Characterization of the LH Surge in Middle-Aged Female Rats1

Rl, Cooper; Pm, Conn; Rf, Walker

doi:10.1095/biolreprod23.3.611

Cited by 152 publications

(67 citation statements)

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“…One of the first signs of reproductive aging is a reduction in the magnitude of the LH surge (Cooper et al, 1980;Nass et al, 1984;Wise, 1982), which is followed by irregular estrous cycles suggesting impaired estrogen positive feedback. Eventually, the rat becomes acyclic, exhibiting a cornified vaginal cytology -a persistent or constant estrous state (CE).…”

Section: Menopausementioning

confidence: 99%

Estradiol regulation of progesterone synthesis in the brain

Micevych

Sinchak

2008

Molecular and Cellular Endocrinology

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Steroidogenesis is now recognized as a global phenomenon in the brain, but how it is regulated and its relationship to circulating steroids of peripheral origin have remained more elusive issues. Neurosteroids, steroids synthesized de novo in nervous tissue, have a large range of actions in the brain, but it is only recently that the role of neuroprogesterone in the regulation of arguably the quintessential steroid dependent neural activity, regulation of the reproduction has been appreciated. Circuits involved in controlling the LH surge and sexual behaviors were thought to be influenced by estradiol and progesterone synthesized in the ovary and perhaps the adrenal. It is now apparent that estradiol of ovarian origin regulates the synthesis of neuroprogesterone, and it is the locally produced neuroprogesterone that is involved in the initiation of the LH surge and subsequent ovulation. In this model, estradiol induces the transcription of progesterone receptors while stimulating synthesis of neuroprogesterone. Although the complete signaling cascade has not been elucidated, many of the features have been characterized. The synthesis of neuroprogesterone occurs primarily in astrocytes and requires the interaction of membrane associated estrogen receptor-α with metabotropic glutamate receptor-1a. This G protein-coupled receptor activates a phospholipase C that in turn increases inositol trisphosphate (IP 3 ) levels mediating the release of intracellular stores of Ca 2+ via an IP 3 receptor gated Ca +2 channel. The large increase in free cytoplasmic Ca 2+ ([Ca 2+ ] i ) stimulates the synthesis of progesterone, which can then diffuse out of the astrocyte and activate estradiol-induced progesterone receptors in local neurons to trigger the neural cascade to produce the LH surge. Thus, it is a cooperative action of astrocytes and neurons that is needed for estrogen positive feedback and stimulation of the LH surge.

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Section: Menopausementioning

confidence: 99%

Estradiol regulation of progesterone synthesis in the brain

Micevych

Sinchak

2008

Molecular and Cellular Endocrinology

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“…Elder women and female mammals show a decline in reproductive function with irregular menstrual and estrous cycles, ovulatory disturbance and decrease in fertility (Cooper et al, 1980;Dunson et al, 2004;Matt et al, 1998;Nass et al, 1984;Weiss et al, 2004). Rats are widely used in reproductive and developmental toxicity studies to evaluate the effects of pharmaceuticals and chemicals on the estrous cycle, fertility and the development of embryos/fetuses.…”

Section: Introductionmentioning

confidence: 99%

Maternal age and reproductive function in female Sprague-Dawley rats

et al. 2012

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-We investigated the age-related changes in reproductive function in female rats of the Crl:CD(SD) strain. The estrous cycles were monitored from 6 to 42 weeks of age. Other females were mated with males at 6, 8, 10, 15, 19, 23, 27, 31, 35 and 40 weeks of age and caesarean section was performed on day 20 of gestation to examine their fetuses, and then reproductive parameters were calculated and fetal growth was observed. The percentage of rats exhibiting irregular estrous cycles increased from 23 weeks of age. The copulatory and fertility indices decreased from 35 and 27 weeks of age, respectively. Dams at 6 weeks of age showed low numbers of corpora lutea and implantation sites. Although the number of corpora lutea was not affected by advanced maternal age, number of implantation sites decreased from 27 weeks of age. The pre-and post-implantation loss rates increased from 23 and 31 weeks of age, respectively, and the number of live fetuses decreased from 27 weeks of age. Fetal growth retardation was observed in maternal rats older than 31 weeks of age. The external observations on the fetuses revealed umbilical hernia at 35 to 40 weeks of age. These data indicated that maternal aging affected reproductive function and fetal development from 23 and 31 weeks of age, respectively. It was considered that the appropriate age of Crl:CD(SD) female rats for the assessment of reproductive toxicity were 8 to 22 weeks.

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“…The hypothalamus becomes less sensitive to positive oestrogen-feedback in older rats, which may result in a lower prooestrous surge of luteinizing hormone (LH) (Gray et al, 1980). It has also been reported that the LH-surge is delayed for some hours in middle-aged rats (Cooper et al, 1980;Wise, 1982).…”

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confidence: 99%

Quantification and classification of pregnancy wastage in 5-day cyclic young through middle-aged rats

Mattheij

Swarts

1991

Lab Anim

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SummaryFecundity was quantified in 4 to ll-month old rats with regular 5-day cycles. On the day following mating, less than 5% luteinized unruptured follicles occurred in either 4-month old or ll-month old rats; ovulation rate and also fertilization rate were similar in these young and middle-aged rats. At day 19 of pregnancy embryonic and fetal mortalities were quantified. Pregnancy wastage increased gradually with age; it was already significant in 7-month old rats. In rats of 9 months old it was about 30070 and in ll-month old rats it was greater than 65%. Pregnancy wastage was mainly due to preimplantation and early-postimplantation mortality. Pregnancy wastage did not decrease when the pre-ovulatory surge of luteinizing hormone (LH) was reinforced and timed, by injection of the LH-releasing hormone analogue Ovalyse at noon on the day of prooestrus. The results corroborate the idea that pregnancy wastage in middle-aged rats with regular cycles is caused by an age-related reduction of the viability of ovulating eggs.

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Characterization of the LH Surge in Middle-Aged Female Rats1

Cited by 152 publications

References 0 publications

Estradiol regulation of progesterone synthesis in the brain

Estradiol regulation of progesterone synthesis in the brain

Maternal age and reproductive function in female Sprague-Dawley rats

Quantification and classification of pregnancy wastage in 5-day cyclic young through middle-aged rats

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