor as GnRH, and equimolar amounts of cetrorelix and GnRH lead to a complete suppression of LH secretion (16). This compound is one of the most advanced GnRH antagonists available to date, and it is commonly used to suppress LH surges in women in assisted reproductive technology (ART) programs (17).…”

mentioning

confidence: 99%

Hormone-induced delayed ovulation affects early embryonic development

Bittner¹,

Horsthemke²,

Winterhager³

et al. 2011

Fertility and Sterility

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mentioning

confidence: 99%

Hormone-induced delayed ovulation affects early embryonic development

Bittner¹,

Horsthemke²,

Winterhager³

et al. 2011

Fertility and Sterility

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“…This result suggests, that a single low (1 mg) dose does not cause downregulation of GnRH-R, however multiple low doses appear to impose a similar response to that of a single high (10 mg) dose. While it is documented that GnRH antagonists can competitively block GnRH-R without the desensitization or down-regulation of GnRH-R observed with GnRH agonists (Loumaye et al, 1984), there are nevertheless numerous reports concerning decreases in pituitary GnRH-R mRNA during pro-longed GnRH antagonist treatment (Weiss et al, 2006). Treatment with high doses of the GnRH antagonist cetrorelix have also produced considerable downregulation of pituitary GnRH-R expression in rats (Pinski et al, 1996).…”

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confidence: 99%

New insights into the reproductive physiology and management of the female koala (Phascolarctos cinereus): factors affecting the control of the oestrous cycle

Ballantyne¹

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The objective of this thesis was to investigate the factors controlling the reproductive cycle of the female koala and develop an oestrous synchronization technique to facilitate the further refinement and efficacy of artificial insemination (AI) in the koala. A component of this development was the establishment of less invasive strategies to accurately monitor the reproductive status of the female koala, without the need for physical restraint or serial venipuncture. Chapter 2 of this thesis evaluated the efficacy of faecal oestrogen analysis, combined with the detection of oestrous behaviour as a control, to monitor ovarian cycles. Whilst faecal oestrogens did not correlate well with plasma oestradiol-17β to allow for an accurate estimate of cycle length or indicate or predict the precise timing of oestrus, the individual mean faecal oestrogen concentrations did, however, show a strong relationship to the individual mean plasma oestradiol-17β concentrations for each koala; in addition total faecal oestrogens were significantly higher in cycling females (P = 0.007).Chapters 3 and 4 of this thesis examined factors controlling reproductive cyclicity in the female koala. The pattern of prolactin (Prl) secretion and its relationship to oestrous behaviour and pouch young (PY) development throughout lactation in the koala was investigated in C]hapter 3.Oestrous behaviour was suppressed throughout the majority of lactation despite basal levels of Prl during early lactation. Koalas returned to oestrus some 102 days before PY had reached independence. The koala anterior pituitary also remained responsive in terms of luteinizing hormone (LH) secretion to injections of mammalian gonadotrophin-releasing hormone (mGnRH) during periods of high and low Prl secretion. Chapter 4 investigated the seasonality of oestrous behaviour (oestrous cycle activity) in a captive koala population in Southeast Queensland (SEQ).Although some individual koalas in the population showed signs of oestrous behaviour throughout the year, an obvious seasonality was apparent with significantly less females displaying oestrous iii behaviour in late autumn and winter (May -August), than September to April (P < 0.0001). While average monthly photoperiod (P < 0.0001) and average monthly temperature (P < 0.0001) were associated with oestrous behaviour, rainfall was not (P = 0.097).Chapters 5 and 6 report studies which investigated techniques, designed to allow for the manipulation and planning of timed insemination of female koalas. The impact of the gonadotrophin-releasing hormone (GnRH) antagonist, azaline B on LH and ovarian steroid hormone secretion in response to stimulation with mGnRH and its potential application in an oestrous synchronization protocol in cycling koalas was examined in chapter 5. In experiment 1, single sub-cutaneous (SC) injections of azaline B successfully blocked the ability of the anterior pituitary (AP) to respond to exogenous mGnRH in a dose dependant manner: 0 mg (n = 4) did not suppress LH response, 1 mg (n = 6) su...

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Use of the gonadotrophin-releasing hormone antagonist azaline B to control the oestrous cycle in the koala (Phascolarctos cinereus)

Ballantyne

Anderson

Pyne

et al. 2016

Reprod. Fertil. Dev.

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The present study examined the effectiveness of the gonadotrophin-releasing hormone (GnRH) antagonist azaline B to suppress plasma LH and 17β-oestradiol concentrations in koalas and its potential application for oestrous synchronisation. In Experiment 1, single subcutaneous injections of azaline B successfully blocked the LH response to exogenous mammalian (m) GnRH in a dose-dependent manner; specifically, 0 mg (n = 4) did not suppress the LH response, 1 mg azaline B (n = 6) suppressed the LH response for 24 h (P < 0.05), 3.3 mg azaline B (n = 8) suppressed the LH response significantly in all animals only for 3 h (P < 0.05), although in half the animals LH remained suppressed for up to 3 days, and 10 mg azaline B (n = 4) suppressed the LH response for 7 days (P < 0.05). In Experiment 2, daily 1 mg, s.c., injections of azaline B over a 10-day period during seasonal anoestrus (June-July; n = 6) suppressed (P < 0.01) the LH response to mGnRH consecutively over the 10-day treatment period and, 4 days after cessation of treatment, the LH response had not recovered. Experiment 3 was designed to test the efficacy of daily 1 mg, s.c., azaline B over 10 days to suppress plasma LH and 17β-oestradiol concentrations and ultimately synchronise timed return to oestrus during the breeding season. Although azaline B treatment did not suppress basal LH or 17β-oestradiol, oestrus was delayed in all treated females by 24.2 days, but with high variability (range 9-39 days). Overall, the present study demonstrates that the GnRH antagonist azaline B is able to inhibit the LH response in koalas to exogenous mGnRH and successfully delay the return to oestrus. However, although azaline B clearly disrupts folliculogenesis, it has not been able to effectively synchronise return to oestrus in the koala.

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Actions of gonadotropin-releasing hormone analogues in pituitary gonadotrophs and their modulation by ovarian steroids

Cited by 6 publications

References 65 publications

Hormone-induced delayed ovulation affects early embryonic development

Hormone-induced delayed ovulation affects early embryonic development

New insights into the reproductive physiology and management of the female koala (Phascolarctos cinereus): factors affecting the control of the oestrous cycle

Use of the gonadotrophin-releasing hormone antagonist azaline B to control the oestrous cycle in the koala (Phascolarctos cinereus)

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