Changes in LH pulse frequency and amplitude in intact mares during the transition into the breeding season

Fitzgerald, B. P.; Affleck, Karen; Barrows, Susan; Murdoch, W L; Barker, Kenneth N.; Loy, R. G.

doi:10.1530/jrf.0.0790485

Cited by 44 publications

(9 citation statements)

References 16 publications

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“…Fluctuations or surges superimposed on the hourly circulating concentrations of the periovulatory FSH surge in individuals beginning after the peak and before an 8.5 mm F1 were differentiated from variation due to extraneous factors (e.g. variation in assaying technique) as described (Fitzgerald et al 1985). (See below for definition of F1 and F2.)…”

Section: End Point Saline Gnrhmentioning

confidence: 99%

Relationships between FSH patterns and follicular dynamics and the temporal associations among hormones in natural and GnRH-induced gonadotropin surges in heifers

Haughian¹,

Ginther²,

Kot³

et al. 2004

Reproduction

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Preovulatory LH and FSH surges and the subsequent periovulatory FSH surge were studied in heifers treated with a single injection of GnRH (100 mg, n 5 6) or saline (n 5 7). Blood samples were collected every hour from 6 h before treatment until 12 h after the largest follicle reached $ 8.5 mm (expected beginning of follicular deviation). The GnRH-induced preovulatory LH and FSH surges were higher at the peak and shorter in duration than in controls, but the area under the curve was not different between groups. The profiles of the preovulatory LH and FSH surges were similar within each treatment group, suggesting that the two surges involved a common GnRH-dependent mechanism. Concentrations of FSH in controls at the nadir before the preovulatory surge and at the beginning and end of the periovulatory surge were not significantly different among the three nadirs. A relationship between variability in the periovulatory FSH surge and number of 5.0 mm follicles was shown by lower FSH concentrations during 12 -48 h after the beginning of the surge in heifers with more follicles (11.0 6 1.0 follicles (mean6S.E.M.) n 5 7) than in heifers with fewer follicles (5.7 6 0.4, n 5 6). This result was attributed to increased FSH suppression from increased numbers of follicles reaching 5.0 mm. Grouping of heifers into those with longer vs shorter intervals from a 4.5 mm to an 8.5 mm largest follicle did not disclose any relationship between length of the interval and FSH characteristics (e.g. profile of surge, area under curve, FSH concentrations at specific events). The hypothesis of a relationship between variation in the periovulatory FSH surge and variation in follicular dynamics was supported for the number of 5.0 mm follicles but not for the hour the largest follicle reached 8.5 mm. Thus, the expected time of follicle deviation was not altered by the extensive variation in the wave-stimulating FSH surge.

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Section: End Point Saline Gnrhmentioning

confidence: 99%

Relationships between FSH patterns and follicular dynamics and the temporal associations among hormones in natural and GnRH-induced gonadotropin surges in heifers

Haughian¹,

Ginther²,

Kot³

et al. 2004

Reproduction

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“…During long days the inhibitory action of melatonin on the mare's reproductive axis is lifted and increased gonadotropin releasing hormone pulse frequency stimulates the anterior pituitary to release follicle stimulating hormone and luteinising hormone, which act in concert to promote the growth, development and ovulation of ovarian follicles .…”

Section: Introductionmentioning

confidence: 99%

Blue light from individual light masks directed at a single eye advances the breeding season in mares

Murphy

Walsh

Woodward

et al. 2013

Equine Veterinary Journal

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“…How day length and its melatonin signal are translated into a change in GnRH pulse generator activity is unknown. In the seasonally anestrous mare, investigators have shown that LH and FSH pulse frequency is very low [Fitzgerald et al, 1987;Thompson et al, 1987], but that it gradually increases together with the LH:FSH ratio as the mare makes the transition into the breeding season . On the other hand, the termination of the breeding season is marked by failure of preovulatory follicles to ovulate; this implies inadequate LH, possibly due to failure to increase GnRH pulse generator activity following luteolysis [Snyder et al, 1979].…”

Section: Control Of Seasonal Breedingmentioning

confidence: 99%

The Nonpregnant Mare: A Review of Some Current Research and of the Last 25 Years of Endocrinology

Irvine

1995

Biology of Reproduction

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Changes in LH pulse frequency and amplitude in intact mares during the transition into the breeding season

Abstract: Summary. Two groups of mares were exposed to an abrupt, artificial increase or a natural increase in daylength.

Cited by 44 publications

References 16 publications

Relationships between FSH patterns and follicular dynamics and the temporal associations among hormones in natural and GnRH-induced gonadotropin surges in heifers

Relationships between FSH patterns and follicular dynamics and the temporal associations among hormones in natural and GnRH-induced gonadotropin surges in heifers

Blue light from individual light masks directed at a single eye advances the breeding season in mares

The Nonpregnant Mare: A Review of Some Current Research and of the Last 25 Years of Endocrinology

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