A possible dual regulation of prolactin release by the serotoninergic system in rats at pro-oestrus and during late pregnancy: role of ovarian hormones

1987 ◽  
Vol 112 (3) ◽  
pp. 367-374 ◽  
Author(s):  
G. A. Jahn ◽  
R. P. Deis
Keyword(s):  
Serotonin Receptor ◽  
Late Pregnancy ◽  
Inhibitory Effect ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Serotoninergic System ◽  
Serum Concentrations ◽  
Prolactin Release ◽  
Treatment Administration ◽  
Significant Release

ABSTRACT The effect of para-chlorophenylalanine (pCPA), an inhibitor of serotonin synthesis, on prolactin release was studied in rats on the day of pro-oestrus and at the end of pregnancy (day 19). The surges of prolactin normally seen in the afternoon of pro-oestrus in intact rats and in rats ovariectomized on dioestrous day 2 and primed with oestrogen were significantly inhibited by pCPA treatment. Administration of 5-hydroxy-tryptophan reversed the inhibitory action of pCPA on prolactin release. Treatment with progesterone also completely reversed the inhibitory effect of pCPA on prolactin release in pro-oestrous rats and partially reversed it in ovariectomized oestrogen-treated rats. Ovariectomy on day 19 of pregnancy induced a significant release of prolactin 12 and 24 h later. Administration of pCPA on day 18 of pregnancy produced a marked increase in serum concentrations of prolactin on days 19 and 20 in rats left intact or ovariectomized on day 19. Administration of 5-hydroxy-tryptophan significantly reversed this stimulatory effect of pCPA on prolactin release but did not modify the release of prolactin induced by ovariectomy. Methiothepin (1-[10,11-dihydro-8-(methylthio) <b,f> thiepin-10,41]-4-methylpiperazine maleate), a serotonin receptor blocker, also induced a significant increase in serum concentrations of prolactin on day 20 of pregnancy in rats left intact or ovariectomized on day 19. These results suggest the existence of different serotoninergic actions in the regulation of prolactin release at pro-oestrus and in late pregnancy. Serotonin facilitates the surges of serum prolactin released at pro-oestrus and in ovariectomized rats treated with oestrogen; progesterone enhances this effect. On the other hand, during late pregnancy, when progesterone tonically inhibits prolactin release, serotonin inhibits the release of prolactin. J. Endocr. (1987) 112, 367–374

A central action of α-melanocyte-stimulating hormone on serum levels of LH and prolactin in rats

1990 ◽  
Vol 124 (1) ◽  
pp. 127-132 ◽  
Author(s):  
T. Scimonelli ◽  
M. E. Celis
Keyword(s):  
Dopaminergic System ◽  
Single Injection ◽  
Serum Levels ◽  
Inhibitory Effect ◽  
Ovariectomized Rats ◽  
Serum Concentrations ◽  
Prolactin Release ◽  
Blood Samples ◽  
Melanocyte Stimulating Hormone ◽  
Tuberoinfundibular Dopaminergic System

ABSTRACT We have investigated the effect of administration of α-MSH into the median eminence (ME) of rats on the release of LH and prolactin. Continuous infusion of α-MSH (0·5 μg/h) into the ME from the afternoon of the second day of dioestrus and over the 24 h of pro-oestrus inhibited the preovulatory LH and prolactin surge and the occurrence of ovulation. This inhibitory effect on LH and prolactin release was also observed in chronically ovariectomized rats given a single injection of α-MSH (1 μg/μl per rat) into the ME (blood samples were collected 0,20,60,90,105 and 120 min after injection). The intraperitoneal injection of the dopamine receptor blocker, haloperidol (2 mg/kg), 30 min before the injection of α-MSH into the ME prevented the inhibitory effect of α-MSH on the release of LH and prolactin. These results suggest that hypothalamic α-MSH might be involved in the regulation of LH and prolactin release via the tuberoinfundibular dopaminergic system and that this system also modifies the serum concentrations of α-MSH. Journal of Endocrinology (1990) 124, 127–132

FAILURE OF MELATONIN TO INCREASE SERUM PROLACTIN LEVELS IN OVARIECTOMIZED RATS SUBJECTED TO SUPERIOR CERVICAL GANGLIONECTOMY OR PINEALECTOMY

1979 ◽  
Vol 82 (2) ◽  
pp. 315-319 ◽  
Author(s):  
D. P. CARDINALI ◽  
MARÍA R. FAIGÓN ◽  
P. SCACCHI ◽  
J. MOGUILEVSKY
Keyword(s):  
Pineal Gland ◽  
Steroid Treatment ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Prolactin Release ◽  
Intracranial Surgery ◽  
Superior Cervical Ganglionectomy ◽  
Significant Depression

SUMMARY The effects of melatonin on serum prolactin levels were examined in ovariectomized rats primed with oestradiol and progesterone, and subjected to bilateral superior cervical ganglionectomy or pinealectomy. Ganglionectomy resulted in a significant depression of the serum prolactin concentration, as well as in impairment of the prolactin release evoked by administration of steroid. Treatment with melatonin increased serum prolactin in control but not in ganglionectomized rats. Injection of melatonin potentiated the steroid-induced release of prolactin in control rats; this effect of melatonin was not detected in ganglionectomized rats. Pinealectomy did not affect basal prolactin levels, nor impair the release of prolactin evoked by steroid treatment; however, it was effective in blocking the melatonin-induced release of prolactin in vehicletreated rats, as well as the potentiation of steroid-induced prolactin release by melatonin. Intracranial surgery by itself increased prolactin release. These results suggest that systemically administered melatonin needs an intact pineal gland to augment serum prolactin levels.

Serum concentrations of testosterone throughout pregnancy in rats

1982 ◽  
Vol 94 (1) ◽  
pp. 21-27 ◽  
Author(s):  
R. S. Bridges ◽  
R. B. Todd ◽  
C. M. Logue
Keyword(s):  
Post Partum ◽  
Late Pregnancy ◽  
Serum Testosterone ◽  
Serum Levels ◽  
Diurnal Variations ◽  
Serum Prolactin ◽  
Serum Concentrations ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
Microcolumn Chromatography

Testosterone concentrations in serum of rats bled throughout pregnancy and post partum were measured using Celite microcolumn chromatography and a radioimmunoassay for testosterone. Mean serum levels of testosterone ranged from about 170 to 340 pmol/l during the first 10 days of pregnancy. Significant increases in concentrations of testosterone in serum of pregnant rats were found on days 12, 15 and 18 of gestation. The highest testosterone concentrations occurred on days 18 and 20 of pregnancy when mean levels were 3228 and 3685 pmol/l respectively. Testosterone levels declined before parturition on day 22 (mean = 1449 pmol/l and declined further after parturition (mean = 315 pmol/l). In order to determine whether serum testosterone concentrations varied during the day in the pregnant rat, samples were collected at 6-h intervals on days 6–7 and 14–15 of gestation. Diurnal variations in serum testosterone concentrations were not evident during early or late pregnancy, unlike the rhythmic changes in serum prolactin levels found at these times during early pregnancy. The possible sources of the increased titres of serum testosterone during the second part of gestation in rats are discussed.

INHIBITORY EFFECT OF PROGESTERONE ON THE LACTOGENIC AND ABORTIVE ACTION OF PROSTAGLANDIN F2α

1975 ◽  
Vol 66 (1) ◽  
pp. 21-29 ◽  
Author(s):  
NELIA T. VERMOUTH ◽  
R. P. DEIS
Keyword(s):  
Single Dose ◽  
Plasma Concentration ◽  
Prostaglandin F2α ◽  
Inhibitory Effect ◽  
Induced Abortion ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Pregnant Rats ◽  
Unilateral Ovariectomy ◽  
Prostaglandin F

SUMMARY The effect of ovariectomy, progesterone and prolactin treatment on the action of prostaglandin F2α (PGF2α) was determined in pregnant rats. PGF2α (150 μg × 2) injected i.p. on day 19 or 18 of pregnancy induced lactogenesis about 25 h later and abortion on days 20 and 21 of pregnancy. Treatment with PGF2α (100 μg × 2 or 50 μg × 2) on day 19 induced lactogenesis around 22 or 38 h later, respectively, and abortion on day 21. PGF2α treatment on day 17 was less effective. Unilateral ovariectomy on day 17 of pregnancy induced lactogenesis 32 h later but not abortion. PGF2α (150 μg × 2) given on the day of surgery advanced lactogenesis 12 h and rats aborted on day 19. Bilateral ovariectomy on day 17 induced abortion between days 20 to 21, but if a single dose of PGF2α (300 μg) was injected on day 18, all the ovariectomized rats aborted on day 19. Progesterone (10 mg) injected into rats treated with PGF2α (150 μg × 2) on day 18, prevented abortion and delayed lactogenesis. Prolactin (1 mg × 4) treatment delayed only abortion. Serum prolactin levels were significantly higher 12 h after the last dose of PGF2α (150 μg × 2) in rats treated on days 17, 18 or 19 of pregnancy. Pretreatment with progesterone prevented the rise in prolactin concentration. These results suggest that the lactogenic and abortive action of PGF2α may be dependent on the uterine and plasma concentration of progesterone.

PROLACTIN RELEASE AND LACTOGENESIS AFTER OVARIECTOMY IN PREGNANT RATS: EFFECT OF OVARIAN HORMONES

1974 ◽  
Vol 63 (1) ◽  
pp. 13-20 ◽  
Author(s):  
NELIA T. VERMOUTH ◽  
R. P. DEIS
Keyword(s):  
Ovarian Hormones ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Rapid Rise ◽  
Prolactin Release ◽  
Pregnant Rats ◽  
Blood Concentrations ◽  
Oestrogen Treatment ◽  
Progesterone Treatment

SUMMARY Ovariectomy of rats on day 19 of pregnancy induced a rapid rise in serum prolactin. Levels were significantly increased 4 h after removal of the ovaries and continued to rise up to 24 h. A transient fall occurred at 32 h, but serum prolactin concentration was still raised after 36, 48 and 58 h. Similar increases of serum prolactin occurred after ovariectomy on days 17 and 18 of pregnancy. Lactogenesis occurred 24·8 or 28·2 h after ovariectomy on days 19 or 17–18 of pregnancy respectively. Rats ovariectomized on day 17 or 18 delivered on day 21 and rats ovariectomized on day 19 delivered on day 22 of pregnancy. Ovariectomy impaired parturition in all groups. Treatment with oestrogen immediately after the operation did not prevent the rise in serum prolactin levels 4, 8 and 12 h after ovariectomy, but 24 h after ovariectomy, prolactin values were not significantly different from those in sham-operated control rats. When oestrogen was injected 12 h after ovariectomy, serum prolactin was markedly increased 12 h later. Lactogenesis occurred about 22·9 h after oestrogen treatment and all animals delivered on day 21 of pregnancy. Progesterone treatment prevented the rise in prolactin levels observed 4 and 8 h after ovariectomy, but at 12 h levels had risen and were similar to those observed in untreated ovariectomized rats. Progesterone prevented lactogenesis for 14 h (around 37.5 h after ovariectomy) and induced a delay in the onset of parturition. The results indicate that the decrease of progesterone in the blood after ovariectomy in pregnant rats may induce a release of prolactin and lactogenesis. Oestrogen seems to be effective in raising prolactin levels at low blood concentrations of progesterone.

Evidence that prolactin does not affect the induction of sexual behaviour by oestradiol and progesterone in ovariectomized rats

1983 ◽  
Vol 99 (2) ◽  
pp. 181-187 ◽  
Author(s):  
P. Södersten ◽  
S. Hansen ◽  
P. Eneroth
Keyword(s):  
Receptor Antagonist ◽  
Dopamine Receptor ◽  
Sexual Behaviour ◽  
Inhibitory Effect ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Behavioural Effect ◽  
Dopamine Receptor Antagonist ◽  
Oestradiol Benzoate ◽  
Acute Increase

Injection of 2·5 mg of the dopamine receptor antagonist domperidone raised serum prolactin concentrations within 3 h and high prolactin levels were maintained for 12 h in ovariectomized rats pretreated with 2 μg oestradiol benzoate (OB). This dose of domperidone stimulated the display of sexual behaviour in ovariectomized OB-treated rats within 3 h of administration. The behavioural effect of domperidone, but not its effect on serum prolactin concentrations, was blocked by adrenalectomy. Daily treatment with domperidone had no inhibitory effect on the subsequent induction of sexual behaviour by OB and progesterone in ovariectomized rats. A slight facilitation of the behaviour was noticed in OB-treated rats given daily domperidone injections, but this effect was cancelled by adrenalectomy. The results suggest that an acute increase in serum prolactin levels has no effect on the induction of sexual behaviour by OB in itself, but can stimulate the secretion of an adrenal product, perhaps progesterone, which facilitates the behaviour. Similarly, constant high levels of prolactin by themselves have no effect on the subsequent induction of sexual behaviour by OB and progesterone.

Role of serotoninergic neurones in the control of gonadotrophin and prolactin secretion in the rat

1982 ◽  
Vol 94 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Csilla Ruzsas ◽  
Patrizia Limonta ◽  
L. Martini
Keyword(s):  
Combined Treatment ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Intact Male ◽  
Prolactin Release ◽  
Lh Secretion ◽  
The Brain

The role of brain serotonin (5-hydroxytryptamine, 5-HT) in the control of LH, FSH and prolactin secretion was studied in two groups of experimental animals: intact adult male rats and ovariectomized adult female rats. 5-Hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, and fluoxetine, a specific inhibitor of 5-HT uptake, were given either alone or together. 5-Hydroxytryptophan (50 mg/kg) was administered intraperitoneally and fluoxetine (20 μg/rat) was given into one of the lateral ventricles of the brain. Neither 5-HTP nor fluoxetine given alone affected LH secretion but combined treatment with the two drugs elicited a significant increase in serum LH levels in both intact male and ovariectomized female rats. Fluoxetine and 5-HTP, alone or together, did not modify FSH secretion in either kind of animal. In intact males and in ovariectomized females, 5-HTP induced a significant increase in prolactin release; fluoxetine alone was ineffective. In male animals treated with fluoxetine plus 5-HTP, serum prolactin levels increased but such an increase was lower than that found in the animals treated only with 5-HTP. In ovariectomized rats, the combined treatment induced an increase in serum prolactin levels similar to that found in animals treated with 5-HTP alone. These data suggested that brain serotonin exerts a stimulating effect on LH secretion in both intact male and ovariectomized rats, but that it does not play any role in the control of FSH release in either kind of animal and that central serotoninergic pathways participate in the stimulating control of prolactin release from the anterior pituitary gland. However, some of the data also suggested the possibility of the existence in the brain of serotoninergic systems inhibiting prolactin secretion.

POSSIBLE ROLE OF 5α-ANDROSTANE-3α,17β-DIOL IN THE CONTROL OF FOLLICLE-STIMULATING HORMONE SECRETION IN THE IMMATURE FEMALE RAT

1982 ◽  
Vol 92 (1) ◽  
pp. 37-42 ◽  
Author(s):  
H. M. A. MEIJS-ROELOFS ◽  
P. KRAMER ◽  
L. GRIBLING-HEGGE
Keyword(s):  
Inhibitory Action ◽  
Combined Treatment ◽  
Hormone Secretion ◽  
Inhibitory Effect ◽  
Ovariectomized Rats ◽  
Female Rat ◽  
Immature Rat ◽  
Rat Strain ◽  
Intact Rats

A possible role of 5α-androstane-3α,17β-diol (3α-androstanediol) in the control of FSH secretion was studied at various ages in ovariectomized rats. In the rat strain used, vaginal opening, coincident with first ovulation, generally occurs between 37 and 42 days of age. If 3α-androstanediol alone was given as an ovarian substitute, an inhibitory effect on FSH release was evident with all three doses tested (50, 100, 300 μg/100 g body wt) between 13 and 30 days of age; at 33–35 days of age only the 300 μg dose caused some inhibition of FSH release. Results were more complex if 3α-androstanediol was given in combined treatment with oestradiol and progesterone. Given with progesterone, 3α-androstanediol showed a synergistic inhibitory action on FSH release between 20 and 30 days of age. However, when 3α-androstanediol was combined with oestradiol a clear decrease in effect, as compared to the effect of oestradiol alone, was found between 20 and 30 days of age. Also the effect of combined oestradiol and progesterone treatment was greater than the effect of combined treatment with oestradiol, progesterone and 3α-androstanediol. At all ages after day 20 none of the steroid combinations tested was capable of maintaining FSH levels in ovariectomized rats similar to those in intact rats. It is concluded that 3α-androstanediol might play a role in the control of FSH secretion in the immature rat, but after day 20 the potentially inhibitory action of 3α-androstanediol on FSH secretion is limited in the presence of oestradiol.

scholarly journals Dexamethasone administration attenuates the inhibitory effect of lipopolysaccharide on IGF-I and IGF-binding protein-3 in adult rats

2005 ◽  
Vol 185 (3) ◽  
pp. 467-476 ◽  
Author(s):  
Teresa Priego ◽  
Miriam Granado ◽  
Ana Isabel Martín ◽  
Asunción López-Calderón ◽  
María Angeles Villanúa
Keyword(s):  
Gene Expression ◽  
Inhibitory Effect ◽  
Mrna Levels ◽  
Serum Concentrations ◽  
Gh Receptor ◽  
Its Gene ◽  
Igf I ◽  
Igf Binding ◽  
Igf Binding Protein ◽  
Igfbp 3

The aim of this study was to investigate whether glucocorticoid administration had a beneficial effect on serum concentrations of insulin-like growth factor I (IGF-I) and on IGF-binding protein 3 (IGFBP-3) in rats injected with lipopolysaccharide (LPS). Adult male rats were injected with LPS or saline and pretreated with dexamethasone or saline. Dexamethasone administration decreased growth hormone (GH) receptor and IGF-I mRNA levels in the liver of control rats. LPS decreased GH receptor and IGF-I gene expression in the liver of saline-treated rats but not in the liver of dexamethasone-pretreated rats. In the kidney, GH receptor mRNA levels were not modified by dexamethasone or LPS treatment. However, LPS decreased renal IGF-I gene expression and dexamethasone pretreatment prevented this decrease. Serum concentrations of IGF-I were decreased by LPS, and dexamethasone pretreatment attenuated this effect. The gene expression of IGFBP-3 in the liver and kidney and its circulating levels were decreased by LPS. In control rats dexamethasone increased circulating IGFBP-3 and its gene expression in the liver, and decreased the proteolysis of this protein. Dexamethasone pretreatment attenuated the LPS-induced decrease in IGFBP-3 gene expression in the liver and prevented the LPS-induced decrease in IGFBP-3 gene expression in the kidney. Moreover, dexamethasone pretreatment attenuated the LPS-induced decrease in serum concentrations of IGFBP-3 and decreased the LPS-induced IGFBP-3 proteolysis in serum. In conclusion, dexamethasone pretreatment partially attenuates the inhibitory effect of LPS on serum IGF-I by blocking the decrease of its gene expression in the kidney as well as by attenuating the decrease in serum concentrations of IGFBP-3.

INFLUENCE OF PHOTOPERIOD ON THYROTROPIN RELEASING HORMONE-INDUCED PROLACTIN RELEASE IN EWES

1983 ◽  
Vol 63 (1) ◽  
pp. 67-73 ◽  
Author(s):  
B. E. HOWLAND ◽  
D. SONYA ◽  
L. M. SANFORD ◽  
W. M. PALMER
Keyword(s):  
Thyrotropin Releasing Hormone ◽  
Day Length ◽  
Constant Light ◽  
Serum Prolactin ◽  
Prolactin Release ◽  
Blood Samples ◽  
Releasing Hormone ◽  
Before And After ◽  
Release Curve ◽  
Short Days

The influence of photoperiod on serum prolactin levels and prolactin release induced by thyrotropin releasing hormone (TRH) was determined in ewes maintained under the following lighting regimes: Room 1, lighting mimicked natural changes in photoperiod; Room 2, annual photoperiod changes condensed into 6 mo with short days in June; Room 3, same as Room 2 except photoperiod changed abruptly from 16.5 to 8.0 h on 21 Mar. and back to 16.5 h on 21 June; Room 4, constant light. Weekly blood samples were obtained from February to August. Additionally, blood samples were collected before and after treatment with 10 μg TRH on 19 May, 13 June, 27 June and 19 July. Prolactin levels were elevated in ewes exposed to long days or constant light. The mean of all pre-TRH samples was significantly correlated with stress-induced elevations in prolactin (highest pre-TRH value) (r = 0.72) and area under the TRH-induced release curve (r = 0.56). The prolactin release in response to TRH was greatest in ewes exposed to long days or constant light. Abrupt increase of day length elevated pretreatment prolactin levels (P < 0.01) and increased area under the response curve (P < 0.05). Key words: Photoperiod, TRH, prolactin, ewes

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