Influence of Blinding, Olfactory Bulbectomy and Pinealectomy on Plasma Prolactin Levels in the Neonatally Androgenized Female Rat

Gala, Richard R.; Haisenleder, Daniel J.; Pieper, David R.

doi:10.1159/000123509

Cited by 8 publications

(3 citation statements)

References 25 publications

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“…Therefore, the serum PRL level was depressed by pinealectomy in OVX-EP rats, in which the pineal gland has a stimulatory effect. In androgenized female rats subjected to ovariectomy and injection of estrogen, pinealectomy also resulted in a decrease in plasma PRL level (Gala et al 1983). Exogenous estrogen in these rats was demonstrated to induce the diurnal PRL pattern and seems to cause the pineal facilitation of PRL release as observed in OVX-EP rats.…”

Section: Discussionmentioning

confidence: 83%

Possible role of the pineal gland in pituitary prolactin secretion in female rats.

Minato¹,

Takahashi

Ikeno

et al. 1984

Tohoku J. Exp. Med.

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Wistar female rats housed under conditions of 12 hr dark/12 hr light were pinealectomized (PX) or underwent sham-operation (SO) 21 days after ovariectomy, on the 7th or on the 15-17 th day of pregnancy. Serum and pituitary prolactin (PRL) levels in ovariectomized (OVX) rats were determined 9 days after pinealectomy. In the case of OVX rats receiving estrogen and progesterone injections (OVX-EP), PRL levels were determined 48 hr after injection administered 7 day after pinealectomy. PRL levels in pregnant rats were determined on the 20th day of pregnancy and in postpartum rats, on the 3rd day following parturition. As compared with the SO control, pinealectomy resulted in a significant decrease in the serum PRL level in the OVX-EP rats but in a significant increase in that level in the OVX, pregnant and postpartum rats. In OVX-EP rats, exogenous estrogen raised the serum PRL level less in PX than in SO rats, probably because the pineal gland is closely related to the facilitation of PRL secretion by estrogen. The high estrogen level in OVX-EP rats seemed to trigger pineal stimulation of PRL release, but low estrogen levels in OVX and postpartum rats or markedly high levels of progesterone in pregnant rats on the 20th day are thought to cause pineal inhibition.prolactin ; pineal gland ; estrogen ; progesterone There have been no uniform conclusions about the role of the pineal gland in pituitary prolactin (PRL) secretion in the rat, because different experimental conditions have resulted in either inhibition or facilitation of PRL release by the pineal gland. We have previously studied the change in PRL secretion after pineal removal and administration of pineal bioactive substances, such as melatonin, serotonin and arginine vasotocin (AVT) and have demonstrated that antagonistic mechanisms of the pineal gland which affect pituitary PRL secretion

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Section: Discussionmentioning

confidence: 83%

Possible role of the pineal gland in pituitary prolactin secretion in female rats.

Minato¹,

Takahashi

Ikeno

et al. 1984

Tohoku J. Exp. Med.

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“…Moreover, increased melatonin levels and reduction of plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), T levels, testis weight, spermatozoa production, and sexual activity have been documented in animals rendered blind or exposed to a short photoperiod (44–48). These effects are prevented by pinealectomy (28, 45). Seasonal variations in luminosity influence melatonin secretion and some functions correlated not only in animals (28) but also in humans.…”

Section: Light Blindness and Hypothalamic–pituitary–gonadal Functionmentioning

confidence: 99%

Opposite Influence of Light and Blindness on Pituitary–Gonadal Function

et al. 2014

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Some environmental factors may influence the pituitary–gonadal function. Among these, light plays an important role in animals and in humans. The effect of light on the endocrine system is mediated by the pineal gland, through the modulation of melatonin secretion. In fact, melatonin secretion is stimulated by darkness and suppressed by light, thus its circadian rhythm peaks at night. Light plays a favorable action on the hypothalamic-pituitary axis likely inhibiting melatonin secretion, while the exogenous melatonin administration does not seem to impair the hormonal secretions of this axis. The basal and rhythmic pituitary–gonadal hormone secretions are regulated by a central clock gene and some independent clock genes in the peripheral tissues. Light is able to induce the expression of some of these genes, thus playing an important role in regulating the hormonal secretions of pituitary–gonadal axis and the sexual and reproductive function in animals and humans. The lack of light stimulus in blind subjects induces increase in plasma melatonin concentrations with a free-running rhythm of secretion, which impairs the hormonal secretions of pituitary–gonadal axis, causing disorders of reproductive processes in both sexes.

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“…In animals, light seems to improve pituitary-gonadal function through an inhibition of MT, whereas a reduction of photoperiod impairs pituitary-gonadal function through an activation of pineal gland secretion [48, 49, 50, 51, 52, 53]. Also in adult humans MT seems to influence gonadal function.…”

Section: Pituitary-gonadal Axismentioning

confidence: 99%

Endocrine Secretions under Abnormal Light-Dark Cycles and in the Blind

Bellastella

Pisano²,

Iorio³

et al. 1998

Horm Res Paediatr

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Both endogenous and exogenous factors are involved in regulation of endocrine secretions. Among the exogenous ones, light plays an important role both in animals and in humans. Pineal gland mediates light action on the endocrine system, by means of variations of melatonin (MT) secretion. Here we discuss about the influence of abnormal light-dark cycles and in particular of blindness on pineal and pituitary secretions and on those of correlated glands. MT secretion is usually inhibited by light: thus it reaches the highest levels at night. Exposure to short or long photoperiod causes variations in circadian or infradian MT rhythmicity. Blind patients can show higher daytime levels with a phase-advanced or phase-delayed circadian rhythm. Lack of light stimulus affects cortisol rhythm shifting the zenith of secretion and inducing a free-running rhythm. Blindness can abolish nocturnal growth hormone (GH) peak and impair the GH response to some stimuli; moreover it impairs the growth of affected patients. Light stimulus influences favorably gonadal function both in animals and in man. In animals, sexual activity and gonadal function decline during the seasons with reduced luminosity. A similar finding has been described in women living in a region with a strong seasonal contrast in luminosity. Blindness can impair luteinizing hormone, follicle-stimulating hormone, prolactin and testosterone secretion in prepubertal boys causing pubertal delay or more severe hypogonadism; it can affect pubertal development and fertility in women. Light can influence thyroid function in animals. Lack of light stimulus in blind man seems to cause different effects on thyroid function before and after puberty. Increase of free thyroid hormone levels has been found in prepubertal but not in adult blind patients, probably due to a resetting of the treshold for thyrotropin feedback suppression after puberty in these patients.

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Influence of Blinding, Olfactory Bulbectomy and Pinealectomy on Plasma Prolactin Levels in the Neonatally Androgenized Female Rat

Cited by 8 publications

References 25 publications

Possible role of the pineal gland in pituitary prolactin secretion in female rats.

Possible role of the pineal gland in pituitary prolactin secretion in female rats.

Opposite Influence of Light and Blindness on Pituitary–Gonadal Function

Endocrine Secretions under Abnormal Light-Dark Cycles and in the Blind

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