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.

scholarly journals The regulation by ovarian steroids of prostaglandin synthesis and prostaglandin-induced contractility in non-pregnant rat myometrium. Modulating effects of isoproterenol

2001 ◽  
Vol 169 (1) ◽  
pp. 33-41 ◽  
Author(s):  
T Engstrom
Keyword(s):  
Prostaglandin Synthesis ◽  
Ovariectomized Rats ◽  
Oestrogen Treatment ◽  
Pregnant Rat ◽  
Progesterone Treatment ◽  
Myometrial Contractility ◽  
Cox 2 ◽  
Beta 2 ◽  
Relaxing Effect ◽  
Isoproterenol Infusion

The objectives of the present study were to investigate the effects of the reproductive steroids oestradiol and progesterone on myometrial levels of cyclooxygenase-2 (COX-2) mRNA and PGF(2alpha) induced myometrial contractility and to study whether the effect of beta(2)-adrenoceptor stimulation by isoproterenol on the myometrium alters these parameters. Oestrogen treatment of ovariectomized rats increased myometrial COX-2 mRNA whereas PGF(2alpha) receptor (PGF(2alpha)-R) mRNA was unchanged following this treatment and maximal contractility (E(max)) of isolated uterine strips challenged with PGF(2alpha) was unaltered. Progesterone treatment alone decreased COX-2 mRNA in comparison with values obtained from oestrogen-treated animals, and in combination with oestrogen the enhancing effect of progesterone on COX-2 mRNA was curbed. EC(50) of uterine strips challenged with PGF(2alpha) increased following oestrogen treatment whereas this parameter was substantially decreased following progesterone treatment. When oestrogen was combined with isoproterenol infusion mRNA values of both COX-2 and PGF(2alpha)-R were reduced. Finally, when isoproterenol infusions were given in combination with both oestrogen and progesterone, PGF(2alpha)-R mRNA and E(max )were enhanced as compared with similar rats not having received isoproterenol. We conclude that oestrogen increases COX-2 mRNA production and subsequent prostaglandin synthesis in non-pregnant rat myometrium. We further conclude that in the oestrogen-dominated rat myometrium the relaxing effect of beta(2)-adrenoceptor stimulation involves attenuation of both prostaglandin synthesis and PGF(2alpha)-R expression. We finally conclude that in the presence of both oestrogen and progesterone this effect of beta(2)-adrenoceptor stimulation is restrained.

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.

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.

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

Effect of oestrogen treatment on gonadotroph function in adult male rats

1987 ◽  
Vol 114 (1) ◽  
pp. 95-101 ◽  
Author(s):  
G. Saade ◽  
D. R. London ◽  
R. N. Clayton
Keyword(s):  
Adult Male ◽  
Term Treatment ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Control Group ◽  
Oestrogen Treatment ◽  
Serum Lh ◽  
Long Term Treatment

ABSTRACT The effect of oestradiol-17β on the hypothalamo-pituitary axis of intact adult male rats was studied. A single injection of oestradiol did not change the serum LH response to gonadotrophin-releasing hormone (GnRH) 48 h or 7 days after the injection, while administration of oestrogen over 66 days suppressed basal serum LH to <3·1 μg/l and did not enhance the LH response to GnRH at any time. Treatment of ovariectomized rats with oestradiol capsules, however, enhanced the LH response to GnRH on days 3 and 14 of the treatment as compared with the control group (P<0·02 and P<0·05 respectively). Long-term treatment with oestradiol suppressed intrapituitary LH and FSH contents as well as pituitary GnRH receptors (P<0·0004, P<0·005 and P<0·001 respectively), whereas serum and intrapituitary prolactin levels were increased. To exclude the possible inhibitory effect of hyperprolactinaemia on LH responsiveness to GnRH, oestradiol-implanted rats were treated with bromocriptine. This prevented the rise in serum prolactin, but failed to enhance the LH response to GnRH. Neither short- nor long-term treatment with oestradiol given under conditions shown to be effective in female animals stimulated the hypothalamo-pituitary-gonadotrophin axis in adult male rats. J. Endocr. (1987) 114,95–101

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.

Changes in the characteristics of pulsatile luteinizing hormone secretion during the oestrous cycle and after ovariectomy and oestrogen treatment in female rats

1982 ◽  
Vol 94 (2) ◽  
pp. 177-182 ◽  
Author(s):  
Takashi Higuchi ◽  
Masazumi Kawakami
Keyword(s):  
Hormone Secretion ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Luteinizing Hormone Secretion ◽  
Oestrogen Treatment ◽  
Serum Lh ◽  
Lh Release

Changes in the characteristics of LH secretory pulses in female rats were determined in different hormonal conditions; during the oestrous cycle and after ovariectomy and oestrogen treatment. The frequency and amplitude of the LH pulses were stable during the oestrous cycle except at oestrus when a pattern could not be discerned because of low LH concentrations. These were significantly lower than those measured during other stages of the cycle. Mean LH concentrations and LH pulse amplitudes increased with time up to 30 days after ovariectomy. The frequency of the LH pulse was unchanged 4 days after ovariectomy when mean LH levels had already increased. The frequency increased 10 days after ovariectomy and then remained stable in spite of a further increase in mean serum LH concentrations. Oestradiol-17β injected into ovariectomized rats caused a decrease in LH pulse amplitude but no change in pulse frequency. One day after treatment with oestradiol benzoate no LH pulse was detectable, probably because the amplitude was too small. A generator of pulsatile LH release is postulated and an oestrogen effect on its function is discussed.

HORMONAL REQUIREMENTS FOR THE MAINTENANCE OF OESTRADIOL-INDUCED INHIBITION OF UTERINE SENSITIVITY IN THE OVARIECTOMIZED RAT

1970 ◽  
Vol 46 (3) ◽  
pp. 341-346 ◽  
Author(s):  
K. P. MEYERS
Keyword(s):  
Subcutaneous Injection ◽  
Ovariectomized Rats ◽  
Ovariectomized Rat ◽  
Single Subcutaneous Injection ◽  
The Third ◽  
Oestradiol Treatment ◽  
Progesterone Treatment ◽  
Endometrial Scratching

SUMMARY Ovariectomized rats treated with 2·5 or 5·0 mg. progesterone daily received a single subcutaneous injection of 0·2 μg. oestradiol on the third day of the progesterone treatment. The deciduomal response to trauma by endometrial scratching was used to determine the degree of uterine sensitivity at various times after oestradiol. Uterine sensitivity was partially and then completely lost 36 and 48 hr. after oestradiol administration. The inhibition of uterine sensitivity persisted until 9 and 11 days after oestradiol when the animals received 2·5 and 5·0 mg. progesterone daily. Uterine sensitivity was completely inhibited on day 11 with doses of oestradiol from 0·2 to 0·05 μg. Withdrawal of progesterone treatment for 48 or 72 hr., but not for 24 hr., after oestradiol treatment restored uterine sensitivity. These results show that the oestradiol-induced inhibition of uterine sensitivity in the progestational endometrium is maintained by continuous progesterone treatment and that the duration of this effect is dependent on the dose of progesterone given.

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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