Changes in pituitary prolactin content in rats at mid-pseudopregnancy.

SUMMARY The effects of constant light, constant darkness and diurnal lighting, in combination with pinealectomy or sham-pinealectomy, on pituitary and plasma concentrations of radioimmunoassayable prolactin were investigated in 8-week-old male and virgin female rats. Two to three days after operation random groups of pinealectomized and sham-pinealectomized animals of the same sex were placed together in either continous light, continuous darkness or diurnal light, and killed 21 days later. Compared with sham-operated diurnally-illuminated controls, constant darkness caused a decrease in pituitary prolactin content and a rise in plasma prolactin levels. Pinealectomy or constant illumination reversed the effect of constant darkness, resulting in an increase in pituitary prolactin content and a fall in plasma prolactin levels when compared with sham-operated diurnally-illuminated controls. Electron microscopy of lactotrophic cells of the sham-pinealectomized animals exposed to constant darkness revealed few cytoplasmic granules, whereas these cells in the sham-pinealectomized animals exposed to constant light contained abundant granules; compared with the former groups, lactotrophic cells of sham-pinealectomized rats exposed to diurnal lighting revealed an intermediate degree of granulation.

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Increased dopaminergic inhibition of prolactin in the hypoprolactinaemic IPL nude rat

Journal of Endocrinology ◽

10.1677/joe.0.1070325 ◽

1985 ◽

Vol 107 (3) ◽

pp. 325-329 ◽

Cited By ~ 4

Author(s):

H. Cohen ◽

I. Sabbagh ◽

P. Guillaumot ◽

J. Bertrand

Keyword(s):

Adult Male ◽

Physiological Saline ◽

Prolactin Secretion ◽

Male Rats ◽

Saline Control ◽

Plasma Prolactin ◽

Synthesis Inhibitor ◽

Nude Rat ◽

Prolactin Content ◽

Pituitary Prolactin

ABSTRACT In this study, aimed at investigating whether dopaminergic regulation of prolactin could be implicated in the hypoprolactinaemia observed in the IPL nude rat, dopaminergic inhibition of prolactin was suppressed using a catecholamine synthesis inhibitor α-methyltyrosine (MT) and a dopaminergic antagonist sulpiride. Adult male rats (IPL nude and normal) were injected through implanted atrial cannulae with either MT (250 mg/kg) or physiological saline (control). Rats were decapitated 2 h after the injection. Plasma prolactin levels, compared with basal values, increased by 15·6 ± 1·9 (s.e.m.)- and 5·89 ± 0·6-fold in IPL nude and normal rats respectively. This difference was highly significant. The pituitary prolactin content was decreased in both groups. In a second experiment, adult male IPL nude or normal rats were injected with either sulpiride (1 mg/kg) or saline and decapitated 2, 4, 8, 12, 14 and 24 h later. Plasma prolactin levels, compared with basal values, were increased in rats injected with sulpiride by 9·2 ± 1·8 and 3·4 ± 0·7-fold in IPL nude and normal rats respectively. The pituitary prolactin content was reduced more in IPL nude than in normal sulpiride-injected rats. These data suggest that prolactin secretion, as well as synthesis, is under an increased dopaminergic inhibition in the male IPL nude rat. J. Endocr. (1985) 107, 325–329

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IN-VIVO ASSAY FOR HYPOTHALAMIC PROLACTIN-INHIBITING FACTOR

Journal of Endocrinology ◽

10.1677/joe.0.0460237 ◽

1970 ◽

Vol 46 (2) ◽

pp. 237-241 ◽

Cited By ~ 2

Author(s):

A. DANON ◽

S. DIKSTEIN ◽

F. G. SULMAN

Keyword(s):

Cerebral Cortex ◽

Adult Male ◽

Male Rats ◽

Assay Method ◽

Rat Hypothalamus ◽

Inhibiting Factor ◽

Prolactin Content ◽

Pituitary Prolactin ◽

Dose Dependent

SUMMARY Treatment of intact adult male rats with 10 mg. perphenazine (Trilafon)/kg. resulted in a decrease in the prolactin content of the pituitary within 1 hr. This decrease was probably due to suppression of the hypothalamic prolactin-inhibiting factor (PIF). Subsequent intracarotid infusion of neutralized acid extracts of rat hypothalamus restored the pituitary prolactin content. This effect was dose-dependent within a range of ½-2 hypothalami. Infusion of extracts of cerebral cortex failed to increase pituitary prolactin. The response to the hypothalamic extracts is considered to be specific for PIF and is proposed as an assay method for PIF.

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Effects of Intrahypothalamic Implants of Reserpine on Lactation and Pituitary Prolactin Content in the Rabbit.

Experimental Biology and Medicine ◽

10.3181/00379727-113-28546 ◽

1963 ◽

Vol 113 (4) ◽

pp. 967-969 ◽

Cited By ~ 15

Author(s):

S. Kanematsu ◽

C. H. Sawyer

Keyword(s):

Prolactin Content ◽

Pituitary Prolactin

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Effects of ovariectomy and of oestrogen administration on the decrease in pituitary prolactin content which occurs on the afternoon of pro-oestrus in the rat

Cellular and Molecular Life Sciences ◽

10.1007/bf02286942 ◽

1971 ◽

Vol 27 (10) ◽

pp. 1221-1222

Author(s):

A. Yokoyama ◽

H. Tomogane ◽

K. Ôta

Keyword(s):

Prolactin Content ◽

Pituitary Prolactin

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Perinatal Glucocorticoid Treatment Disrupts the Hypothalamo-Lactotroph Axis in Adult Female, But Not Male, Rats

Endocrinology ◽

10.1210/en.2005-1496 ◽

2006 ◽

Vol 147 (4) ◽

pp. 1904-1915 ◽

Cited By ~ 18

Author(s):

S. McArthur ◽

Z.-L. Siddique ◽

H. C. Christian ◽

G. Capone ◽

E. Theogaraj ◽

...

Keyword(s):

Drinking Water ◽

Sex Differences ◽

Cell Size ◽

Dopaminergic Neurons ◽

Arcuate Nucleus ◽

Male Rats ◽

Cell Numbers ◽

Th Cell ◽

Prolactin Content ◽

Pituitary Prolactin

This study aimed to test the hypothesis that the tuberoinfundibular dopaminergic neurons of the arcuate nucleus and/or the lactotroph cells of the anterior pituitary gland are key targets for the programming effects of perinatal glucocorticoids (GCs). Dexamethasone was administered noninvasively to fetal or neonatal rats via the mothers’ drinking water (1 μg/ml) on embryonic d 16–19 or neonatal d 1–7, and control animals received normal drinking water. At 68 d of age, the numbers of tyrosine hydroxylase-positive (TH+) cells in the arcuate nucleus and morphometric parameters of pituitary lactotrophs were analyzed. In control animals, striking sex differences in TH+ cell numbers, lactotroph cell size, and pituitary prolactin content were observed. Both pre- and neonatal GC treatment regimens were without effect in adult male rats, but in females, the overriding effect was to abolish the sex differences by reducing arcuate TH+ cell numbers (pre- and neonatal treatments) and reducing lactotroph cell size and pituitary prolactin content (prenatal treatment only) without changing lactotroph cell numbers. Changes in circulating prolactin levels represented a net effect of hypothalamic and pituitary alterations that exhibited independent critical windows of susceptibility to perinatal GC treatments. The dopaminergic neurons of the hypothalamic periventricular nucleus and the pituitary somatotroph populations were not significantly affected by either treatment regimen in either sex. These data show that the adult female hypothalamo-lactotroph axis is profoundly affected by perinatal exposure to GCs, which disrupts the tonic inhibitory tuberoinfundibular dopaminergic pathway and changes lactotroph morphology and prolactin levels in the pituitary and circulation. These findings provide new evidence for a long-term disruption in prolactin-dependent homeostasis in females, but not males, after inappropriate GC exposure in perinatal life.

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Photoperiodic control of the development of the LHRH neurosecretory system of European starlings (Sturnus vulgaris) during puberty and the onset of photorefractoriness

Journal of Endocrinology ◽

10.1677/joe.0.1220255 ◽

1989 ◽

Vol 122 (1) ◽

pp. 255-268 ◽

Cited By ~ 45

Author(s):

A. R. Goldsmith ◽

W. E. Ivings ◽

A. S. Pearce-Kelly ◽

D. M. Parry ◽

G. Plowman ◽

...

Keyword(s):

Median Eminence ◽

Sexual Maturation ◽

Staining Intensity ◽

Neurosecretory System ◽

Inhibitory Influence ◽

European Starlings ◽

Testicular Regression ◽

Lhrh Release ◽

Prolactin Content ◽

Pituitary Prolactin

ABSTRACT The development of the reproductive system was studied in juvenile starlings during the acquisition of photosensitivity, the attainment of sexual maturation after photostimulation and the subsequent onset of photorefractoriness, using immunohistochemistry for LHRH and radioimmunoassay measurements of hypothalamic, pituitary and plasma hormone concentrations. The first stage of sexual development induced by exposure of photorefractory immature starlings to short days (8 h light:16 h darkness; 8L:16D) was characterized by a decrease in pituitary prolactin content within 1 week and an increase in hypothalamic LHRH content, in the size of the LHRH perikarya and in the intensity of immunostaining in the median eminence in 4–6 weeks. Sexual maturation occurring after exposure to long days (18L:6D) was associated with further increases in LHRH content and cell size, and increases in LH and prolactin concentrations. During testicular regression, LHRH perikarya were reduced in size and staining intensity but LHRH immunostaining in the median eminence and content in the hypothalamus remained high until gonadal regression was almost complete. Prolactin levels were maximal during testicular regression. These results suggest that gonadal regression is initiated by a reduction in LHRH synthesis and possibly, in addition, an external inhibitory influence on LHRH release. Hypothalamic LHRH content eventually declined and LHRH immunostaining in the median eminence was much reduced in fully photorefractory starlings maintained under long days. Journal of Endocrinology (1989) 122, 255–268

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