Role of Oxytocin in Prolactin Secretion during Late Pregnancy

2017 ◽  
Vol 106 (4) ◽  
pp. 324-334 ◽  
Author(s):  
Carlos M. Villegas-Gabutti ◽  
Gisela E. Pennacchio ◽  
Laura Vivas ◽  
Graciela A. Jahn ◽  
Marta Soaje
Keyword(s):  
Elevated Serum ◽  
Late Pregnancy ◽  
Prolactin Secretion ◽  
Rt Pcr ◽  
Stimulatory Action ◽  
Paraventricular Nuclei ◽  
Dopaminergic Tone ◽  
Pituitary Prolactin ◽  
Supraoptic Nuclei

Background/Aims: During late pregnancy, the blockade of progesterone action by mifepristone (Mp) treatment induces a dopaminergic tone fall that enables naloxone (NAL) administration to release pituitary prolactin (PRL). We determined whether oxytocin (OT), which stimulates PRL secretion acting directly on anterior pituitary lactotrophs, mediates the stimulatory action of Mp and NAL on PRL secretion during late pregnancy. Methods: On day 19 of pregnancy, circulating and pituitary OT and PRL levels were measured by radioimmunoassay, 10, 20, and 30 min after NAL (given at 17:30 h) in rats pretreated with Mp (at 08:00 h). Pituitary OT receptor (OTR) expression in Mp-treated rats was evaluated by RT-PCR. Activation of OT neurons in Mp-NAL-treated rats was measured counting double immunoreactive neurons for Fos and OT (Fos-OT-ir) in supraoptic nuclei (SON), and medial (PaMM) and lateral magnocellular divisions of paraventricular nuclei. Results: Elevated serum OT and decreased pituitary OT were observed 10 min after NAL administration in both vehicle- and Mp-treated rats. This PRL increase was prevented by previous i.p. administration of an OTR antagonist, but intracerebroventricular OT administration was ineffective. Mp increased pituitary OTR expression at 18:00 h. Only Mp-NAL increased Fos-OT-ir neurons in the PaMM and SON. Conclusions: These findings suggest that PRL secretion induced by Mp-NAL treatment is preceded by OT release. These results, together with the activation of hypothalamic OT neurons and the higher expression of pituitary OTR, support the hypothesis that, during late pregnancy, OT may act at the pituitary level to facilitate PRL secretion if the inhibitory action of progesterone is blocked.

Effect of progesterone on the activation of neurones of the supraoptic nucleus during parturition

Reproduction ◽  
2000 ◽  
pp. 367-376 ◽  
Author(s):  
IA Antonijevic ◽  
JA Russell ◽  
RJ Bicknell ◽  
G Leng ◽  
AJ Douglas
Keyword(s):  
Progesterone Receptor ◽  
Supraoptic Nucleus ◽  
Late Pregnancy ◽  
Endogenous Opioids ◽  
Opioid Antagonist ◽  
Endogenous Opioid ◽  
Fos Expression ◽  
Oxytocin Neurones ◽  
Supraoptic Nuclei

Parturition is driven by a pulsatile pattern of oxytocin secretion, resulting from burst firing activity of supraoptic oxytocin neurones and reflected by induction of Fos expression. Rats were injected with progesterone on day 20 of pregnancy to investigate the role of the decreasing progesterone:ratio oestrogen ratio, which precedes delivery, in the activation of supraoptic neurones. Progesterone delayed the onset of birth by 28 h compared with vehicle (control) and prolonged the duration of delivery, which was overcome by pulsatile injections of oxytocin, indicating that the slow delivery may reflect impaired oxytocin secretion. Parturient rats pretreated with progesterone had fewer Fos immunoreactive nuclei in the supraoptic nucleus than did parturient rats pretreated with vehicle. The number of Fos immunoreactive nuclei was not restored after oxytocin injection, indicating that appropriate activation of oxytocin neurones is impaired by progesterone and also that there is a lack of stimulatory afferent drive. Fos expression increased in the nucleus of the tractus solitarius during parturition in rats pretreated with either vehicle or progesterone, but not in rats that had been pretreated with progesterone and induced with oxytocin, indicating that this input was inhibited. Endogenous opioids inhibit oxytocin neurones in late pregnancy and the opioid antagonist, naloxone, increases Fos expression in supraoptic nuclei by preventing inhibition. However, progesterone attenuated naloxone-induced Fos expression in the supraoptic nucleus in late pregnancy and naloxone administered during parturition did not accelerate the duration of births delayed by progesterone administration, indicating that progesterone does not act by hyperactivation of endogenous opioid tone. RU486, a progesterone receptor antagonist, enhanced supraoptic neurone Fos expression in late pregnancy, indicating progesterone receptor-mediated actions. Thus, progesterone withdrawal is necessary for appropriate activation of supraoptic and tractus solitarius neurones during parturition.

Opioid modulation of prolactin secretion induced by stress during late pregnancy. Role of ovarian steroids

2014 ◽  
Vol 66 (3) ◽  
pp. 386-393 ◽  
Author(s):  
Susana R. Valdez ◽  
Gisela E. Pennacchio ◽  
Dante F. Gamboa ◽  
Elina G. de Di Nasso ◽  
Claudia Bregonzio ◽  
...  
Keyword(s):  
Late Pregnancy ◽  
Prolactin Secretion ◽  
Ovarian Steroids

Role of Estradiol in the Regulation of Prolactin Secretion During Late Pregnancy

2016 ◽  
Vol 41 (12) ◽  
pp. 3344-3355 ◽  
Author(s):  
Carlos Villegas-Gabutti ◽  
Gisela E. Pennacchio ◽  
Graciela A. Jahn ◽  
Marta Soaje
Keyword(s):  
Late Pregnancy ◽  
Prolactin Secretion

Role of the placenta in the control of the ante-partum surge of prolactin in the rat

1991 ◽  
Vol 130 (3) ◽  
pp. 401-407 ◽  
Author(s):  
D. R. Grattan ◽  
R. L. W. Averill
Keyword(s):  
Early Pregnancy ◽  
Feedback Inhibition ◽  
Dark Period ◽  
Late Pregnancy ◽  
Complete Removal ◽  
Prolactin Secretion ◽  
Placental Lactogen ◽  
Surgical Removal ◽  
Plasma Prolactin

ABSTRACT A nocturnal surge of prolactin secretion occurs in the dark period preceding parturition in the rat. The aim of this study was to examine the role of the placenta in the control of this prolactin surge. Plasma prolactin and progesterone were measured by radioimmunoassay in serial blood samples collected after surgical removal of conceptuses during late pregnancy, and after intracerebroventricular (i.c.v.) injection of placental lactogen (PL) before the prolactin surge. In intact control animals, prolactin secretion remained low until a nocturnal surge of secretion occurred in the dark period preceding parturition, peaking at 269±51 (s.e.m.) μg/l at 03.00 h on day 21. Progesterone levels fell from > 200 nmol/l on day 19 to <40 nmol/l by 12.00 h on day 20 of pregnancy. PL levels during late pregnancy were modified by partial or complete removal of conceptuses at 10.00 h on day 19 of pregnancy. Removal of all but one or two conceptuses did not change the normal pattern of prolactin or progesterone secretion. Removal of all conceptuses, however, induced a large nocturnal surge of prolactin secretion, peaking at 211·7±78 μg/l at 03.00 h on day 20, 24 h earlier than the surge in intact animals. Progesterone levels after removal of all conceptuses fell to <40 nmol/l by 23.00 h on day 19, approximately 12 h before the decline in intact animals. Maintenance of increased progesterone levels after conceptus removal using silicone tubing implants significantly (P <0·05) reduced the peak of the premature prolactin surge to 79·7 ±18 μg/l at 05.00 h on day 20. To determine whether PL could act at the hypothalamic level to inhibit the prolactin surge, human PL was injected into the lateral ventricle. PL injected i.c.v. at 17.00 h on day 7 of pregnancy completely abolished both the expected diurnal and nocturnal prolactin surges in the subsequent 24 h. By contrast, the same treatment on day 20 of pregnancy had no effect on the ante-partum prolactin surge. These results demonstrate two changes in the mechanisms controlling prolactin secretion on the last day of pregnancy compared with prolactin secretion during early pregnancy. First, feedback inhibition of prolactin secretion by PL which occurs at mid-pregnancy was not functional on the last day of pregnancy. Secondly, progesterone which promotes the nocturnal prolactin surges of early pregnancy, inhibited prolactin secretion during late pregnancy. Journal of Endocrinology (1991) 130, 401–407

scholarly journals Regulation by endogenous opioids of suckling-induced prolactin secretion in pregnant and lactating rats: role of ovarian steroids

2002 ◽  
Vol 172 (2) ◽  
pp. 255-261 ◽  
Author(s):  
M Soaje ◽  
EG de Di Nasso ◽  
RP Deis
Keyword(s):  
Inhibitory Effect ◽  
Prolactin Secretion ◽  
Endogenous Opioids ◽  
Opioid System ◽  
Serum Prolactin ◽  
Endogenous Opioid Peptides ◽  
Endogenous Opioid ◽  
Subsequent Increase ◽  
Stimulatory Action

Evidence suggests that endogenous opioid peptides are implicated in the suckling-induced prolactin rise. We explored the role of the opioid system and the participation of ovarian hormones in the regulation of prolactin induced by the suckling stimulus at the end of pregnancy in rats with developed maternal behavior, and during lactation. Suckling for 24 h induced a significant increase in serum prolactin on day 19 of pregnancy, which was increased more than three times when naloxone (2 mg/kg s.c.) or mifepristone (2 mg/kg) was administered. The combination of naloxone and mifepristone did not increase serum prolactin more than either compound alone. Administration of tamoxifen (500 microg/kg orally) on days 14 and 15 of pregnancy completely abolished the effect of naloxone, indicating a role for estrogens in establishing this inhibitory role of opioids. To examine the participation of the opioid system during lactation, we used groups of rats on days 1, 3, 5, 12 and 19 postpartum either (i) isolated from the pups for 4 h, or (ii) isolated from the pups for 3.5 h and reunited with them and suckled for 30 min. Naloxone, given just before replacing the pups, prevented the increase in serum prolactin levels observed in the suckled group of rats but had no effect on the basal levels of the isolated rats. To examine whether the participation of the opioid system in the release of prolactin is dependent on the variation of progesterone levels, rats on day 20 of pregnancy were implanted with two cannulae containing progesterone (that blocked postpartum ovulation) or cholesterol, and cesarean surgery was performed on day 21. To maintain lactation, pups (1-3 days old) were replaced every 24 h, and 4 days after the cesarean eight pups were placed in the cage at 1800 h to maintain a strong suckling stimulus during the following 24 h. Naloxone administration significantly reduced serum prolactin levels in control (cholesterol) rats but progesterone implants prevented the inhibitory effect of naloxone and this effect was not modified by treatment with estrogen. These results indicate that the opioid system modulates suckling-induced prolactin secretion, passing from an inhibitory action before delivery to a stimulatory action during lactation. This regulatory shift seems to be dependent on the fall in progesterone concentration at the end of pregnancy and the subsequent increase after the postpartum ovulation and luteal phase.

ROLE OF THE MEDICAL–BASAL HYPOTHALAMUS IN THE SECRETION OF GROWTH HORMONE DURING PREGNANCY AND LACTATION IN EWES

1981 ◽  
Vol 89 (3) ◽  
pp. 349-354 ◽  
Author(s):  
BARBARA WRÓBLEWSKA ◽  
E. DOMAŃSKI
Keyword(s):  
Growth Hormone ◽  
Peripheral Blood ◽  
Marked Decrease ◽  
Late Pregnancy ◽  
Peripheral Circulation ◽  
Prolactin Secretion ◽  
Medial Basal Hypothalamus ◽  
Pregnancy And Lactation

The main aim of this study was to examine the role of the hypothalamus in controlling the secretion of GH in the ewe. This was evaluated by studying the effect of lesions placed either in the anterior or the posterior medial–basal hypothalamus (MBH) on the concentration of GH in the peripheral circulation during pregnancy and lactation, i.e. when the levels would be high in normal ewes. Simultaneously, the level of prolactin in the peripheral blood of these animals was followed. Lesions of the MBH resulted in a marked decrease in circulating GH as well as disturbances in the mammogenic and lactogenic processes during the periods of periparturition and lactation respectively. The changes were particularly evident if the anterior MBH was lesioned. The present experiments confirm our previous findings that a stimulatory centre is localized in the anterior MBH of sheep whilst in the caudal MBH there is an inhibitory centre regulating the release of prolactin. The results also confirm the important role of GH during lactation in ewes, especially during lactogenesis. The results indicate a differentiated but synchronizing and synergistic role of the MBH regulating the patterns of GH and prolactin secretion in late pregnancy and lactation.

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

1984 ◽  
Vol 143 (3) ◽  
pp. 305-313 ◽  
Author(s):  
KEIICHI MINATO ◽  
KATSUYUKI TAKAHASHI ◽  
NOBUKO IKENO ◽  
MASAAKI WATANABE ◽  
HIROSHI ENDO ◽  
...  
Keyword(s):  
Pineal Gland ◽  
Prolactin Secretion ◽  
Female Rats ◽  
Pituitary Prolactin

PLASMA CORTICOSTERONE CONCENTRATIONS AND PITUITARY PROLACTIN CONTENT IN LATE PREGNANCY AND THEIR WITHIN-DAY FLUCTUATIONS IN THE RAT

1974 ◽  
Vol 61 (1) ◽  
pp. 21-28 ◽  
Author(s):  
KATUAKI ÔTA ◽  
TAKAO ÔTA ◽  
AKIRA YOKOYAMA
Keyword(s):  
Late Pregnancy ◽  
Plasma Corticosterone ◽  
Prolactin Secretion ◽  
Corticosterone Concentration ◽  
Corticosterone Secretion ◽  
Prolactin Content ◽  
Pituitary Prolactin

SUMMARY Levels of plasma corticosterone and of pituitary prolactin were studied in the mornings (10.00–10.30 h) and evenings (17.00–18.00 h) during the last week of pregnancy in the rat. Morning levels of plasma corticosterone started to rise on day 19 and reached a peak on day 21. The concentration of corticosterone in plasma on the morning of day 21 was about 2·3 times higher than that on day 15. Both content and concentration of prolactin in the pituitary began to fall on the morning of day 19 of pregnancy and the minimum values for both content and concentration were reached on the morning of day 21. Plasma corticosterone concentration and pituitary prolactin content measured in the evening, however, remained high throughout the period examined and there were no appreciable changes in the levels at the different stages of pregnancy. The results obtained on day 22 of pregnancy, the expected day of parturition, indicated that a surge of pituitary prolactin secretion and a temporary depression of corticosterone secretion occurred at about the time of parturition.

Monitoring the marine environment for small round structured viruses (SRSVS): a new approach to combating the transmission of these viruses by molluscan shellfish

1998 ◽  
Vol 38 (12) ◽  
pp. 51-56 ◽  
Author(s):  
K. Henshilwood ◽  
J. Green ◽  
D. N. Lees
Keyword(s):  
Enteric Virus ◽  
Winter Period ◽  
Rt Pcr ◽  
Cloning And Sequencing ◽  
New Approach ◽  
Human Enteric Virus ◽  
Different Strains ◽  
The Uk ◽  
Public Health Protection

This study investigates human enteric virus contamination of a shellfish harvesting area. Samples were analysed over a 14-month period for Small Round Structured Viruses (SRSVs) using a previously developed nested RT-PCR. A clear seasonal difference was observed with the largest numbers of positive samples obtained during the winter period (October to March). This data concurs with the known winter association of gastroenteric illness due to oyster consumption in the UK and also with the majority of the outbreaks associated with shellfish harvested from this area during the study period. RT-PCR positive amplicons were further characterised by cloning and sequencing. Sequence analysis of the positive samples identified eleven SRSV strains, of both Genogroup I and Genogroup II, occurring throughout the study period. Many shellfish samples contained a mixture of strains with a few samples containing up to three different strains with both Genogroups represented. The observed common occurrence of strain mixtures may have implications for the role of shellfish as a vector for dissemination of SRSV strains. These results show that nested RT-PCR can identify SRSV contamination in shellfish harvesting areas. Virus monitoring of shellfish harvesting areas by specialist laboratories using RT-PCR is a possible approach to combating the transmission of SRSVs by molluscan shellfish and could potentially offer significantly enhanced levels of public health protection.

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