Estrogens Modulate the Circadian Rhythm of Hypothalamic Beta-Endorphin Contents in Female Rats

Genazzani, Ar; Trentini, G. P.; Cf, De Gaetani; Criscuolo, Mario; Ficarra, Guido; Bm, De Ramundo; Cleva, M.

doi:10.1159/000125589

Cited by 43 publications

(29 citation statements)

References 15 publications

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“…Twenty-four hours after the last treatment, each animal was euthanized by decapitation (on the same day) under deep pentobarbital anesthesia (30 mg/kg i.p. ), as previously described [15, 18]. Cycling control rats were sacrificed on the morning of proestrus, as verified by a vaginal smear.…”

Section: Methodsmentioning

confidence: 99%

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Progesterone and Medroxyprogesterone Acetate Effects on Central and Peripheral Allopregnanolone and Beta-Endorphin Levels

Bernardi¹,

Pluchino²,

Pieri³

et al. 2006

Neuroendocrinology

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The increased use of hormonal therapies has led to the study of the properties of different progestin molecules and their effects on the central nervous system. The central and peripheral levels of neurosteroid allopregnanolone and the opioid peptide β-endorphin (β-END) are regulated by estrogens. The aim of the present study was to investigate the effects of a 2-week oral treatment with micronized progesterone or medroxyprogesterone acetate (MPA) alone or in addition to estradiol valerate (E2V) on central and peripheral allopregnanolone and β-END levels in ovariectomized (OVX) female rats. Thirteen groups of Wistar OVX rats received one of the following treatments: oral progesterone (2, 4 or 8 mg/kg/day); oral MPA (0.05, 0.1 or 0.2 mg/kg/day); E2V (0.05 mg/kg/day); E2V + progesterone (0.05 mg/kg/day + 2, 4 or 8 mg/kg/day), or E2V + MPA (0.05 mg/kg/day + 0.05, 0.1 or 0.2 mg/kg/day) for 14 days. One group of fertile and one group of OVX rats were used as controls. The concentration of allopregnanolone was assessed in the frontal and parietal lobes, hypothalamus, hippocampus, anterior pituitary, adrenals and serum, while the β-END content was assessed in the frontal and parietal lobes, hypothalamus, hippocampus, anterior and neurointermediate pituitary, and plasma. E2V administration reverted the ovariectomy-induced reduction in allopregnanolone and β-END. Progesterone and MPA increased allopregnanolone levels in all tissues except in the adrenal gland. The combined administration of progesterone or MPA and E2V determined a further increase in allopregnanolone levels with respect to E2V alone except in the adrenal gland and hippocampus only after MPA treatment. Progesterone did not affect β-END levels in the frontal and parietal lobes, hippocampus and anterior pituitary, while it caused an increase plasma, hypothalamic and neurointermediate pituitary β-END levels. MPA only affected β-END levels in the hippocampus and in the neurointermediate lobe. The combined administration of progesterone or MPA and E2V did not alter the effect of estradiol or it determined a further dose-dependent increase in β-END levels. In conclusion, this study demonstrates that progesterone and MPA have a similar but not identical effect on central and peripheral allopregnanolone and β-END levels. Their association with an estrogenic compound does not interfere with the positive effects produced by estrogen on allopregnanolone and β-END brain content.

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Section: Methodsmentioning

confidence: 99%

“…A blood specimen was drawn from each rat in heparinized and non-heparinized tubes, as previously reported [15, 18]. Blood collected in heparinized and non-heparinized tubes was centrifuged at 3,500 rpm for 10 min and plasma/serum was stored at –20°C until assay.…”

Section: Methodsmentioning

confidence: 99%

Progesterone and Medroxyprogesterone Acetate Effects on Central and Peripheral Allopregnanolone and Beta-Endorphin Levels

Bernardi¹,

Pluchino²,

Pieri³

et al. 2006

Neuroendocrinology

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“…In terms of the latter, it is clear that prolonged estrogen exposure decreases ␤END mRNA and peptide expression within the arcuate nucleus (380,382,383). However, ␤END peptide and mRNA analyses also show that a significant diurnal rhythm occurs within the ␤END neurons; ␤END expression is lowest in the afternoon, and this diurnal rhythm is only evident in the presence of estrogen (381,384,385). Hence, the arcuate ␤END neurons may be an additional site at which estrogen and circadian inputs are integrated before transmission to the GnRH neurons in the rat.…”

Section: June 1998 Estrogen Inputs To Gnrh Neurons 315mentioning

confidence: 99%

Multimodal Influence of Estrogen upon Gonadotropin-Releasing Hormone Neurons

1998

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“…For example, estrogen has been reported to either increase or decrease levels of the endogenous µ-/δ-ligand β-endorphin in the arcuate nucleus and in the POA [30, 31, 32, 33]. Maintenance of high plasma estrogen levels increases Met-enkephalin immunoreactivity in the medial preoptic nucleus [34].…”

Section: Discussionmentioning

confidence: 99%

Estrogen Modulation of Mu-Opioid Receptor-Stimulated [<sup>35</sup>S]-GTP-Gamma-S Binding in Female Rat Brain Visualized by in vitro Autoradiography

Acosta-Martínez

Etgen²

2002

Neuroendocrinology

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The µ-opioid receptor (OR) is involved in several aspects of female reproductive neuroendocrinology, such as the control of gonadotropin release and the display of lordosis behavior. Even though the neuroendocrine events modulated by µ-ORs are steroid hormone-dependent, few studies have shown how steroid hormones such as estrogen and/or progesterone can affect µ-OR function. Therefore, the present study investigated if in vivo estrogen or estrogen plus progesterone treatment of ovariectomized (OVX) rats affects µ-OR coupling to its G proteins. We used autoradiographic analysis of agonist-stimulated [³⁵S]-GTPγS binding, in which brain sections were incubated in the presence or absence of the µ-OR agonist [D-Ala², N-Me-Phe⁴, Gly²ol]-enkephalin (DAMGO). Film images were quantified using calibrated [¹⁴C] standards. Analysis was performed in steroid-responsive hypothalamic regions such as the medial preoptic area (mPOA) and the ventromedial nucleus of the hypothalamus, as well as in non-hypothalamic brain regions. Treatment with estrogen, alone or with progesterone, significantly increased DAMGO-stimulated [³⁵S]-GTPγS binding in the mPOA when compared to control OVX animals. In addition, estrogen increased µ-OR coupling in the caudate putamen. Steroid treatment had no effect on either basal or DAMGO-stimulated binding in the other brain regions examined. These findings suggest that estrogen modulates µ-OR function in a brain region-specific fashion. This could have important implications in terms of how these hormones synchronize reproductive behavior and gonadotropin release.

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Estrogens Modulate the Circadian Rhythm of Hypothalamic Beta-Endorphin Contents in Female Rats

Cited by 43 publications

References 15 publications

Progesterone and Medroxyprogesterone Acetate Effects on Central and Peripheral Allopregnanolone and Beta-Endorphin Levels

Progesterone and Medroxyprogesterone Acetate Effects on Central and Peripheral Allopregnanolone and Beta-Endorphin Levels

Multimodal Influence of Estrogen upon Gonadotropin-Releasing Hormone Neurons

Estrogen Modulation of Mu-Opioid Receptor-Stimulated [<sup>35</sup>S]-GTP-Gamma-S Binding in Female Rat Brain Visualized by in vitro Autoradiography

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