Some Endocrine Effects of the Pineal Gland and Melatonin with Special Reference to Reproduction

Mess, B; Trentini, G. P.; Rúzsás, C; Gaetani, C. F. De

doi:10.1016/s0079-6123(08)62938-6

Cited by 14 publications

(5 citation statements)

References 54 publications

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“…Possibly more rats with altered LH secretion would have appeared if the postsurgical time was increased. Similar changes in LH secretion were observed by others in pinea lectomized rats showing restored cyclicity after periods of experimentally induced anovulation [19]. Furthermore, the LH surge is attenuated and delayed, as after pinealectomy, in rats exposed to continuous illumination [10,18].…”

Section: Discussionsupporting

confidence: 84%

Melatonin and the Influence of the Pineal Gland on Timing of the LH Surge in Rats

Walker

McCamant

Timiras³

1982

Neuroendocrinology

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The purpose of this study was to determine if the temporal relationship between the LH surge and the photo-period is influenced by melatonin and the pineal gland in the rat. The timing of melatonin synthesis and of preovulatory LH release is reciprocally related; and since melatonin blocks LH secretion, it was hypothesized that the pineal ‘hormone’ contributes normally to termination of the LH surge. To test this hypothesis, we examined the temporal pattern of phasic LH secretion after altering pineal activity in rats with regular estrous cycles. Termination of the LH surge was delayed in rats exposed to a photophase acutely prolonged into the night of proestrus; a treatment which delays melatonin synthesis. On the other hand, the LH surge terminated normally despite extended light exposure, if the rats were injected with melatonin at 19.00 h, when the dark phase usually begins. Melatonin injections during the standard photophase, i.e. at 13.00 or 17.00 h, blocked or prematurely terminated the LH surge, respectively. However, these effects probably do not represent a physiological function of melatonin, since its synthesis does not accelerate normally until after dark. 5 out of 14 pinealectomized rats showed altered patterns of preovulatory LH secretion 2 months after surgery. Since melatonin has been reported to block serotonin receptors, and serotonin stimulates phasic secretion of LH, we tested the ability of quipazine, a serotonin receptor agonist, to antagonize the inhibitory effect of melatonin on the LH surge. Quipazine given at 15.30 h blocked the inhibitory effect of melatonin administered at 16.00 h. The serotonin agonist partially restored LH levels in proestrous rats when it was given 30 min after melatonin. Therefore, the inhibitory effect of melatonin on phasic secretion of LH may result from an action upon serotonin-containing neurons. These findings taken together suggest that the pineal gland, ostensibly through the action of melatonin, contributes to termination of phasic LH secretion and thereby participates in entrainment of the LH surge to the photoperiod in the female rat.

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Section: Discussionsupporting

confidence: 84%

Melatonin and the Influence of the Pineal Gland on Timing of the LH Surge in Rats

Walker

McCamant

Timiras³

1982

Neuroendocrinology

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“…It has been maintained that this gland exerts fundamental control over the endocrine system (Mess et al, 1979) as well as the immune (Rella and Lapin, 1976) and the nervous system (Romijn, 1978). Reciprocally, the pineal gland is affected by both, exogenous factors, particularly light (Reiter, 1978), and a number of endogenous factors, namely several hormones (Cardinali and Vacas, 1976) and sympathetic nervous inputs (Ueck, 1979).…”

Section: Introductionmentioning

confidence: 99%

Urinary melatonin levels in human breast cancer patients

Bartsch

Jain

et al. 1981

J. Neural Transmission

113

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Urinary melatonin levels were measured in 10 postmenopausal Indian women suffering from advanced stages of breast cancer and in 9 well-matched women with non-endocrine complaints, mostly uterovaginal prolapse. Urines of each patient were collected over a period of 2-3 days in four 4-hourly intervals from 6 a.m. to 10 p.m. and one 8-hourly interval from 10 p.m. to 6 a.m. Serum LH, FSH, prolactin, estradiol and cortisol levels at 11 a.m. were determined as well as estrogen and progesterone receptors of the breast tumors. It was found that 24 hour urinary melatonin excretion in cancer patients was on the average 31% decreased as compared to the controls. This change was accompanied by a 33% increase in serum cortisol levels in the cancer patients. The melatonin excretion patterns of the cancer patients were not synchronized as compared to synchronized patterns of the controls. The number of tumors tested for steroid receptors does not yet allow to conclude if melatonin is different in patients with or without hormone-dependent tumors. The data suggest that pineal melatonin secretion may be modified in quantity as well as rhythmicity in breast cancer patients.

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“…Melatonin, the gland's predominant hormone, has been primarily designated for this effect [24,25,28,32]. In the male rat melatonin has been found to decrease the secretion ofgonadotropins [6,13,17,21] and to modify the synthesis [22], metabolism [7,14], and activity [1,4] of gonadal androgens.…”

Section: Introductionmentioning

confidence: 99%

Role of the pineal gland in the regulation of prostatic androgen receptors in pubertal and mature rats

Moêller

Rödl

et al. 1983

Res. Exp. Med.

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The effects of exposure to continuous light, continuous darkness, and administration of melatonin on prostatic androgen receptors in relation to pubertal development in rats were examined. Darkness produced dissimilar results between the pubertal and adult groups. Whereas the prostate weight in the pubertal group remained unaltered, it increased in the adult group. In the pubertal group exposed to darkness, plasma melatonin increased significantly, and androgen receptors declined, whereas in the adult group these receptors rose significantly with a simultaneous increment of melatonin concentration in plasma. Exposure to continuous light did not produce any effective alterations in the parameters examined. The afternoon melatonin administration showed trends similar to those seen in animals exposed to darkness. The results indicate that exposure to darkness or administration of melatonin both have age-dependent effects on prostatic androgen receptors. Exposure to darkness may interfere with the process of sexual maturation in the pubertal animal as a result of increased melatonin production.

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Some Endocrine Effects of the Pineal Gland and Melatonin with Special Reference to Reproduction

Cited by 14 publications

References 54 publications

Melatonin and the Influence of the Pineal Gland on Timing of the LH Surge in Rats

Melatonin and the Influence of the Pineal Gland on Timing of the LH Surge in Rats

Urinary melatonin levels in human breast cancer patients

Role of the pineal gland in the regulation of prostatic androgen receptors in pubertal and mature rats

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