Journal article
Differential Regulation of the Nocturnal and Diurnal Prolactin Surges in Pregnant Rats Revealed by Dopamine Receptor Antagonism
Neuroendocrinology, v 56(5), pp 704-711
01 Nov 1992
PMID: 1488102
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Abstract
We have explored temporal changes in the magnitude of dopamine (DA) interaction (DA tone) at the anterior pituitary lactotrophs related to both the nocturnal and diurnal prolactin (PRL) surges on day 8 of pregnancy, by utilizing a competitive DA D 2 antagonist, domperidone (DOM). After withdrawal of blood from pregnant rats on day 7 in order to demonstrate the presence of a PRL surge, experimental rats received DOM (100 µg/kg i.v. or i.a.) at various times on day 8. Blood samples were taken immediately before and following injection of DOM at 5, 15, 30 and 60 min. The peak PRL response to DOM occured 15 min after injection. Comparisons were made between circulating PRL levels immediately prior to and at several times following DOM administration for the various times of the day, and represented as incremental increases in PRL following DOM. During times on day 8 when PRL levels were normally low (24:00, 06:00, 12:00 and 16:00 h), pregnant rats exhibited a substantial PRL response to DOM. However, during the nocturnal PRL surge (02:00, 04:00 h) the peak PRL response to DOM was significantly lower. In sharp contrast, the PRL response to DOM administered during the diurnal PRL surge (18:00 h) was significantly higher than all other times of the day tested. In a dose-response study in which 10, 100 and 1,000 µg/kg DOM was administered at the two critical times when the response to DOM differed greatly, 02:00 and 18:00 h, there was a significantly reduced PRL response to DOM at 02:00 h compared to 18:00 h. This suggests that during the nocturnal PRL surge there is a decrease in DA interaction with D 2 receptors on pituitary lactotrophs compared to the diurnal PRL surge in pregnant rats. An alternative explanation is that more PRL-releasing factor is present at 18:00 h, and removal of all the DA inhibitory input to the lactotrophs allows its full expression. In either case, this study provides clear evidence that the two PRL surges during early pregnancy are under different control mechanisms.
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Details
- Title
- Differential Regulation of the Nocturnal and Diurnal Prolactin Surges in Pregnant Rats Revealed by Dopamine Receptor Antagonism
- Creators
- Joanne R. Mathiasen - University Hospital and ClinicsJames L. Voogt
- Publication Details
- Neuroendocrinology, v 56(5), pp 704-711
- Number of pages
- 8
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Pharmacology and Physiology
- Web of Science ID
- WOS:A1992KF09800015
- Scopus ID
- 2-s2.0-0027065522
- Other Identifier
- 991021900194504721
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InCites Highlights
Data related to this publication, from InCites Benchmarking & Analytics tool:
- Web of Science research areas
- Endocrinology & Metabolism
- Neurosciences