Effect of Gonadectomy and Gonadal Steroid Replacement on Pituitary and Plasma β-Endorphin Levels in the Rat

Peñalva, A; Locatelli, Vittorio; Panerai, Alberto E.; Genazzani, Alessandro; Ee, Müller

doi:10.1210/endo-111-4-1224

Cited by 117 publications

(55 citation statements)

References 22 publications

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“…Several investigators (42)(43)(44) have demonstrated that the effects of opioid-like peptides, in addition to being sex related, are also hormonally regulated. Our findings that the pretreatment of Con A-injected rats with opioid antagonists such as naloxone and naltrexone (45) completely blocked the hyperinsulinemia induced by this lectin (Figure 3) are consistent with the foregoing reports.…”

Section: Discussionmentioning

confidence: 99%

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

Francisco-DoPrado¹,

Zambelli²,

Lima³

et al. 1998

Braz J Med Biol Res

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The present study examines the effect of concanavalin A (Con A) on the blood insulin and glucose levels of rats. Male and female rats treated with Con A (62.5-500 µg/kg) for three days showed a dose-and time-dependent hyperinsulinemia that lasted more than 48 h. Male rats were more sensitive to Con A. Thus, 6 h after treatment with Con A the circulating insulin levels in male rats had increased by 85% (control: 10.2 ± 0.9 mU/l and Con A-treated: 18.8 ± 1 mU/l) compared to only 38% (control: 7.5 ± 0.2 mU/l; Con A-treated: 10.3 ± mU/l) in females. An identical response was seen after 12 h. Con A (250 µg/kg) produced time-dependent hypoglycemia in both sexes but more pronounced in males. There was no correlation between the hypoglycemia and hyperinsulinemia described above. The Con A-induced hyperinsulinemia in rats of both sexes was abolished in gonadectomized animals (intact males: +101 ± 17% vs orchiectomized males: -5 ± 3%; intact females: +86 ± 23% vs ovariectomized females: -18 ± 7.2%). Pretreating intact male and female rats with human chorionic gonadotropin also significantly inhibited the Con A-induced hyperinsulinemia. Estradiol (10 µg/kg, im) significantly blocked the Con A-induced increase in circulating insulin in male rats (101 ± 17% for controls vs 32 ± 5.3% for estradiol-treated animals, P<0.05) while testosterone (10 mg/kg, im) had no similar effect on intact female rats. Pretreating Con A-injected rats with opioid antagonists such as naloxone (1 mg/ kg, sc) and naltrexone (5 mg/kg, sc) blocked the hyperinsulinemia produced by the lectin in males (control: +101 ± 17% vs naloxonetreated: +5 ± 14%, or naltrexone-treated: -23 ± 4.5%) and females (control: +86 ± 23% vs naloxone-treated: +21 ± 20%, or naltrexonetreated: -18 ± 11%). These results demonstrate that Con A increases the levels of circulating insulin in rats and that this response is opioiddependent and hormonally regulated.

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Section: Discussionmentioning

confidence: 99%

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

Francisco-DoPrado¹,

Zambelli²,

Lima³

et al. 1998

Braz J Med Biol Res

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“…The fertile rats were housed together and were in the same estrous cycle stage, as indicated by the vaginal smears (taken every day). At the end of the treatment, each animal was killed by decapitation (on the same day), as previously described [11]and the following organs were taken: anterior pituitary, hypothalamus, hippocampus, adrenal glands. All organs were weighed .…”

Section: Methodsmentioning

confidence: 99%

“…All organs were weighed . A blood specimen was taken from each rat [11]. In each organ and blood sample allopregnanolone levels were measured within 40 days.…”

Section: Methodsmentioning

confidence: 99%

Effects of Estradiol and Raloxifene Analog on Brain, Adrenal and Serum Allopregnanolone Content in Fertile and Ovariectomized Female Rats

Genazzani¹,

Bernardi²,

Stomati³

et al. 2000

Neuroendocrinology

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Allopregnanolone is a neuroactive steroid synthesized in rat gonads, adrenal cortex, and central nervous system. It has been suggested that sex steroid hormones might influence allopregnanolone concentrations but no clear data have ever been reported. The aim of the present study was to investigate the effects of administration of 17β-estradiol (17β-E2), the raloxifene analog LY-117018 or their combination on allopregnanolone levels in fertile and ovariectomized (OVX) rats. Thirteen groups of 12 Wistar female rats each received either 17β-E2 (0.1 or 1 µg/day) or LY-117018 (25, 250, and 1,250 µg/day), or 17β-E2 1 µg/day plus LY-117018: 25, 250, and 1,250 µg/day for 14 days. The rats were then sacrificed and allopregnanolone content was assessed in the hypothalamus, hippocampus, pituitary, adrenals, and serum. Ovariectomy determined a significant decrease in allopregnanolone content in the hypothalamus, hippocampus, pituitary, and serum, while increasing it in the adrenals (p < 0.01). In OVX rats, the administration of either 17β-E2 or LY- 117018 restored ovariectomy-induced allopregnanolone changes. The administration of LY-117018 in addition to 17β-E2 to OVX animals suppressed the increase in allopregnanolone levels determined by 17β-E2 in the hippocampus, hypothalamus, and pituitary, but not in the adrenals and serum. In fertile rats, the administration of LY-117018 reproduced the effects of ovariectomy. This study shows that the raloxifene analog LY-117018 has an estrogen-like action on the central nervous system of OVX rats when administered alone, while it acts as an antiestrogen in the presence of 17β-E2, both in OVX animals treated with 17β-E2 and in fertile rats. A different effect was observed in the adrenal glands. The mechanism of action of this compound has still to be clarified.

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“…Estrogen receptors have been colocalized in ␤-END and NPY immunoreactive neurons (Morrell et al, 1985;Sar et al, 1990), and estradiol regulates the expression of both NPY and ␤-END in the arcuate nucleus of the hypothalamus (ARH) (Petraglia et al, 1982;Wardlaw et al, 1982;Wilcox and Roberts, 1985;Baskin et al, 1995;Priest and Roberts, 2000).…”

Section: Introductionmentioning

confidence: 99%

Estrogen-Induced μ-Opioid Receptor Internalization in the Medial Preoptic Nucleus Is Mediated via Neuropeptide Y-Y₁Receptor Activation in the Arcuate Nucleus of Female Rats

Mills¹,

Sohn²,

Micevych³

2004

J. Neurosci.

106

152

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Effect of Gonadectomy and Gonadal Steroid Replacement on Pituitary and Plasma β-Endorphin Levels in the Rat

Cited by 117 publications

References 22 publications

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

Effects of Estradiol and Raloxifene Analog on Brain, Adrenal and Serum Allopregnanolone Content in Fertile and Ovariectomized Female Rats

Estrogen-Induced μ-Opioid Receptor Internalization in the Medial Preoptic Nucleus Is Mediated via Neuropeptide Y-Y₁Receptor Activation in the Arcuate Nucleus of Female Rats

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Effect of Gonadectomy and Gonadal Steroid Replacement on Pituitary and Plasma β-Endorphin Levels in the Rat

Cited by 117 publications

References 22 publications

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

The hyperinsulinemia produced by concanavalin A in rats is opioid-dependent and hormonally regulated

Effects of Estradiol and Raloxifene Analog on Brain, Adrenal and Serum Allopregnanolone Content in Fertile and Ovariectomized Female Rats

Estrogen-Induced μ-Opioid Receptor Internalization in the Medial Preoptic Nucleus Is Mediated via Neuropeptide Y-Y1Receptor Activation in the Arcuate Nucleus of Female Rats

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Estrogen-Induced μ-Opioid Receptor Internalization in the Medial Preoptic Nucleus Is Mediated via Neuropeptide Y-Y₁Receptor Activation in the Arcuate Nucleus of Female Rats