Ovarian steroids block the isoproterenol-induced elevation of pineal melatonin production in the female rat

Moujir, Fatima; Bordon, R; Santana, C.; Abreu, Pedro; Hernández, Guadalberto; Alonso, Rafael

doi:10.1016/0304-3940(90)90743-s

Cited by 33 publications

(16 citation statements)

References 19 publications

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“…Ovariectomy has been generally reported to increase the pineal or serum concentrations (or both) of melatonin in rats (12,15,16). Administration of estrogen decreases isoproterenol-induced increases in pineal melatonin in ovariectomized rats (11,21). The present study supports these past reports, which revealed that ovariectomy in rats increases melatonin production and that estrogen replacement reverses the melatonin concentrations to preovariectomy values.…”

Section: Discussionsupporting

confidence: 90%

Melatonin secretion from organ-cultured pineal glands of rats: modulation by gonadectomy and gonadotropin-releasing hormone agonist administration

Ishizuka

Fusama²,

Hirai³

et al. 2000

European Journal of Endocrinology

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The objective of the study was to evaluate the effect of pretreatments such as gonadectomy in male and female rats, and gonadotropin-releasing hormone agonist (GnRHa) administration in female rats, on levels of secretion of melatonin, using an organ culture of pineal glands. Gonadectomy 2 weeks before the animal was killed increased the amount of melatonin secreted into the medium by the pineal glands of female rats but not of male rats. The increase in in vitro melatonin secretion after ovariectomy in female rats was prevented by estrogen replacement. Ovariectomy 3 and 4 weeks before death also significantly increased the amount of melatonin secretion. Administration of GnRHa 2 weeks before decapitation significantly decreased serum estradiol concentrations and significantly increased melatonin secretion by the pineal glands of female rat. GnRHa administration 3 or 4 weeks before decapitation also significantly decreased serum estradiol concentrations, but did not increase pineal secretion of melatonin. The results indicate that ovariectomy increases melatonin secretion from organ-cultured pineal glands and that this increase is suppressed by estrogen in adult female rats. In contrast, orchiectomy in male rats does not influence in vitro secretion of melatonin. These results suggest that the GnRH-gonadotropin system may participate in the regulation of pineal melatonin secretion in adult female rats.

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Section: Discussionsupporting

confidence: 90%

Melatonin secretion from organ-cultured pineal glands of rats: modulation by gonadectomy and gonadotropin-releasing hormone agonist administration

Ishizuka

Fusama²,

Hirai³

et al. 2000

European Journal of Endocrinology

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“…Besides differences in experimental models, the most consistent picture indicates that, in rodents, nocturnal melatonin synthesis and secretion is reduced at the time of proestrous night, apparently coinciding with the rise of estradiol preceding ovulation [11, 12]. Acute treatment of ovariectomized rats with sex steroids blocks the ISO-induced rise of pineal and serum melatonin levels [13, 27]. In addition, in peripubertal rats, ovariectomy has been shown to induce elevations of pineal melatonin levels, NAT activity, and AC activity several weeks after removal of the ovaries [10, 28], effects that were prevented by long-term treatment with estradiol benzoate.…”

Section: Discussionmentioning

confidence: 99%

“…In female rats, both melatonin synthesis and release are reduced during the night of proestrus [11, 12]. Treatment with ovarian hormones block the β-adrenoceptor-induced rise of pineal melatonin in ovariectomized rats in vivo [13], and regulate the sensitivity of pinealocytes to in vitro adrenergic stimulation [14]. In the present study, we have investigated whether direct exposure of female rat pinealocytes to physiological estrogen concentrations affects melatonin synthesis and release in response to adrenergic stimulation.…”

Section: Introductionmentioning

confidence: 99%

Estrogen Modulates α<sub>1</sub>/β-Adrenoceptor- Induced Signaling and Melatonin Production in Female Rat Pinealocytes

et al. 2001

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Nocturnal rise in pineal melatonin output is due to the night-induced acceleration of noradrenergic transmission and α₁- and β-adrenoceptor activation. In addition, in female animals, cyclic oscillations in circulating levels of sex steroid hormones are accompanied by changes in the rate of pineal melatonin secretion. To investigate whether estrogen directly affects pineal adrenoceptor responsiveness, pinealocytes from 21-day-old ovariectomized rats were exposed to physiological concentrations of 17β-estradiol (17β-E₂) and treated with noradrenergic agonists. Direct exposure to 17β-E₂ reduced α₁/β-adrenoceptor-induced stimulation of melatonin synthesis and release. This effect was mediated by an estrogen-dependent inhibition of both β-adrenoceptor-induced accumulation of cAMP and α₁-adrenoceptor-induced phosphoinositide hydrolysis. Furthermore, estrogen reduced transient Ca²⁺ signals elicited in single pinealocytes by α₁-adrenoceptor activation or by potassium-induced depolarization. In the case of β-adrenoceptor responsiveness, neither forskolin- nor cholera toxin-induced accumulation of cAMP were affected by previous exposure to 17β-E₂. This indicates that estrogen effects must be exerted upstream from adenylylcyclase activation, and independent of modifications in G protein expression, therefore suggesting changes in either adrenoceptor expression or receptor-effector coupling mechanisms. Since estrogen effects upon adrenoceptor responsiveness in pineal cells was not mimicked by 17β-E₂ coupled to bovine serum albumin and showed a latency of 48 h, this effect could be compatible with a genomic action mechanism. This is also consistent with the presence of two estrogen receptor proteins, α- and β-subtypes, in female rat pinealocytes under the present experimental conditions.

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“…In general, testosterone exhibits stimulatory effects and castration reduces cAMP concentrations (Karasek et al, 1978), AA-NAT activity (Rudeen and Reiter, 1980), and MEL synthesis . In contrast, estradiol displays an inhibitory effect on the ␣ 1 /␤ 1 -AR-induced increase in cAMP and Ca 2ϩ i levels, AA-NAT activity, and MEL production in female rats, while ovariectomy leads to a significant increase in the cAMP/AA-NAT/ MEL pathway (Moujir et al, 1990a;Okatani et al, 1997Okatani et al, , 1998Hayashi and Okatani, 1999;Ishizuka et al, 2000;Hernandez-Diaz et al, 2001). Similarly, an increase in nocturnal MEL secretion (associated with an increase in AA-NAT but not HIOMT activity) was observed during menopause in relation to the existence of a low estrogen environment in the rat and human (Okatani et al, 2000).…”

mentioning

confidence: 99%

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

Simonneaux

Ribelayga

2003

Pharmacological Reviews

615

486

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Ovarian steroids block the isoproterenol-induced elevation of pineal melatonin production in the female rat

Cited by 33 publications

References 19 publications

Melatonin secretion from organ-cultured pineal glands of rats: modulation by gonadectomy and gonadotropin-releasing hormone agonist administration

Melatonin secretion from organ-cultured pineal glands of rats: modulation by gonadectomy and gonadotropin-releasing hormone agonist administration

Estrogen Modulates α<sub>1</sub>/β-Adrenoceptor- Induced Signaling and Melatonin Production in Female Rat Pinealocytes

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

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