Reproductive Endocrinology in Hatano High- and Low-Avoidance Rats During the Estrous Cycle

Asai, Sayaka; Ohta, Ryo; Shirota, Mariko; Satô, Masako; Watanabe, Gen; Taya, Kazuyoshi

doi:10.1385/endo:18:2:161

Cited by 15 publications

(31 citation statements)

References 21 publications

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“…The number of oocytes shed at first ovulation in HAAs was significantly larger than that of LAAs. A similar difference was also observed between adult cyclic HAAs and LAAs (Asai et al 2002). Thus, HAAs ovulate more oocytes than LAAs from the first estrus.…”

Section: Discussionsupporting

confidence: 72%

“…Thus, HAAs ovulate more oocytes than LAAs from the first estrus. Size-fractionated comparisons of ovarian follicles between adult HAAs and LAAs revealed that a greater number of large antral follicles had developed in HAA ovaries by noon of the day of proestrus as compared with LAAs (Asai et al 2002). In contrast, no differences in the numbers of oocytes shed at the induced ovulation were found between immature HAAs and LAAs, and the number in LAAs was comparable to that counted at the first ovulation.…”

Section: Discussionmentioning

confidence: 82%

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Minor involvement of somatic growth in the onset of puberty of Hatano high- and low-avoidance rats

Shirota¹,

Satô²,

Kojima³

et al. 2004

Reproduction

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The present study was planned to examine the effects of somatic growth on the determination of timing of puberty using Hatano high-and low-avoidance rats (HAAs and LAAs); the rats were genetically selected from Sprague-Dawley (SD) rats for good or poor performance in a two-way active avoidance-learning test. Since these two lines were found to have different characteristics, such as body weight at birth, maternal care and timing of male puberty, the present study characterized female puberty in Hatano rats and then compared postnatal growth and timing of puberty between the two lines of rats when they were nursed by foster SD dams. When nursed under biological dams, HAAs became heavier, exhibited vaginal opening at a younger age and first ovulation was accompanied by more oocytes than LAAs. In all of the HAAs, but none of the LAAs, ovulation was induced by a single s.c. injection of 5 IU equine chorionic gonadotropin (eCG) on day 22 after birth. An additional treatment with 10 IU human CG revealed that, in the ovaries of LAAs, a small number of follicles had developed to an ovulable stage as a result of the treatment. The fostering improved somatic growth, and weights of LAAs were sustained at a heavier level than those of fostered HAAs. The fostering, however, did not eliminate the line difference in the timing of puberty of both sexes; it did accelerate the vaginal opening of LAAs but not the balanopreputial separation. Thus, there is a phenotypic difference in the timing of female puberty in Hatano rats exhibiting a different timing of ovarian development in response to gonadotropin. The present study indicates that postnatal somatic growth is not the predominant determinant in the onset of puberty in Hatano rats.

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Section: Discussionsupporting

confidence: 72%

Section: Discussionmentioning

confidence: 82%

Minor involvement of somatic growth in the onset of puberty of Hatano high- and low-avoidance rats

Shirota¹,

Satô²,

Kojima³

et al. 2004

Reproduction

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“…Milk yield was significantly lower in LAA rats than in HAA rats. Our previous report showed LAA pups with reduced weight gain compared with HAA pups (Ohta et al 1998), LAA dams with a lowered prolactin secretion 15 min after suckling compared with HAA rats, and LAA dams with a lowered milk yield during a 15-min period of suckling compared with HAA dams (Ohta et al 2002). We also reported that there were no strain differences in the levels of milk ejection following oxytocin injection between HAA and LAA rats (Ohta et al 2002).…”

Section: Discussionmentioning

confidence: 47%

“…Adrenal weights are heavier in HAA rats than in LAA rats, and plasma concentrations of ACTH are higher in HAA rats than in LAA rats (Ohta et al 1999). HAA rats and LAA rats show differences in follicular development, luteal function and pattern of hormonal secretion during the oestrous cycle (Asai et al 2002). The body weights of the HAA pups are heavier than the LAA pups during the latter half of lactation.…”

Section: Introductionmentioning

confidence: 93%

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Endocrinological responses during suckling in Hatano high- and low-avoidance rats

Asai¹,

Ohta²,

Shirota³

et al. 2004

Journal of Endocrinology

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Hatano high-avoidance (HAA) and low-avoidance (LAA) animals were originally selected from Sprague-Dawley rats for good and poor active avoidance learning in a shuttle box. We studied the endocrinological profile in lactating rats to determine the effect of suckling during midlactation in HAA and LAA rats. The pups were separated from their mother rats 6 h before the onset of suckling and blood samples were drawn from unanaesthetized mother rats via a jugular cannula at 0, 5 and 15 min after the suckling stimulus and then 15, 45 and 105 min after pups were removed.Plasma concentrations of oxytocin in HAA rats were significantly higher than in LAA rats during the suckling period. Plasma concentrations of prolactin and ACTH in HAA rats were significantly higher than in LAA rats during the suckling period, and at 15 min and 45 min after the pups were removed. However, there were no strain differences in circulating corticosterone between the two lines, indicating that the response of the hypothalamopituitary axis to the suckling stimulus was greater in HAA rats than in LAA rats, whereas the ACTH-induced adrenal response of corticosterone release was higher in LAA rats than in HAA rats. Since dopamine from the median eminence inhibits prolactin secretion from the lactotrophs of the anterior pituitary, and tuberoinfundibular dopaminergic neurones are partially regulated by the level of circulating prolactin, we evaluated the activity of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine biosynthesis. TH, measured by the accumulation of 3,4-dihydroxyphenylalanine, was significantly higher in HAA rats than in LAA rats before the suckling stimulus. After the suckling stimulus, TH activity in HAA rats was significantly lower than before suckling, whereas TH activity in LAA rats was not changed.These findings clearly demonstrated that apparent differences between the two Hatano lines exist in endocrinological profiles during suckling. These strain differences probably originate from neurotransmitter changes, such as dopamine.

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Tolerance to vitrification of rat embryos at various developmental stages

Taketsuru

Kaneko

2018

Cryobiology

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Reproductive Endocrinology in Hatano High- and Low-Avoidance Rats During the Estrous Cycle

Cited by 15 publications

References 21 publications

Minor involvement of somatic growth in the onset of puberty of Hatano high- and low-avoidance rats

Minor involvement of somatic growth in the onset of puberty of Hatano high- and low-avoidance rats

Endocrinological responses during suckling in Hatano high- and low-avoidance rats

Tolerance to vitrification of rat embryos at various developmental stages

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