Oestrogen–bromocriptine interaction in the control of luteinizing hormone and prolactin secretion in the neonatally oestrogenized female rat

Aguilar, E.; Galaz, Carmen Fernandez; Vaticón, M. D.; Tejero, A.; Oriol, A

doi:10.1677/joe.0.0970319

Cited by 11 publications

(5 citation statements)

References 26 publications

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“…The alterations induced by neonatal administration of TP or OeB (acyclicity, anovulation, ovarian atrophy, and loss of negative and positive feedback between oestradiol and LH) are in accordance with a number of previous studies (Barraclough 1961, Gorski 1963, Mennin & Gorski 1975, Aguilar et al 1983. In addition, postnatal treatment of female rats with antioestrogens, such as ICI-628 or MER-25, has been shown to interfere with hypothalamic feminization (McEwen et al 1977, Döhler & Hancke 1978 and to prevent hypothalamic masculinization by oestrogens or androgens (Döhler & Hancke 1978).…”

Section: Discussionsupporting

confidence: 91%

Comparative effects of testosterone propionate, oestradiol benzoate, ICI 182,780, tamoxifen and raloxifene on hypothalamic differentiation in the female rat

Pinilla¹,

Barreiro²,

Gonzalez³

et al. 2002

Journal of Endocrinology

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Hypothalamic differentiation in the female rat during the neonatal period is critically dependent on the steroid milieu, as permanent changes in reproductive function are observed after administration of oestradiol and testosterone during such a critical stage. Selective oestrogen modulators (SERMs) constitute a family of drugs that, depending on the tissue, are able to exert oestrogenic or antioestrogenic actions. The present experiments were conducted to analyse whether the SERMs, tamoxifen and raloxifene, can cause oestrogenic actions during the hypothalamic differentiation period.Postnatal female rats were injected between days 1 and 5 with 100 µg/day tamoxifen, raloxifene or ICI 182,780 (a pure antioestrogen). Other groups of animals were injected on day 1 of age with 100 µg oestradiol benzoate (OeB) or 1·25 mg testosterone propionate (TP) alone or in combination with raloxifene (500 µg/day between days 1 and 5). In all experimental groups, the age, body weight and concentrations of serum gonadotrophins at vaginal opening were recorded, whereas vaginal cyclicity and the negative and positive feedback between oestradiol and LH were monitored in adulthood.The results obtained confirmed the ability of high doses of OeB or TP to alter the normal differentiation of the brain permanently. They also reinforced the hypothesis that oestrogens are also necessary for normal brain differentiation in female rats because administration of a pure antioestrogen, such as ICI 182,780 permanently altered the function of the reproductive axis. In addition, our data provided evidence for different actions of the two SERMs under analysis (raloxifene and tamoxifen) upon peripheral targets, as raloxifene advanced vaginal opening whereas tamoxifen did not. In contrast, their actions on brain differentiation appeared similar and analogous to those obtained after neonatal administration of oestradiol, as evidenced by vaginal acyclicity, ovarian atrophy, sterility and abolition of negative and positive feedback between oestradiol and LH, thus suggesting an oestrogenic action of these SERMs on hypothalamic differentiation. Moreover, the oestrogenic activity of raloxifene was supported by its inability to block the effects of OeB and TP administered neonatally.In conclusion, the present results indicated that the SERMs, tamoxifen and raloxifene, exert an oestrogen-like effect upon hypothalamic differentiation of the neonatal female rat.

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Section: Discussionsupporting

confidence: 91%

Comparative effects of testosterone propionate, oestradiol benzoate, ICI 182,780, tamoxifen and raloxifene on hypothalamic differentiation in the female rat

Pinilla¹,

Barreiro²,

Gonzalez³

et al. 2002

Journal of Endocrinology

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“…In fact the hyperprolactinaemia in SH rats is accompanied by increased plasma concentrations of FSH (Amador et al 1983), while the greater increase in prolactin levels in grafted or tumour-bearing rats suppress gonadotrophin secretion (Bartke, Smith, Michael et al 1977;Hodson, Simpkins, Pass et al 1980). In addition, in neonatally oestrogenized adult female rats, hyperprolactinaemia with high (Vaticón, Aguilar, Fernandez-Galaz & Tejero, 1980) or normal (Aguilar, Fernandez-Galaz, Vaticón et al 1983) plasma levels of LH have been reported.…”

Section: Discussionmentioning

confidence: 99%

Secretion of LH in spontaneously hypertensive rats

Rodriguez-Padilla¹,

Bellido²,

Pinilla³

et al. 1987

Journal of Endocrinology

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Weights of testes, seminal vesicles, ventral prostate and pituitary, plasma testosterone and LH concentrations, pituitary LH content and concentration, the LH in-vivo response after LHRH administration (1 microgram), and basal and LHRH-stimulated secretion in vitro were analysed in adult male spontaneously hypertensive (SH) and normotensive control (WKY) rats. Spontaneously hypertensive rats showed: testis and pituitary hypertrophy; seminal vesicle and ventral prostate atrophy; increased plasma testosterone and LH concentrations; increased pituitary LH content and concentration; unchanged net increase of plasma concentrations of LH 15 and 45 min after administration of 1 microgram LHRH; and increased basal LH secretion in vitro with a normal response to LHRH stimulation. These results provide evidence that SH rats show increased LH secretion with a normal response to LHRH stimulation. The coexistence of high plasma concentrations of testosterone with seminal vesicle and ventral prostate atrophy suggest a reduction in the effectiveness of testosterone in these structures.

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“…In addition, perinatal life is the period of greatest sensitivity to the organizing effects of gonadal steroids [8,14], and large doses of estrogens given s.c. to neonate rats result in neuroendocrine alterations [15,16] that resemble those observed in spontaneously aging females already in constant estrus [6,7]. Thus, to reproduce the conditions that cause early reproductive senescence, small doses of steroids have been administered early in life with the result that the animals displayed regular estrus cycles after puberty but soon failed to ovulate [14,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…Based on this hypothesis, a first alternative approach was therefore designed to determine whether a controlled neonatal exposure to a large dose of E 2 by means of implants is sufficient to improve the results obtained with low doses by s.c. injections. Thus, to assess the optimal duration of the treatment that will lead to DAS, we examined the effects of gradual reduction of EB exposure time, using a dose (100 pLg) previously shown to produce a full anovulatory syndrome when given s.c. [15,16,20].…”

Section: Introductionmentioning

confidence: 99%

Controlled Neonatal Exposure to Estrogens: A Suitable Tool for Reproductive Aging Studies in the Female Rat1

Rodriguez

Fernández-Galaz

Tejero

1993

Biology of Reproduction

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The present study was designed to determine whether the modification of exposure time to large doses of estrogens provided a reliable model for early changes in reproductive aging. Silastic implants containing estradiol benzoate (EB) in solution were placed into 5-day-old female Wistar rats and removed 1 day (Ei1 group) or 5 days (Ei5) later. In addition, 100 micrograms [corrected] EB dissolved in 100 microliters corn oil was administered s.c. to another group (EI). Control rats received either vehicle implants or 100 microliters corn oil. Premature occurrence of vaginal opening was observed in all three estrogenized groups independently of EB exposure. However, females bearing implants for 24 h had first estrus at the same age as their controls and cycled regularly, and neither histological nor gonadal alterations could be observed at 75 days. Interestingly, they failed to cycle regularly at 5 mo whereas controls continued to cycle. On the other hand, the increase of EB exposure (Ei5, EI) resulted in a gradual and significant delay in the onset of first estrus and in a high number of estrous phases, as frequently observed during reproductive decline. At 75 days, the ovaries of these last two groups showed a reduced number of corpora lutea and an increased number of large follicles. According to this histological pattern, ovarian weight and progesterone (P) content gradually decreased whereas both groups showed higher estradiol (E2) content than controls. This resulted in a higher E2:P ratio, comparable to that observed in normal aging rats.(ABSTRACT TRUNCATED AT 250 WORDS)

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Oestrogen–bromocriptine interaction in the control of luteinizing hormone and prolactin secretion in the neonatally oestrogenized female rat

Cited by 11 publications

References 26 publications

Comparative effects of testosterone propionate, oestradiol benzoate, ICI 182,780, tamoxifen and raloxifene on hypothalamic differentiation in the female rat

Comparative effects of testosterone propionate, oestradiol benzoate, ICI 182,780, tamoxifen and raloxifene on hypothalamic differentiation in the female rat

Secretion of LH in spontaneously hypertensive rats

Controlled Neonatal Exposure to Estrogens: A Suitable Tool for Reproductive Aging Studies in the Female Rat1

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