The nature of the circadian signal from the suprachiasmatic nucleus (SCN) required for prolactin (PRL) surges is unknown. Because the SCN neuronal circadian rhythm is determined by a feedback loop of Period (Per) 1, Per2, and circadian locomotor output cycles kaput (Clock) gene expressions, we investigated the effect of SCN rhythmicity on PRL surges by disrupting this loop. Because lesion of the locus coeruleus (LC) abolishes PRL surges and these neurons receive SCN projections, we investigated the role of SCN rhythmicity in the LC neuronal circadian rhythm as a possible component of the circadian mechanism regulating PRL surges. Cycling rats on proestrous day and estradiol-treated ovariectomized rats received injections of antisense or random-sequence deoxyoligonucleotide cocktails for clock genes (Per1, Per2, and Clock) in the SCN, and blood samples were taken for PRL measurements. The percentage of tyrosine hydroxylase-positive neurons immunoreactive to Fos-related antigen (FRA) was determined in ovariectomized rats submitted to the cocktail injections and in a 12:12-h light:dark (LD) or constant dark (DD) environment. The antisense cocktail abolished both the proestrous and the estradiol-induced PRL surges observed in the afternoon and the increase of FRA expression in the LC neurons at Zeitgeber time 14 in LD and at circadian time 14 in DD. Because SCN afferents and efferents were probably preserved, the SCN rhythmicity is essential for the magnitude of daily PRL surges in female rats as well as for LC neuronal circadian rhythm. SCN neurons therefore determine PRL secretory surges, possibly by modulating LC circadian neuronal activity.
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http://dx.doi.org/10.1152/ajpendo.00341.2007 | DOI Listing |
Endocr J
July 2024
Department of Integrative Physiology, Gunma University Graduate School of Medicine, Gunma 371-8511, Japan.
The placenta secretes a prolactin (PRL)-like hormone PRL3B1 (placental lactogen II), a luteotropic hormone essential for maintaining pregnancy until labor in mice. A report from 1984 examined the secretion pattern of PRL3B1 in prepartum mice. In the current study, we found contradictory findings in the secretion pattern that invalidate the previous report.
View Article and Find Full Text PDFEndocrinology
June 2023
Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
The RF-amide peptides comprise a family of neuropeptides that includes the kisspeptin (Kp), the natural ligand of kisspeptin receptor (Kiss1r), and the RFamide-related peptide 3 (RFRP-3) that binds preferentially to the neuropeptide FF receptor 1 (Npffr1). Kp stimulates prolactin (PRL) secretion through the inhibition of tuberoinfundibular dopaminergic (TIDA) neurons. Because Kp also has affinity to Npffr1, we investigated the role of Npffr1 in the control of PRL secretion by Kp and RFRP-3.
View Article and Find Full Text PDFJ Neuroendocrinol
November 2022
Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Kisspeptin, neurokinin, and dynorphin (KNDy) neurons in the arcuate nucleus (ARC) control luteinizing hormone (LH) and prolactin (PRL) release, although their role in conveying the effects of estradiol (E ) to these hormones is not well understood. We performed a longitudinal evaluation of female rats in which KNDy neurons were ablated using a neurokinin-3 receptor agonist conjugated with saporin (NK3-SAP) to investigate the impact of the reduction of KNDy neurons on the E regulation of gonadal and PRL axes. NK3-SAP rats, bearing a moderate loss of ARC kisspeptin-immunoreactive (-IR) neurons (50%-90%), displayed irregular estrous cycles but essentially unaltered follicular development and a normal number of corpora lutea.
View Article and Find Full Text PDFInt J Environ Res Public Health
October 2020
Department of Dermatology, Venerology and Pediatric Dermatology, Medical University of Lublin, ul. Radziwiłłowska 13, 20-080 Lublin, Poland.
One of the major problems of success in infertility treatment could depend on the understanding how the potential factors may affect the conception. The aim of this study was to evaluate present understanding of such factors or hormonal causes that may induce infertility. We studied the interactions between the two menstrual cycle hormones i.
View Article and Find Full Text PDFJ Endocrinol Invest
May 2021
Department of Biochemistry, Gaziantep University, Faculty of Medicine, Gaziantep, Turkey.
Purpose: Iodine plays a pivotal role in adaptation during the transition from intrauterine to extrauterine life. Although it is well known that the placenta plays a role in iodine storage, a relationship between the neonatal thyroid stimulating hormone (TSH) peak and placental iodine concentration has not been established. This study focuses on the role of placental iodine concentration in the TSH surge after delivery.
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