Postpartum Preovulatory Surge of Gonadotropin Secretion in the Rat May Be Initiated by the Labor Process
1

Fox, Susan; Smith, M. Susan

doi:10.1095/biolreprod31.4.619

Cited by 14 publications

(12 citation statements)

References 23 publications

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“…Postpartum estrus commonly occurs 1 or 2 days after parturition in Mongolian gerbils [18]. The process of parturition actively contributes to the stimulation of the postpartum gonadotropin surges [5]. From day 1 to day 3 of lactation, high levels of gonadotropin correlated with post-partum ovulation in Mongolian gerbils, which is a result similar to that reported for rats [2,8,21].…”

Section: Hormonal Variations During Lactation In Primiparous Mongoliasupporting

confidence: 65%

Variations in Serum Gonadotropin and Prolactin Levels during Consecutive Reproductive States in Mongolian Gerbils (Meriones unguiculatus)

Shi

2011

Exp. Anim.

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Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL) levels were examined during consecutive reproductive states in Mongolian gerbils. The results indicate that FSH, LH, and PRL levels peak at proestrus, estrus, and diestrus, respectively. During early gestation in primiparous gerbils, gonadotropin levels were the lowest on day 6. This was followed by an increase in FSH and LH levels until days 18 and 15, respectively, with levels remaining constant until day 21. However, in multiparous gerbils, gonadotropin levels were the lowest on day 12 of gestation and were relatively stable between days 15 to 21. In both primiparous and multiparous gerbils, gonadotropin levels increased rapidly from day 21 of gestation to day 3 of lactation, and kept stable between 6-24 days of lactation. PRL peaked during early gestation on days 9 and 6 in the primiparous and multiparous gerbils, respectively, followed by a decline. PRL levels subsequently peaked again on day 21 before parturition. During lactation, PRL levels peaked on days 6 and 9 in primiparous and multiparous gerbils, respectively, followed by a decline until lactation ended. These findings suggest that variations in gonadotropin during the estrous cycle, gestation, and lactation in Mongolian gerbils are similar to those observed in rats, whereas prolactin levels differ. Changes in gonadotropin and prolactin levels during different reproductive states were found to be similar in primiparous and multiparous gerbils, and were correlated with the reproductive stages of Mongolian gerbils.

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Section: Hormonal Variations During Lactation In Primiparous Mongoliasupporting

confidence: 65%

Variations in Serum Gonadotropin and Prolactin Levels during Consecutive Reproductive States in Mongolian Gerbils (Meriones unguiculatus)

Shi

2011

Exp. Anim.

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“…The corpus luteum is active in secretion of progesterone throughout the lactating period as described later. The postpartum LH surge is considered to be induced by the expansion of the vaginal cervix associated with parturition, because when the pups are taken out by cesarian incision, the postpartum LH surge and subsequent ovulation do not occur (Fox and Smith, 1984).…”

Section: Postpartum Ovulationmentioning

confidence: 99%

Physiology of Reproduction

2000

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“…It has been shown that stimuli that are not ordinarily required become necessary for estrogeninduced LH surges under specific physiological conditions. Fox & Smith (1984) found that LH surges that normally occur in the afternoon on the day of parturition were blocked when pups were delivered by cesarean section, and that uterine cervical stimulation in the morning restored the LH surges in these cesarean-sectioned rats. They suggested that the post Figure 3 Effect of pup removal on progesterone-induced LH surges in lactating rats.…”

Section: Discussionmentioning

confidence: 91%

Pup removal suppresses estrogen-induced surges of LH secretion and activation of GnRH neurons in lactating rats

Fukushima¹,

Yin²,

Ishida³

et al. 2006

Journal of Endocrinology

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During lactation, the suckling stimulus exerts profound influences on neuroendocrine regulation in nursing rats. We examined the acute effect of pup removal on the estrogeninduced surge of LH secretion in ovariectomized lactating rats. Lactating and nonlactating cyclic female rats were given an estradiol-containing capsule after ovariectomy, and blood samples were collected through an indwelling catheter for serum LH determinations. In lactating, freely suckled ovariectomized rats, estrogen treatment induced an afternoon LH surge with a magnitude and timing comparable to those seen in nonlactating rats. Removal of pups from the lactating rats at 0900, 1100, or 1300 h, but not at 1500 h, suppressed the estrogen-induced surge that normally occurs in the afternoon of the same day. The suppressive effect of pup removal at 0900 h was completely abolished when the pups were returned by 1400 h. In contrast, pup removal was ineffective in abolishing the stimulatory effect of progesterone on LH surges. Double immunohistochemical staining for gonadotropinreleasing hormone (GnRH) and c-Fos, a marker for neuronal activation, revealed a decrease, concomitantly with the suppression of LH surges, in the number of c-Fos-immunoreactive GnRH neurons in the preoptic regions of nonsuckled rats. An LH surge was restored in nonsuckled rats when 0$1 mg oxytocin was injected into the third ventricle three times at 1-h intervals during pup removal. These results suggest that the GnRH surge generator of lactating rats requires the suckling stimulus that is not involved in nonlactating cyclic female rats.

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Postpartum Preovulatory Surge of Gonadotropin Secretion in the Rat May Be Initiated by the Labor Process 1

Abstract: These studies attempted

Cited by 14 publications

References 23 publications

Variations in Serum Gonadotropin and Prolactin Levels during Consecutive Reproductive States in Mongolian Gerbils (Meriones unguiculatus)

Variations in Serum Gonadotropin and Prolactin Levels during Consecutive Reproductive States in Mongolian Gerbils (Meriones unguiculatus)

Physiology of Reproduction

Pup removal suppresses estrogen-induced surges of LH secretion and activation of GnRH neurons in lactating rats

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