1
|
McGrath BM, Norman ST, Gaspardis CA, Rose JL, Scott CJ. Characterizing the relationship between gonadotropin releasing hormone (GnRH), kisspeptin, and RFamide related peptide 3 (RFRP-3) neurons in the equine hypothalamus across the estrous cycle and in the anovulatory seasons. Theriogenology 2024; 219:157-166. [PMID: 38432143 DOI: 10.1016/j.theriogenology.2024.02.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 02/26/2024] [Accepted: 02/26/2024] [Indexed: 03/05/2024]
Abstract
To understand better the role that kisspeptin plays in regulating seasonal and estrous cycle changes in the mare, this study investigated the number, location and interactions between GnRH, kisspeptin and RFRP-3 neurons in the equine hypothalamus. Hypothalami were collected from mares during the non-breeding season, vernal transition and various stages of the breeding season. Fluorescent immunohistochemistry was used to label the neuropeptides of interest. GnRH cells were observed primarily in the arcuate nucleus (ARC), while very few labeled cells were identified in the pre-optic area (POA). Kisspeptin cells were identified primarily in the ARC, with a small number of cells observed dorsal to the ARC, surrounding the third ventricle (3V). The mean number of kisspeptin cells varied between animals and typically showed no pattern associated with season or stage of estrous cycle, but a seasonal difference was identified in the ARC population. Small numbers of RFRP-3 cells were observed in the ARC, ventromedial hypothalamus (VMH) and dorsomedial hypothalamus (DMH). The mean number of RFRP-3 cells appeared higher in pre-ovulatory animals compared to all other stages. The percentage of GnRH cell bodies with kisspeptin appositions did not change with season or stage of estrous cycle. The percentage of kisspeptin cells receiving inputs from RFRP-3 fibers did not vary with season or stage of estrous cycle. These interactions suggest the possibility of the presence of an ultra-short loop feedback system between these three peptides. The changes in RFRP-3 neurons suggest the possibility of a role in the regulation of reproduction in the horse, but it is unlikely to be as a gonadotropin inhibitory factor.
Collapse
Affiliation(s)
- B M McGrath
- School of Dentistry & Medical Sciences, Locked bag 588, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia.
| | - S T Norman
- School of Animal and Veterinary Sciences, Locked bag 588, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia.
| | - C A Gaspardis
- School of Animal and Veterinary Sciences, Locked bag 588, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia.
| | - J L Rose
- School of Dentistry & Medical Sciences, Locked bag 588, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia.
| | - C J Scott
- School of Dentistry & Medical Sciences, Locked bag 588, Charles Sturt University, Wagga Wagga, NSW, 2678, Australia.
| |
Collapse
|
2
|
Does kisspeptin participate in GABA-mediated modulation of GnRH and GnRH receptor biosynthesis in the hypothalamic-pituitary unit of follicular-phase ewes? Pharmacol Rep 2019; 71:636-643. [PMID: 31176893 DOI: 10.1016/j.pharep.2019.02.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/25/2019] [Accepted: 02/28/2019] [Indexed: 11/24/2022]
Abstract
BACKGROUND The inverse relationship between GnRH transcript level and GABA neurons activity has suggested that GABA at the hypothalamic level may exert a suppressive effect on subsequent steps of the GnRH biosynthesis. In the present study, we analyzed the effects of GABA type A receptor agonist (muscimol) or antagonist (bicuculline) on molecular mechanisms governing GnRH/LH secretion in follicular-phase sheep. METHODS ELISA technique was used to investigate the effects of muscimol and/or bicuculline on levels of post-translational products of genes encoding GnRH ligand and GnRH receptor (GnRHR) in the preoptic area (POA), anterior (AH) and ventromedial (VMH) hypothalamus, stalk/median eminence (SME), and GnRHR in the anterior pituitary (AP). Real-time PCR was chosen for determination of the effect of drugs on kisspeptin (Kiss 1) mRNA level in POA and VMH including arcuate nucleus (VMH/ARC), and on Kiss1 receptor (Kiss1r) mRNA abundance in POA-hypothalamic structures. These analyses were supplemented by RIA method for measurement of plasma LH concentration. RESULTS The study demonstrated that muscimol and bicuculline significantly decreased or increased GnRH biosynthesis in all analyzed structures, respectively, and led to analogous changes in plasma LH concentration. Similar muscimol- and bicuculline-related alterations were observed in levels of GnRHR. However, the expression of Kiss 1 and Kiss1r mRNAs in selected POA-hypothalamic areas of either muscimol- and bicuculline-treated animals remained unaltered. CONCLUSIONS Our data suggest that GABAergic neurotransmission is involved in the regulatory pathways of GnRH/GnRHR biosynthesis and then GnRH/LH release in follicular-phase sheep conceivably via indirect mechanisms that exclude involvement of Kiss 1 neurons.
Collapse
|
3
|
DeAtley KL, Colgrave ML, Cánovas A, Wijffels G, Ashley RL, Silver GA, Rincon G, Medrano JF, Islas-Trejo A, Fortes MRS, Reverter A, Porto-Neto L, Lehnert SA, Thomas MG. Neuropeptidome of the Hypothalamus and Pituitary Gland of Indicine × Taurine Heifers: Evidence of Differential Neuropeptide Processing in the Pituitary Gland before and after Puberty. J Proteome Res 2018; 17:1852-1865. [PMID: 29510626 DOI: 10.1021/acs.jproteome.7b00875] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Puberty in cattle is regulated by an endocrine axis, which includes a complex milieu of neuropeptides in the hypothalamus and pituitary gland. The neuropeptidome of hypothalamic-pituitary gland tissue of pre- (PRE) and postpubertal (POST) Bos indicus-influenced heifers was characterized, followed by quantitative analysis of 51 fertility-related neuropeptides in these tissues. Comparison of peptide abundances with gene expression levels allowed assessment of post-transcriptional peptide processing. On the basis of classical cleavage, 124 mature neuropeptides from 35 precursor proteins were detected in hypothalamus and pituitary gland tissues of three PRE and three POST Brangus heifers. An additional 19 peptides (cerebellins, PEN peptides) previously reported as neuropeptides that did not follow classical cleavage were also identified. In the pre-pubertal hypothalamus, a greater diversity of neuropeptides (25.8%) was identified relative to post-pubertal heifers, while in the pituitary gland, 38.6% more neuropeptides were detected in the post-pubertal heifers. Neuro-tissues of PRE and POST heifers revealed abundance differences ( p < 0.05) in peptides from protein precursors involved in packaging and processing (e.g., the granin family and ProSAAS) or neuron stimulation (PENK, CART, POMC, cerebellins). On their own, the transcriptome data of the precursor genes could not predict the neuropeptide profile in the exact same tissues in several cases. This provides further evidence of the importance of differential processing of the neuropeptide precursors in the pituitary before and after puberty.
Collapse
Affiliation(s)
- Kasey L DeAtley
- Department of Animal and Range Sciences , New Mexico State University , Las Cruces , New Mexico 88003 , United States
| | - Michelle L Colgrave
- CSIRO, Agriculture and Food , 306 Carmody Road , St. Lucia , Queensland 4067 , Australia
| | - Angela Cánovas
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences , University of Guelph , Guelph , Ontario N1G 2W1 , Canada
| | - Gene Wijffels
- CSIRO, Agriculture and Food , 306 Carmody Road , St. Lucia , Queensland 4067 , Australia
| | - Ryan L Ashley
- Department of Animal and Range Sciences , New Mexico State University , Las Cruces , New Mexico 88003 , United States
| | - Gail A Silver
- Department of Animal and Range Sciences , New Mexico State University , Las Cruces , New Mexico 88003 , United States
| | - Gonzalo Rincon
- Zoetis Animal Health , Kalamazoo , Michigan 49007 , United States
| | - Juan F Medrano
- Department of Animal Science , University of California , Davis , California 95616 , United States
| | - Alma Islas-Trejo
- Department of Animal Science , University of California , Davis , California 95616 , United States
| | - Marina R S Fortes
- School of Chemistry and Molecular Biosciences , University of Queensland , St. Lucia , Queensland 4042 , Australia
- Queensland Alliance for Agriculture and Food Innovation, St. Lucia , Queensland 4072 , Australia
| | - Antonio Reverter
- CSIRO, Agriculture and Food , 306 Carmody Road , St. Lucia , Queensland 4067 , Australia
| | - Laercio Porto-Neto
- CSIRO, Agriculture and Food , 306 Carmody Road , St. Lucia , Queensland 4067 , Australia
| | - Sigrid A Lehnert
- CSIRO, Agriculture and Food , 306 Carmody Road , St. Lucia , Queensland 4067 , Australia
| | - Milton G Thomas
- Department of Animal Sciences , Colorado State University , Fort Collins , Colorado 80523 , United States
| |
Collapse
|
4
|
Melo L, Monteiro P, Nascimento A, Drum J, Spies C, Prata A, Wiltbank M, Sartori R. Follicular dynamics, circulating progesterone, and fertility in Holstein cows synchronized with reused intravaginal progesterone implants that were sanitized by autoclave or chemical disinfection. J Dairy Sci 2018; 101:3554-3567. [DOI: 10.3168/jds.2017-13570] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 12/05/2017] [Indexed: 11/19/2022]
|
5
|
Ciechanowska M, Łapot M, Paruszewska E, Radawiec W, Przekop F. The influence of dopaminergic system inhibition on biosynthesis of gonadotrophin-releasing hormone (GnRH) and GnRH receptor in anoestrous sheep; hierarchical role of kisspeptin and RFamide-related peptide-3 (RFRP-3). Reprod Fertil Dev 2018; 30:672-680. [DOI: 10.1071/rd16309] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 09/14/2017] [Indexed: 11/23/2022] Open
Abstract
This study aimed to explain how prolonged inhibition of central dopaminergic activity affects the cellular processes governing gonadotrophin-releasing hormone (GnRH) and LH secretion in anoestrous sheep. For this purpose, the study included two experimental approaches: first, we investigated the effect of infusion of sulpiride, a dopaminergic D2 receptor antagonist (D2R), on GnRH and GnRH receptor (GnRHR) biosynthesis in the hypothalamus and on GnRHR in the anterior pituitary using an immunoassay. This analysis was supplemented by analysis of plasma LH levels by radioimmunoassay. Second, we used real-time polymerase chain reaction to analyse the influence of sulpiride on the levels of kisspeptin (Kiss1) mRNA in the preoptic area and ventromedial hypothalamus including arcuate nucleus (VMH/ARC), and RFamide-related peptide-3 (RFRP-3) mRNA in the paraventricular nucleus (PVN) and dorsomedial hypothalamic nucleus. Sulpiride significantly increased plasma LH concentration and the levels of GnRH and GnRHR in the hypothalamic–pituitary unit. The abolition of dopaminergic activity resulted in a significant increase in transcript level of Kiss1 in VMH/ARC and a decrease of RFRP-3 in PVN. The study demonstrates that dopaminergic neurotransmission through D2R is involved in the regulatory pathways of GnRH and GnRHR biosynthesis in the hypothalamic–pituitary unit of anoestrous sheep, conceivably via mechanisms in which Kiss1 and RFRP-3 participate.
Collapse
|
6
|
Hutchens EG, Ramsey KA, Howard LC, Abshire MY, Patrie JT, McCartney CR. Progesterone has rapid positive feedback actions on LH release but fails to reduce LH pulse frequency within 12 h in estradiol-pretreated women. Physiol Rep 2017; 4:4/16/e12891. [PMID: 27535481 PMCID: PMC5002908 DOI: 10.14814/phy2.12891] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 07/18/2016] [Indexed: 11/24/2022] Open
Abstract
In women, progesterone suppresses luteinizing hormone (LH) (gonadotropin‐releasing hormone) pulse frequency, but how rapidly this occurs is unknown. In estradiol‐pretreated women in the late follicular phase, progesterone administration at 1800 did not slow sleep‐associated LH pulse frequency. However, mechanisms controlling LH pulse frequency may differ according to sleep status; and we thus hypothesized that progesterone acutely suppresses waking LH pulse frequency. This was a randomized, double‐blind, crossover study of LH secretory responses to progesterone versus placebo administered at 0600. We studied 12 normal women in the late follicular phase (cycle days 7–11), pretreated with 3 days of transdermal estradiol (0.2 mg/day). Subjects underwent a 24‐h blood sampling protocol (starting at 2000) and received either 100 mg oral micronized progesterone or placebo at 0600. In a subsequent menstrual cycle, subjects underwent an identical protocol except that oral progesterone was exchanged for placebo or vice versa. Changes in 10‐h LH pulse frequency were similar between progesterone and placebo. However, mean LH, LH pulse amplitude, and mean follicle‐stimulating hormone exhibited significantly greater increases with progesterone. Compared to our previous study (progesterone administered at 1800), progesterone administration at 0600 was associated with a similar increase in mean LH, but a less pronounced increase in LH pulse amplitude. We conclude that, in estradiol‐pretreated women in the late follicular phase, a single dose of progesterone does not suppress waking LH pulse frequency within 12 h, but it acutely amplifies mean LH and LH pulse amplitude – an effect that may be influenced by sleep status and/or time of day.
Collapse
Affiliation(s)
- Eleanor G Hutchens
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlottesville, Virginia Center for Research in Reproduction, University of Virginia School of Medicine, Charlottesville, Virginia
| | | | - Louisa C Howard
- College and Graduate School of Arts and Sciences, University of Virginia, Charlottesville, Virginia
| | - Michelle Y Abshire
- Center for Research in Reproduction, University of Virginia School of Medicine, Charlottesville, Virginia
| | - James T Patrie
- Department of Public Health Sciences, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Christopher R McCartney
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine, Charlottesville, Virginia Center for Research in Reproduction, University of Virginia School of Medicine, Charlottesville, Virginia
| |
Collapse
|
7
|
Ciechanowska M, Łapot M, Mateusiak K, Paruszewska E, Malewski T, Przekop F. Biosynthesis of gonadotropin-releasing hormone (GnRH) and GnRH receptor (GnRHR) in hypothalamic–pituitary unit of anoestrous and cyclic ewes. Can J Physiol Pharmacol 2017; 95:178-184. [DOI: 10.1139/cjpp-2016-0137] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study was performed to explain how the molecular processes governing the biosynthesis of gonadotropin-releasing hormone (GnRH) and GnRH receptor (GnRHR) in the hypothalamic–pituitary unit are reflected by luteinizing hormone (LH) secretion in sheep during anoestrous period and during luteal and follicular phases of the oestrous cycle. Using an enzyme-linked immunosorbent assay (ELISA), we analyzed the levels of GnRH and GnRHR in preoptic area (POA), anterior (AH) and ventromedial hypothalamus (VM), stalk–median eminence (SME), and GnRHR in the anterior pituitary gland (AP). Radioimmunoassay has also been used to define changes in plasma LH concentrations. The study provides evidence that the levels of GnRH in the whole hypothalamus of anoestrous ewes were lower than that in sheep during the follicular phase of the oestrous cycle (POA: p < 0.001, AH: p < 0.001, VM: p < 0.01, SME: p < 0.001) and not always than in luteal phase animals (POA: p < 0.05, SME: p < 0.05). It has also been demonstrated that the GnRHR amount in the hypothalamus–anterior pituitary unit, as well as LH level, in the blood in anoestrous ewes were significantly lower than those detected in animals of both cyclic groups. Our data suggest that decrease in LH secretion during the long photoperiod in sheep may be due to low translational activity of genes encoding both GnRH and GnRHR.
Collapse
Affiliation(s)
- M.O. Ciechanowska
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163 Warsaw, Poland
| | - M. Łapot
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163 Warsaw, Poland
| | - K. Mateusiak
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163 Warsaw, Poland
| | - E. Paruszewska
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163 Warsaw, Poland
| | - T. Malewski
- The Museum and Institute of Zoology, Polish Academy of Sciences, Wilcza 64, 00-679 Warsaw, Poland
| | - F. Przekop
- The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Department of Neuroendocrinology, Instytucka 3, 05-110 Jabłonna, Poland
| |
Collapse
|
8
|
Melo L, Monteiro P, Surjus R, Drum J, Wiltbank M, Sartori R. Progesterone-based fixed-time artificial insemination protocols for dairy cows: Gonadotropin-releasing hormone versus estradiol benzoate at initiation and estradiol cypionate versus estradiol benzoate at the end. J Dairy Sci 2016; 99:9227-9237. [DOI: 10.3168/jds.2016-11220] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 07/04/2016] [Indexed: 11/19/2022]
|
9
|
Ciechanowska M, Łapot M, Antkowiak B, Mateusiak K, Paruszewska E, Malewski T, Paluch M, Przekop F. Effect of short-term and prolonged stress on the biosynthesis of gonadotropin-releasing hormone (GnRH) and GnRH receptor (GnRHR) in the hypothalamus and GnRHR in the pituitary of ewes during various physiological states. Anim Reprod Sci 2016; 174:65-72. [PMID: 27629353 DOI: 10.1016/j.anireprosci.2016.09.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 08/29/2016] [Accepted: 09/06/2016] [Indexed: 10/21/2022]
Abstract
Using an ELISA assay, the levels of GnRH and GnRHR were analysed in the preoptic area (POA), anterior (AH) and ventromedial hypothalamus (VM), stalk/median eminence (SME); and GnRHR in the anterior pituitary gland (AP) of non-breeding and breeding sheep subjected to short-term or prolonged stress. The ELISA study was supplemented with an analysis of plasma LH concentration. Short-term footshock stimulation significantly increased GnRH levels in hypothalamus in both seasons. Prolonged stress elevated or decreased GnRH concentrations in the POA and the VM, respectively during anoestrus, and lowered GnRH amount in the POA-hypothalamus of follicular-phase sheep. An up-regulation of GnRHR levels was noted in both, anoestrous and follicular-phase animals. In the non-breeding period, a prolonged stress procedure increased GnRHR biosynthesis in the VM and decreased it in the SME and AP, while in the breeding time the quantities of GnRHR were significantly lower in the whole hypothalamus. In follicular-phase ewes the fluctuations of GnRH and GnRHR levels under short-term and prolonged stress were reflected in the changes of LH secretion, suggesting the existence of a direct relationship between GnRH and GnRH-R biosynthesis and GnRH/LH release in this period. The study showed that stress was capable of modulating the biosynthesis of GnRH and GnRHR; the pattern of changes was dependent upon the animal's physiological state and on the time course of stressor application. The obtained results indicate that the disturbances of gonadotropin secretion under stress conditions in sheep may be due to a dysfunction of GnRH and GnRHR biosynthetic pathways.
Collapse
Affiliation(s)
- M Ciechanowska
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163, Warsaw, Poland.
| | - M Łapot
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163, Warsaw, Poland
| | - B Antkowiak
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163, Warsaw, Poland
| | - K Mateusiak
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163, Warsaw, Poland
| | - E Paruszewska
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163, Warsaw, Poland
| | - T Malewski
- The Museum and Institute of Zoology, Polish Academy of Sciences, Wilcza 64, 00-679, Warsaw, Poland
| | - M Paluch
- The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology, Department of Pharmacology and Toxicology, Kozielska 4, 01-163, Warsaw, Poland
| | - F Przekop
- The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Department of Neuroendocrinology, Instytucka 3, 05-110, Jabłonna, Poland
| |
Collapse
|
10
|
Ciechanowska M, Łapot M, Mateusiak K, Paruszewska E, Malewski T, Krawczyńska A, Przekop F. The Central Effect of β
-Endorphin and Naloxone on The Biosynthesis of GnRH and GnRH Receptor (GnRHR) in The Hypothalamic-Pituitary Unit of Follicular-Phase Ewes. Reprod Domest Anim 2016; 51:555-61. [DOI: 10.1111/rda.12719] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 05/18/2016] [Indexed: 11/30/2022]
Affiliation(s)
- M Ciechanowska
- Department of Pharmacology and Toxicology; The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology; Warsaw Poland
| | - M Łapot
- Department of Pharmacology and Toxicology; The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology; Warsaw Poland
| | - K Mateusiak
- Department of Pharmacology and Toxicology; The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology; Warsaw Poland
| | - E Paruszewska
- Department of Pharmacology and Toxicology; The General Karol Kaczkowski Military Institute of Hygiene and Epidemiology; Warsaw Poland
| | - T Malewski
- Polish Academy of Sciences; The Museum and Institute of Zoology; Warsaw Poland
| | - A Krawczyńska
- Department of Neuroendocrinology; Polish Academy of Sciences; The Kielanowski Institute of Animal Physiology and Nutrition; Jabłonna Poland
| | - F Przekop
- Department of Neuroendocrinology; Polish Academy of Sciences; The Kielanowski Institute of Animal Physiology and Nutrition; Jabłonna Poland
| |
Collapse
|
11
|
Abstract
The endocrine hypothalamus constitutes those cells which project to the median eminence and secrete neurohormones into the hypophysial portal blood to act on cells of the anterior pituitary gland. The entire endocrine system is controlled by these peptides. In turn, the hypothalamic neuroendocrine cells are regulated by feedback signals from the endocrine glands and other circulating factors. The neuroendocrine cells are found in specific regions of the hypothalamus and are regulated by afferents from higher brain centers. Integrated function is clearly complex and the networks between and amongst the neuroendocrine cells allows fine control to achieve homeostasis. The entry of hormones and other factors into the brain, either via the cerebrospinal fluid or through fenestrated capillaries (in the basal hypothalamus) is important because it influences the extent to which feedback regulation may be imposed. Recent evidence of the passage of factors from the pars tuberalis and the median eminence casts a new layer in our understanding of neuroendocrine regulation. The function of neuroendocrine cells and the means by which pulsatile secretion is achieved is best understood for the close relationship between gonadotropin releasing hormone and luteinizing hormone, which is reviewed in detail. The secretion of other neurohormones is less rigid, so the relationship between hypothalamic secretion and the relevant pituitary hormones is more complex.
Collapse
Affiliation(s)
- I J Clarke
- Monash University, Department of Physiology, Clayton, Australia
| |
Collapse
|
12
|
Monteiro P, Borsato M, Silva F, Prata A, Wiltbank M, Sartori R. Increasing estradiol benzoate, pretreatment with gonadotropin-releasing hormone, and impediments for successful estradiol-based fixed-time artificial insemination protocols in dairy cattle. J Dairy Sci 2015; 98:3826-39. [DOI: 10.3168/jds.2014-9040] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 02/23/2015] [Indexed: 11/19/2022]
|
13
|
Painer J, Goeritz F, Dehnhard M, Hildebrandt TB, Naidenko SV, Sánchez I, Quevedo Muñoz MA, Jewgenow K. Hormone-induced luteolysis on physiologically persisting corpora lutea in Eurasian and Iberian lynx (Lynx lynx and Lynx pardinus). Theriogenology 2014; 82:557-62. [DOI: 10.1016/j.theriogenology.2014.05.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 04/04/2014] [Accepted: 05/13/2014] [Indexed: 10/25/2022]
|
14
|
Developmental programming: impact of prenatal exposure to bisphenol-A and methoxychlor on steroid feedbacks in sheep. Toxicol Appl Pharmacol 2013; 268:300-8. [PMID: 23454450 DOI: 10.1016/j.taap.2013.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 02/03/2013] [Accepted: 02/06/2013] [Indexed: 01/26/2023]
Abstract
Bisphenol-A (BPA), a polymer used in plastics manufacturing, and methoxychlor (MXC), a pesticide, are endocrine disrupting compounds with estrogenic and anti-androgenic properties. Prenatal BPA or MXC treatment induces reproductive defects in sheep with BPA causing prepubertal luteinizing hormone (LH) hypersecretion and dampening of periovulatory LH surges and MXC lengthening follicular phase and delaying the LH surge. In this study, we addressed the underlying neuroendocrine defects by testing the following hypotheses: 1) prenatal BPA, but not MXC reduces sensitivity to estradiol and progesterone negative feedback, 2) prenatal BPA, but not MXC increases pituitary responsiveness to gonadotropin releasing hormone (GnRH), and 3) prenatal BPA dampens LH surge response to estradiol positive feedback challenge while prenatal MXC delays the timing of the LH surge. Pregnant sheep were treated with either 1) 5mg/kg/day BPA (produces approximately twice the level found in human circulation, n=8), 2) 5mg/kg/day MXC (the lowest observed effect level stated in the EPA National Toxicology Program's Report; n=6), or 3) vehicle (cotton seed oil: C: n=6) from days 30 to 90 of gestation. Female offspring of these ewes were ovariectomized at 21months of age and tested for progesterone negative, estradiol negative, estradiol positive feedback sensitivities and pituitary responsiveness to GnRH. Results revealed that sensitivity to all 3 feedbacks as well as pituitary responsiveness to GnRH were not altered by either of the prenatal treatments. These findings suggest that the postpubertal reproductive defects seen in these animals may have stemmed from ovarian defects and the steroidal signals emanating from them.
Collapse
|
15
|
Whitelaw CM, Robinson JE, Hastie PM, Padmanabhan V, Evans NP. Effects of cycle stage on regionalised galanin, galanin receptors 1-3, GNRH and GNRH receptor mRNA expression in the ovine hypothalamus. J Endocrinol 2012; 212:353-61. [PMID: 22159505 DOI: 10.1530/joe-11-0352] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The neurotransmitter galanin has been implicated in the steroidogenic regulation of reproduction based on work mainly conducted in rodents. This study investigated the temporal changes in the expression of galanin and its three receptor isoforms and GNRH and GNRHR mRNA in specific hypothalamic nuclei known to be involved in the regulation of reproductive cyclicity, namely the medial pre-optic area (mPOA), the rostral mPOA/organum vasculosum of the lamina terminalis, the paraventricular nucleus and the arcuate nucleus using an ovine model. Following synchronisation of their oestrous cycles, tissues were collected from ewes at five time points: the early follicular, mid follicular (MF) and late follicular phases and the early luteal and mid luteal phases. The results indicated significant differences in regional expression of most of the genes studied, with galanin mRNA expression being highest during the MF phase at the start of the GNRH/LH surge and the expression of the three galanin receptor (GalR) isoforms and GNRH and its receptor highest during the luteal phase. These findings are consistent with a role for galanin in the positive feedback effects of oestradiol (E(2)) on GNRH secretion and a role for progesterone induced changes in the pattern of expression of GalRs in the regulation of the timing of E(2)'s positive feedback through increased sensitivity of galanin-sensitive systems to secreted galanin.
Collapse
MESH Headings
- Animals
- Arcuate Nucleus of Hypothalamus/metabolism
- Estradiol/physiology
- Estrous Cycle/metabolism
- Estrus Synchronization
- Feedback, Physiological
- Female
- Follicular Phase/metabolism
- Galanin/genetics
- Gene Expression
- Gonadotropin-Releasing Hormone/genetics
- Hypothalamus/chemistry
- Hypothalamus/metabolism
- Luteal Phase/metabolism
- Paraventricular Hypothalamic Nucleus/metabolism
- Preoptic Area/metabolism
- Progesterone/physiology
- RNA, Messenger/analysis
- Receptor, Galanin, Type 1/genetics
- Receptor, Galanin, Type 2/genetics
- Receptor, Galanin, Type 3/metabolism
- Receptors, Galanin/genetics
- Receptors, LHRH/genetics
- Sheep/metabolism
Collapse
Affiliation(s)
- Christine Margaret Whitelaw
- College of Medical, Veterinary and Life Sciences, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | | | | | | | | |
Collapse
|
16
|
Neuroendocrine regulation of GnRH release and expression of GnRH and GnRH receptor genes in the hypothalamus-pituitary unit in different physiological states. Reprod Biol 2010; 10:85-124. [PMID: 20668503 DOI: 10.1016/s1642-431x(12)60054-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
This review is focused on the relationship between neuroendocrine regulation of GnRH/LH secretion and the expression of GnRH and GnRH receptor (GnRHR) genes in the hypothalamic-pituitary unit during different physiological states of animals and under stress. Moreover, the involvement of hypothalamic GABA-ergic, Beta-endorphinergic, CRH-ergic, noradrenergic, dopaminergic and GnRH-ergic systems in the regulation of expression of the GnRH and GnRHR genes as well as secretion of GnRH/LH is analyzed. It appears that the neural mechanisms controlling GnRH gene expression in different physiological states may be distinct from those regulating GnRH/LH release. The hypothalamic GnRHR gene is probably located in different neural systems and may act in a specific way on GnRH gene expression and GnRH release.
Collapse
|
17
|
Ciechanowska M, Lapot M, Malewski T, Mateusiak K, Misztal T, Przekop F. Effects of GABA(A) receptor modulation on the expression of GnRH gene and GnRH receptor (GnRH-R) gene in the hypothalamus and GnRH-R gene in the anterior pituitary gland of follicular-phase ewes. Anim Reprod Sci 2008; 111:235-48. [PMID: 18434046 DOI: 10.1016/j.anireprosci.2008.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 02/18/2008] [Accepted: 03/14/2008] [Indexed: 11/19/2022]
Abstract
The effect of prolonged, intermittent infusion of GABA(A) receptor agonist (muscimol) or GABA(A) receptor antagonist (bicuculline) into the third cerebral ventricle on the expression of GnRH gene and GnRH-R gene in the hypothalamus and GnRH-R gene in the anterior pituitary gland was examined in follicular-phase ewes by real-time PCR. The activation or inhibition of GABA(A) receptors in the hypothalamus decreased or increased the expression of GnRH and GnRH-R genes and LH secretion, respectively. The present results indicate that the GABAergic system in the hypothalamus of follicular-phase ewes may suppress, via hypothalamic GABA(A) receptors, the expression of GnRH and GnRH-R genes in this structure. The decrease or increase of GnRH-R mRNA in the anterior pituitary gland and LH secretion in the muscimol- or bicuculline-treated ewes, respectively, is probably a consequence of parallel changes in the release of GnRH from the hypothalamus activating GnRH-R gene expression. It is suggested that GABA acting through the GABA(A) receptor mechanism on the expression of GnRH gene and GnRH-R gene in the hypothalamus may be involved in two processes: the biosynthesis of GnRH and the release of this neurohormone in the hypothalamus.
Collapse
Affiliation(s)
- Magdalena Ciechanowska
- The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Warsaw, Poland.
| | | | | | | | | | | |
Collapse
|
18
|
Abstract
Comprehensive studies have provided a clear understanding of the effects of gonadal steroids on the secretion of gonadotropin releasing hormone (GnRH), but some inconsistent results exist with regard to effects on synthesis. It is clear that regulation of both synthesis and the secretion of GnRH are effected by neurotransmitter systems in the brain. Thus, steroid regulation of GnRH synthesis and secretion can be direct, but the predominant effects are transmitted through steroid-responsive neuronal systems in various parts of the brain. There is also emerging evidence of direct effects on GnRH cells. Overriding effects on synthesis and secretion of GnRH can be observed during aging, in undernutrition and under stressful situations; these involve various neuronal systems, which may have serial or parallel effects on GnRH cells. The effect of aging is accompanied by changes in GnRH synthesis, but comprehensive studies of synthesis during undernutrition and stress are less well documented. Altered GnRH and gonadotropin secretion that occurs in seasonal breeding animals and during the pubertal transition is not generally accompanied by changes in GnRH synthesis. Secretion of GnRH from the brain is a reflection of the inherent function of GnRH cells and the inputs that integrate all of the central regulatory elements. Ultimately, the pattern of secretion dictates the reproductive status of the organism. In order to fully understand the central mechanisms that control reproduction, more extensive studies are required on the neuronal circuitry that provides input to GnRH cells.
Collapse
Affiliation(s)
- Iain J Clarke
- Prince Henry's Institute of Medical Research, P.O. Box 5152, Clayton 3168, Australia.
| | | |
Collapse
|
19
|
An BS, Choi JH, Choi KC, Leung PCK. Differential role of progesterone receptor isoforms in the transcriptional regulation of human gonadotropin-releasing hormone I (GnRH I) receptor, GnRH I, and GnRH II. J Clin Endocrinol Metab 2005; 90:1106-13. [PMID: 15562029 DOI: 10.1210/jc.2004-0318] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Hypothalamic GnRH is a decapeptide that plays a pivotal role in mammalian reproduction by stimulating the synthesis and secretion of gonadotropins via binding to the GnRH receptor on the pituitary gonadotropins. It is hypothesized that sex steroids may regulate GnRH I (a classical form of GnRH), GnRH II (a second form of GnRH), and GnRH I receptor (GnRHRI) at the transcriptional level in target tissues. Thus, in the present study a role for progesterone (P4) in the regulation of GnRH I, GnRH II, and GnRHRI was investigated using a human neuronal medulloblastoma cell line (TE671) as an in vitro model. The cells were transfected with human GnRHRI promoter-luciferase constructs, and promoter activities were analyzed after P4 treatment by luciferase and beta-galactosidase assay. The mRNA levels of GnRH I and GnRH II were analyzed by RT-PCR. Treatment of TE671 cells with P4 resulted in a decrease in GnRHRI promoter activity compared with the control level in a dose- and time-dependent manner. Cotreatment of these cells with RU486, an antagonist of P4, reversed P4-induced inhibition of GnRHRI promoter activity, suggesting that the P4 effect is mediated by P4 receptor (PR). In the cells transfected with a full-length of PR A- or PR B-expressing vector, overexpression of PR A increased the sensitivity toward P4 in an inhibition of GnRHRI promoter, whereas PR B increased transcriptional activity of GnRHRI promoter in the presence of P4. However, PR B itself did not act as a transcriptional activator of GnRHRI promoter. Because TE671 cells have been recently demonstrated to express and synthesize two forms of GnRHs, we also investigated the regulation of GnRH mRNAs by P4. In the present study, P4 increased GnRH I mRNA levels in a time- and dose-dependent manner. This stimulatory effect of P4 in the regulation of GnRH I mRNAs was significantly attenuated by RU486, whereas no significant difference in the expression level of GnRH II was observed with P4 or RU496. Interestingly, although the expression level of PR B was low compared with that of PR A, P4 action on the GnRH I gene was mediated by PR B. In conclusion, these results indicate that P4 is a potent regulator of GnRHRI at the transcriptional level as well as GnRH I mRNA. This distinct effect of P4 on the GnRH system may be derived from different pathways through PR A or PR B.
Collapse
Affiliation(s)
- Beum-Soo An
- Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, British Columbia, Canada V6H 3V5
| | | | | | | |
Collapse
|
20
|
Neuroanatomical organization of gonadotropin-releasing hormone neurons during the oestrus cycle in the ewe. BMC Neurosci 2004; 5:46. [PMID: 15555074 PMCID: PMC535905 DOI: 10.1186/1471-2202-5-46] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2004] [Accepted: 11/22/2004] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND During the preovulatory surge of gonadotropin-releasing hormone (GnRH), a very large amount of the peptide is released in the hypothalamo-hypophyseal portal blood for 24-36H00. To study whether this release is linked to a modification of the morphological organization of the GnRH-containing neurons, i.e. morphological plasticity, we conducted experiments in intact ewes at 4 different times of the oestrous cycle (before the expected LH surge, during the LH surge, and on day 8 and day 15 of the subsequent luteal phase). The cycle stage was verified by determination of progesterone and LH concentrations in the peripheral blood samples collected prior to euthanasia. RESULTS The distribution of GnRH-containing neurons throughout the preoptic area around the vascular organ of the lamina terminalis was studied following visualisation using immunohistochemistry. No difference was observed in the staining intensity for GnRH between the different groups. Clusters of GnRH-containing neurons (defined as 2 or more neurons being observed in close contact) were more numerous during the late follicular phase (43 +/- 7) than during the luteal phase (25 +/- 6), and the percentage of clusters was higher during the beginning of the follicular phase than during the luteal phase. There was no difference in the number of labelled neurons in each group. CONCLUSIONS These results indicate that the morphological organization of the GnRH-containing neurons in ewes is modified during the follicular phase. This transitory re-organization may contribute to the putative synchronization of these neurons during the surge. The molecular signal inducing this plasticity has not yet been identified, but oestradiol might play an important role, since in sheep it is the only signal which initiates the GnRH preovulatory surge.
Collapse
|