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Gurule S, Sustaita-Monroe J, Padmanabhan V, Cardoso R. Developmental programming of the neuroendocrine axis by steroid hormones: Insights from the sheep model of PCOS. Front Endocrinol (Lausanne) 2023; 14:1096187. [PMID: 36755919 PMCID: PMC9899912 DOI: 10.3389/fendo.2023.1096187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 01/06/2023] [Indexed: 01/25/2023] Open
Abstract
The reproductive neuroendocrine system is a key target for the developmental programming effects of steroid hormones during early life. While gonadal steroids play an important role in controlling the physiological development of the neuroendocrine axis, human fetuses are susceptible to adverse programming due to exposure to endocrine disrupting chemicals with steroidal activity, inadvertent use of contraceptive pills during pregnancy, as well as from disease states that result in abnormal steroid production. Animal models provide an unparalleled resource to understand the effects of steroid hormones on the development of the neuroendocrine axis and their role on the developmental origins of health and disease. In female sheep, exposure to testosterone (T) excess during fetal development results in an array of reproductive disorders that recapitulate those seen in women with polycystic ovary syndrome (PCOS), including disrupted neuroendocrine feedback mechanisms, increased pituitary responsiveness to gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) hypersecretion, functional hyperandrogenism, multifollicular ovarian morphology, and premature reproductive failure. Similar to a large proportion of women with PCOS, these prenatally T-treated sheep also manifest insulin resistance and cardiovascular alterations, including hypertension. This review article focuses on the effects of prenatal androgens on the developmental programming of hypothalamic and pituitary alterations in the sheep model of PCOS phenotype, centering specifically on key neurons, neuropeptides, and regulatory pathways controlling GnRH and LH secretion. Insights obtained from the sheep model as well as other animal models of perinatal androgen excess can have important translational relevance to treat and prevent neuroendocrine dysfunction in women with PCOS and other fertility disorders.
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Affiliation(s)
- Sara Gurule
- Department of Animal Science, Texas A&M University, College Station, TX, United States
| | | | | | - Rodolfo Cardoso
- Department of Animal Science, Texas A&M University, College Station, TX, United States
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Zhao X, Erickson M, Mohammed R, Kentner AC. Maternal immune activation accelerates puberty initiation and alters mechanical allodynia in male and female C57BL6/J mice. Dev Psychobiol 2022; 64:e22278. [DOI: 10.1002/dev.22278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/13/2022] [Accepted: 03/09/2022] [Indexed: 12/17/2022]
Affiliation(s)
- Xin Zhao
- School of Arts & Sciences, Health Psychology Program Massachusetts College of Pharmacy and Health Sciences Boston Massachusetts USA
| | - Mary Erickson
- School of Arts & Sciences, Health Psychology Program Massachusetts College of Pharmacy and Health Sciences Boston Massachusetts USA
| | - Ruqayah Mohammed
- School of Arts & Sciences, Health Psychology Program Massachusetts College of Pharmacy and Health Sciences Boston Massachusetts USA
| | - Amanda C. Kentner
- School of Arts & Sciences, Health Psychology Program Massachusetts College of Pharmacy and Health Sciences Boston Massachusetts USA
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Suetomi Y, Tatebayashi R, Sonoda S, Munetomo A, Matsuyama S, Inoue N, Uenoyama Y, Takeuchi Y, Tsukamura H, Ohkura S, Matsuda F. Establishment of immortalised cell lines derived from female Shiba goat KNDy and GnRH neurones. J Neuroendocrinol 2020; 32:e12857. [PMID: 32432378 DOI: 10.1111/jne.12857] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 04/10/2020] [Accepted: 04/20/2020] [Indexed: 12/27/2022]
Abstract
Kisspeptin plays a critical role in governing gonadotrophin-releasing hormone (GnRH)/gonadotrophin secretion and subsequent reproductive function in mammals. The hypothalamic arcuate nucleus (ARC) kisspeptin neurones, which co-express neurokinin B (NKB) and dynorphin A (Dyn) and are referred to as KNDy neurones, are considered to be involved in GnRH generation. The present study aimed to establish cell lines derived from goat KNDy and GnRH neurones. Primary-cultured cells of female Shiba goat foetal hypothalamic ARC and preoptic area (POA) tissues were immortalised with the infection of lentivirus containing the simian virus 40 large T-antigen gene. Clones of the immortalised cells were selected by the gene expression of a neuronal marker, and then the neurone-derived cell clones were further selected by the gene expression of KNDy or GnRH neurone markers. As a result, we obtained a KNDy neurone cell line (GA28) from the ARC, as well as two GnRH neurone cell lines (GP11 and GP31) from the POA. Immunocytochemistry revealed the expression of kisspeptin, NKB and Dyn in GA28 cells, as well as GnRH in GP11 and GP31 cells. GnRH secretion from GP11 and GP31 cells into the media was confirmed by an enzyme immunoassay. Moreover, kisspeptin challenge increased intracellular Ca2+ levels in subsets of both GP11 and GP31 cells. Kisspeptin mRNA expression in GA28 cells, which expressed the oestrogen receptor alpha gene, was significantly reduced by 17β-oestradiol treatment. Furthermore, the transcriptional core promoter and repressive regions of the goat NKB gene were detected using GA28 cells. In conclusion, we have established goat KNDy and GnRH neurone cell lines that could be used to analyse molecular and cellular mechanisms regulating KNDy and GnRH neurones in vitro, facilitating the clarification of reproductive neuroendocrine mechanisms in ruminants.
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Affiliation(s)
- Yuta Suetomi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Ryoki Tatebayashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Shuhei Sonoda
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Arisa Munetomo
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Shuichi Matsuyama
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Naoko Inoue
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Yoshihisa Uenoyama
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Yukari Takeuchi
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Hiroko Tsukamura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Satoshi Ohkura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Fuko Matsuda
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
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Faykoo-Martinez M, Monks DA, Zovkic IB, Holmes MM. Sex- and brain region-specific patterns of gene expression associated with socially-mediated puberty in a eusocial mammal. PLoS One 2018; 13:e0193417. [PMID: 29474488 PMCID: PMC5825099 DOI: 10.1371/journal.pone.0193417] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 02/09/2018] [Indexed: 12/13/2022] Open
Abstract
The social environment can alter pubertal timing through neuroendocrine mechanisms that are not fully understood; it is thought that stress hormones (e.g., glucocorticoids or corticotropin-releasing hormone) influence the hypothalamic-pituitary-gonadal axis to inhibit puberty. Here, we use the eusocial naked mole-rat, a unique species in which social interactions in a colony (i.e. dominance of a breeding female) suppress puberty in subordinate animals. Removing subordinate naked mole-rats from this social context initiates puberty, allowing for experimental control of pubertal timing. The present study quantified gene expression for reproduction- and stress-relevant genes acting upstream of gonadotropin-releasing hormone in brain regions with reproductive and social functions in pre-pubertal, post-pubertal, and opposite sex-paired animals (which are in various stages of pubertal transition). Results indicate sex differences in patterns of neural gene expression. Known functions of genes in brain suggest stress as a key contributing factor in regulating male pubertal delay. Network analysis implicates neurokinin B (Tac3) in the arcuate nucleus of the hypothalamus as a key node in this pathway. Results also suggest an unappreciated role for the nucleus accumbens in regulating puberty.
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Affiliation(s)
| | - D. Ashley Monks
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Iva B. Zovkic
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Melissa M. Holmes
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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Matsuda F, Nakatsukasa K, Suetomi Y, Naniwa Y, Ito D, Inoue N, Wakabayashi Y, Okamura H, Maeda KI, Uenoyama Y, Tsukamura H, Ohkura S. The luteinising hormone surge-generating system is functional in male goats as in females: involvement of kisspeptin neurones in the medial preoptic area. J Neuroendocrinol 2015; 27:57-65. [PMID: 25367275 DOI: 10.1111/jne.12235] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 10/28/2014] [Accepted: 10/28/2014] [Indexed: 12/21/2022]
Abstract
A luteinising hormone (LH) surge is fundamental to the induction of ovulation in mammalian females. The administration of a preovulatory level of oestrogen evokes an LH surge in ovariectomised females, whereas the response to oestrogen in castrated males differs among species; namely, the LH surge-generating system is sexually differentiated in some species (e.g. rodents and sheep) but not in others (e.g. primates). In the present study, we aimed to determine whether there is a functional LH surge-generating system in male goats, and whether hypothalamic kisspeptin neurones in male goats are involved in the regulation of surge-like LH secretion. By i.v. infusion of oestradiol (E2; 6 μg/h) for 16 h, a surge-like LH increase occurred in both castrated male and ovariectomised female goats, although the mean peak LH concentration was lower and the mean peak of the LH surge was later in males compared to females. Dual staining with KISS1 in situ hybridisation and c-Fos immunohistochemistry revealed that E2 treatment significantly increased c-Fos expression in the medial preoptic area (mPOA) KISS1 cells in castrated males, as well as ovariectomised females. By contrast, dual-labelled cells were scarcely detected in the arcuate nucleus (ARC) after E2 treatment in both sexes. These data suggest that kisspeptin neurones in the mPOA, but not those in the ARC, are involved in the induction of surge-like LH secretion in both male and female goats. In summary, our data show that the mechanism that initiates the LH surge in response to oestrogen, the mPOA kisspeptin neurones, is functional in male goats. Thus, sexual differentiation of the LH surge-generating system would not be applicable to goats.
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Affiliation(s)
- F Matsuda
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, Japan
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Rose JL, Hamlin AS, Scott CJ. Sex differences in the expression of estrogen receptor alpha within noradrenergic neurons in the sheep brain stem. Domest Anim Endocrinol 2014; 49:6-13. [PMID: 25010022 DOI: 10.1016/j.domaniend.2014.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 04/15/2014] [Accepted: 04/17/2014] [Indexed: 01/08/2023]
Abstract
In female sheep, high levels of estrogen exert a positive feedback action on gonadotropin releasing hormone (GnRH) secretion to stimulate a surge in luteinizing hormone (LH) secretion. Part of this action appears to be via brain stem noradrenergic neurons. By contrast, estrogen action in male sheep has a negative feedback action to inhibit GnRH and LH secretion. To investigate whether part of this sex difference is due to differences in estrogen action in the brain stem, we tested the hypothesis that the distribution of estrogen receptor α (ERα) within noradrenergic neurons in the brain stem differs between rams and ewes. To determine the distribution of ERα, we used double-label fluorescence immunohistochemistry for dopamine β-Hydroxylase, as a marker for noradrenergic and adrenergic cells, and ERα. In the ventrolateral medulla (A1 region), most ERα-immunoreactive (-ir) cells were located in the caudal part of the nucleus. Overall, there were more ERα-ir cells in rams than ewes, but the proportion of double-labeled cells was did not differ between sexes. Much greater numbers of ERα-ir cells were found in the nucleus of the solitary tract (A2 region), but <10% were double labeled and there were no sex differences. The majority of ERα-labeled cells in this nucleus was located in the more rostral areas. ERα-labeled cells were found in several rostral brain stem regions but none of these were double labeled and so were not quantified. Because there was no sex difference in the number of ERα-ir cells in the brain stem that were noradrenergic, the sex difference in the action of estrogen on gonadotropin secretion in sheep is unlikely to involve actions on brain stem noradrenergic cells.
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Affiliation(s)
- J L Rose
- School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, North South Wales, Australia; Graham Centre for Agricultural Innovation, Charles Sturt University and NSW Department of Primary Industries, Australia
| | - A S Hamlin
- School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, North South Wales, Australia
| | - C J Scott
- School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, North South Wales, Australia; Graham Centre for Agricultural Innovation, Charles Sturt University and NSW Department of Primary Industries, Australia.
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Goodman RL, Coolen LM, Lehman MN. A role for neurokinin B in pulsatile GnRH secretion in the ewe. Neuroendocrinology 2014; 99:18-32. [PMID: 24008670 PMCID: PMC3976461 DOI: 10.1159/000355285] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 08/24/2013] [Indexed: 01/15/2023]
Abstract
The recent description of infertility in humans with loss-of-function mutations in genes for neurokinin B (NKB) or its receptor (NK3R) has focused attention on the importance of this tachykinin in the control of GnRH secretion. In a number of species, NKB neurons in the arcuate nucleus also produce two other neuropeptides implicated in the control of GnRH secretion: (1) kisspeptin, which is also essential for fertility in humans, and (2) dynorphin, an inhibitory endogenous opioid peptide. A number of characteristics of this neuronal population led to the hypothesis that they may be responsible for driving synchronous release of GnRH during episodic secretion of this hormone, and there is now considerable evidence to support this hypothesis in sheep and goats. In this article, we briefly review the history of work on the NKB system in sheep and then review the anatomy of NKB signaling in the ewe. We next describe evidence from a number of species that led to development of a model for the role of these neurons in episodic GnRH secretion. Finally, we discuss recent experiments in sheep and goats that tested this hypothesis and led to a modified version of the model, and then broaden our focus to briefly consider the possible roles of NKB in other species and systems.
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Affiliation(s)
- Robert L Goodman
- Department of Physiology and Pharmacology, West Virginia University, Morgantown, W.Va., USA
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Fergani C, Routly JE, Jones DN, Pickavance LC, Smith RF, Dobson H. Kisspeptin, c-Fos and CRFR type 2 expression in the preoptic area and mediobasal hypothalamus during the follicular phase of intact ewes, and alteration after LPS. Physiol Behav 2013; 110-111:158-68. [PMID: 23313561 DOI: 10.1016/j.physbeh.2012.12.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 12/29/2012] [Indexed: 11/29/2022]
Abstract
Increasing estradiol concentrations during the late follicular phase stimulate sexual behavior and the GnRH/LH surge, and it is known that kisspeptin signaling is essential for the latter. Administration of LPS can block these events, but the mechanism involved is unclear. We examined brain tissue from intact ewes to determine: i) which regions are activated with respect to sexual behavior, the LH surge and LPS administration, ii) the location and activation pattern of kisspeptin cells in control and LPS treated animals, and iii) whether CRFR type 2 is involved in such disruptive mechanisms. Follicular phases were synchronized with progesterone vaginal pessaries and control animals were killed at 0 h, 16 h, 31 h or 40 h (n=4-6/group) after progesterone withdrawal (time zero). At 28 h, other animals received endotoxin (LPS; 100 ng/kg) and were subsequently killed at 31 h or 40 h (n=5/group). LH surges only occurred in control ewes, during which there was a marked increase in c-Fos expression within the ventromedial nucleus (VMN), arcuate nucleus (ARC), and medial preoptic area (mPOA), as well as an increase in the percentage of kisspeptin cells co-expressing c-Fos in the ARC and mPOA compared to animals sacrificed at all other times. Expression of c-Fos also increased in the bed nucleus of the stria terminalis (BNST) in animals just before the expected onset of sexual behavior. However, LPS treatment increased c-Fos expression within the VMN, ARC, mPOA and diagonal band of broca (dBb), along with CRFR type 2 immunoreactivity in the lower part of the ARC and median eminence (ME), compared to controls. Furthermore, the percentage of kisspeptin cells co-expressing c-Fos was lower in the ARC and mPOA. Thus, we hypothesize that in intact ewes, the BNST is involved in the initiation of sexual behavior while the VMN, ARC, and mPOA as well as kisspeptin cells located in the latter two areas are involved in estradiol positive feedback only during the LH surge. By contrast, disruption of sexual behavior and the LH surge after LPS involves cells located in the VMN, ARC, mPOA and dBb, as well as cells containing CRFR type 2 in the lower part of the ARC and ME, and is accompanied by inhibition of kisspeptin cell activation in both the ARC and mPOA.
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Affiliation(s)
- C Fergani
- School of Veterinary Science, University of Liverpool, Leahurst Campus, Neston, Wirral CH64 7TE, UK.
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Jansen HT, Hershey J, Mytinger A, Foster DL, Padmanabhan V. Developmental programming: reproductive endocrinopathies in the adult female sheep after prenatal testosterone treatment are reflected in altered ontogeny of GnRH afferents. Endocrinology 2011; 152:4288-97. [PMID: 21933866 PMCID: PMC3199006 DOI: 10.1210/en.2011-0117] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The GnRH system represents a useful model of long-term neural plasticity. An unexplored facet of this plasticity relates to the ontogeny of GnRH neural afferents during critical periods when the hypothalamic-pituitary-gonadal axis is highly susceptible to perturbation by sex steroids. Sheep treated with testosterone (T) in utero exhibit profound reproductive neuroendocrine dysfunctions during their lifespan. The current study tested the hypothesis that these changes are associated with alterations in the normal ontogeny of GnRH afferents and glial associations. Adult pregnant sheep (n=50) were treated with vehicle [control (CONT)] or T daily from gestational day (GD)30 to GD90. CONT and T fetuses (n=4-6/treatment per age group) were removed by cesarean section on GD90 and GD140 and the brains frozen at -80°C. Brains were also collected from CONT and T females at 20-23 wk (prepubertal), 10 months (normal onset of puberty and oligo-anovulation), and 21 months (oligo-anovulation in T females). Tissue was analyzed for GnRH immunoreactivity (ir), total GnRH afferents (Synapsin-I ir), glutamate [vesicular glutamate transporter-2 (VGLUT2)-ir], and γ-aminobutyric acid [GABA, vesicular GABA transporter (VGAT)-ir] afferents and glial associations (glial fibrillary acidic protein-ir) with GnRH neurons using optical sectioning techniques. The results revealed that: 1) GnRH soma size was slightly reduced by T, 2) the total (Synapsin-I) GnRH afferents onto both somas and dendrites increased significantly with age and was reduced by T, 3) numbers of both VGAT and VGLUT inputs increased significantly with age and were also reduced by T, and 4) glial associations with GnRH neurons were reduced (<10%) by T. Together, these findings reveal a previously unknown developmental plasticity in the GnRH system of the sheep. The altered developmental trajectory of GnRH afferents after T reinforces the notion that prenatal programming plays an important role in the normal development of the reproductive neuroendocrine axis.
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Affiliation(s)
- Heiko T Jansen
- Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology, Washington State University, P.O. Box 646520, Pullman, Washington 99164-6520, USA.
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Yeo SH, Herbison AE. Projections of arcuate nucleus and rostral periventricular kisspeptin neurons in the adult female mouse brain. Endocrinology 2011; 152:2387-99. [PMID: 21486932 DOI: 10.1210/en.2011-0164] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The important role of kisspeptin neurons in the regulation of GnRH neuron activity is now well accepted. However, the ways in which kisspeptin neurons located in the arcuate nucleus (ARN) and rostral periventricular area of the third ventricle (RP3V) control GnRH neurons are poorly understood. The present study used anterograde and retrograde tracing techniques to establish the neuronal projection patterns of kisspeptin cell populations in the female mouse brain. Anterograde tracing studies revealed that kisspeptin neurons in the ARN innervated a wide number of hypothalamic and associated limbic region nuclei, whereas RP3V kisspeptin neurons projected to a smaller number of mostly medially located hypothalamic nuclei. Retrograde tracing confirmed a major projection of RP3V kisspeptin neurons to the ARN and showed that kisspeptin neurons located in the rostral half of the ARN projected to the rostral preoptic area. Peripheral administration of Fluorogold was found to label the majority of GnRH neurons but no kisspeptin neurons. Together, these studies highlight the complexity of the brain kisspeptin neuronal system and indicate that both ARN and RP3V kisspeptin neurons participate in a variety of limbic functions. In relation to the GnRH neuronal network, these investigations demonstrate that, alongside the RP3V kisspeptin cells, rostral ARN kisspeptin neurons may also project to GnRH neuron cell bodies. However, no kisspeptin neurons innervate GnRH nerve terminals in the external layer of the median eminence. These studies provide a neuroanatomical framework for the further elucidation of the functions of the ARN and RP3V kisspeptin neuron populations.
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Affiliation(s)
- Shel-Hwa Yeo
- Centre for Neuroendocrinology, Department of Physiology, University of Otago School of Medical Sciences, Dunedin 9054, New Zealand
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Lehman MN, Ladha Z, Coolen LM, Hileman SM, Connors JM, Goodman RL. Neuronal plasticity and seasonal reproduction in sheep. Eur J Neurosci 2011; 32:2152-64. [PMID: 21143669 DOI: 10.1111/j.1460-9568.2010.07530.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Seasonal reproduction represents a naturally occurring example of functional plasticity in the adult brain as it reflects changes in neuroendocrine pathways controlling gonadotropin-releasing hormone (GnRH) secretion and, in particular, the responsiveness of GnRH neurons to estradiol negative feedback. Structural plasticity within this neural circuitry may, in part, be responsible for seasonal switches in the negative feedback control of GnRH secretion that underlie annual reproductive transitions. We review evidence for structural changes in the circuitry responsible for seasonal inhibition of GnRH secretion in sheep. These include changes in synaptic inputs onto GnRH neurons, as well as onto dopamine neurons in the A15 cell group, a nucleus that plays a key role in estradiol negative feedback. We also present preliminary data suggesting a role for neurotrophins and neurotrophin receptors as an early mechanistic step in the plasticity that accompanies seasonal reproductive transitions in sheep. Finally, we review recent evidence suggesting that kisspeptin cells of the arcuate nucleus constitute a critical intermediary in the control of seasonal reproduction. Although a majority of the data for a role of neuronal plasticity in seasonal reproduction has come from the sheep model, the players and principles are likely to have relevance for reproduction in a wide variety of vertebrates, including humans, and in both health and disease.
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Affiliation(s)
- Michael N Lehman
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, N6A 5C1, Canada.
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Lehman MN, Coolen LM, Goodman RL. Minireview: kisspeptin/neurokinin B/dynorphin (KNDy) cells of the arcuate nucleus: a central node in the control of gonadotropin-releasing hormone secretion. Endocrinology 2010; 151:3479-89. [PMID: 20501670 PMCID: PMC2940527 DOI: 10.1210/en.2010-0022] [Citation(s) in RCA: 527] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recently, a subset of neurons was identified in the arcuate nucleus of the hypothalamus that colocalize three neuropeptides, kisspeptin, neurokinin B, and dynorphin, each of which has been shown to play a critical role in the central control of reproduction. Growing evidence suggests that these neurons, abbreviated as the KNDy subpopulation, are strongly conserved across a range of species from rodents to humans and play a key role in the physiological regulation of GnRH neurons. KNDy cells are a major target for steroid hormones, form a reciprocally interconnected network, and have direct projections to GnRH cell bodies and terminals, features that position them well to convey steroid feedback control to GnRH neurons and potentially serve as a component of the GnRH pulse generator. In addition, recent work suggests that alterations in KNDy cell peptides may underlie neuroendocrine defects seen in clinical reproductive disorders such as polycystic ovarian syndrome. Taken together, this evidence suggests a key role for the KNDy subpopulation as a focal point in the control of reproductive function in health and disease.
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Affiliation(s)
- Michael N Lehman
- Department of Anatomy and Cell Biology, Medical Sciences Building, University of Western Ontario, London, Ontario, Canada.
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Backholer K, Smith J, Clarke IJ. Melanocortins may stimulate reproduction by activating orexin neurons in the dorsomedial hypothalamus and kisspeptin neurons in the preoptic area of the ewe. Endocrinology 2009; 150:5488-97. [PMID: 19819961 DOI: 10.1210/en.2009-0604] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To further test the hypothesis that melanocortins stimulate the reproductive axis, we treated ewes with melanocortin agonist (MTII) in the luteal phase of the estrous cycle and during seasonal anestrus. Lateral ventricular infusion of MTII (10 microg/h) during the luteal phase increased LH secretion. Retrograde neuronal tracing in the brain showed few proopiomelanocortin or kisspeptin cells in the arcuate nucleus, but more than 70% of kisspeptin cells in the dorsolateral preoptic area (POA), projecting to the ventromedial POA in which GnRH cells are located. MTII infusion (20 h) was repeated in luteal phase ewes and brains were harvested to measure gene expression of preproorexin and kisspeptin. Expression of orexin in the dorsomedial hypothalamus and kisspeptin in the POA was up-regulated by MTII treatment and Kiss1 in the arcuate nucleus was down-regulated. Seasonally anestrous ewes were progesterone primed and then treated (lateral ventricular) with MTII (10 microg/h) or vehicle for 30 h, and blood samples were collected every 2 h from 4 h before infusion until 6 h afterward to monitor acute response in terms of LH levels. A rise in basal LH levels was seen, but samples collected around the time of the predicted LH surge did not indicate that an ovulatory event occurred. We conclude that melanocortins are positive regulators of the reproductive neuroendocrine system, but treatment with melanocortins does not fully overcome seasonal acyclicity. The stimulatory effect of melanocortin in the luteal phase of the estrous cycle may be via the activation of kisspeptin cells in the POA and/or orexin cells in the dorsomedial hypothalamus.
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Affiliation(s)
- Kathryn Backholer
- Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
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14
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Pereira A, Rawson J, Jakubowska A, Clarke IJ. Estradiol-17beta-responsive A1 and A2 noradrenergic cells of the brain stem project to the bed nucleus of the stria terminalis in the ewe brain: a possible route for regulation of gonadotropin releasing hormone cells. Neuroscience 2009; 165:758-73. [PMID: 19857554 DOI: 10.1016/j.neuroscience.2009.10.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 10/13/2009] [Accepted: 10/14/2009] [Indexed: 11/16/2022]
Abstract
We have studied brain stem cells in the ewe brain that project to the bed nucleus of the stria terminalis (BNST) and determined if these cells are activated by estradiol-17beta. This would predicate an indirect role in the estradiol-17beta regulation of gonadotropin releasing hormone (GnRH) cells, since these receive input from the BNST. Ovariectomized ewes received 50 mug estradiol-17beta benzoate (i.m.) 1 h prior to brain collection, so that activated cells could be identified by Fos immunohistochemistry. Retrograde tracer (FluoroGold; FG), was injected into the three divisions of the BNST and labeled cells were mapped to the A1 and A2 regions and the parabrachial nucleus (PBN) of the brain stem. With FG injection into the dorsal and lateral BNST, all FG-containing cells in the caudal A1 and 45% of those in A2 stained for dopamine-beta-hydroxylase (DBH), indicating noradrenergic type. No FG-labelled cells in the PBN were DBH-positive. In A1 and A2 respectively, 42% and 46% of FG-labelled cells were Fos-positive, with no double-labeling in cells of the PBN. In ewes receiving FG injections into the ventral BNST, estrogen receptor (ER)alpha-immunoreactive nuclei were found in 82% of A1-FG labeled and 38% of A2-FG labeled cells. No FG-labelled cells of the PBN were ERalpha-positive. Anterograde tracing from A1 with microruby injection identified projections to the PBN, BNST and preoptic area (POA). Thus, A1 and A2 noradrenergic neurons project to the BNST in the ewe brain, express ERalpha and are activated by estradiol-17beta. These noradrenergic, estrogen-responsive cells may provide indirect input to GnRH cells, via the BNST.
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Affiliation(s)
- A Pereira
- Department of Physiology, Building 13F, Monash University, Clayton, VIC 3800, Australia
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15
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Tillet Y, Picard S, Franceschini I. Les neuropeptides hypothalamiques dans le contrôle des neurones à GnRH. Étude neuroanatomique chez la brebis. ACTA ACUST UNITED AC 2009; 203:19-28. [DOI: 10.1051/jbio:2009003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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16
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Gorton LM, Mahoney MM, Magorien JE, Lee TM, Wood RI. Estrogen receptor immunoreactivity in late-gestation fetal lambs. Biol Reprod 2009; 80:1152-9. [PMID: 19164175 DOI: 10.1095/biolreprod.108.073189] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Prenatal androgens masculinize postnatal reproductive neuroendocrine function and behavior in sheep. Testosterone treatment of pregnant ewes during midgestation masculinizes sexual behavior and luteinizing hormone secretion in female lambs, presumably in part via aromatization and estrogen receptor (ESR) binding in the brain. We hypothesized that male and female sheep also differ in the number and distribution of ESR-containing neurons. If so, ESR expression should be sensitive to prenatal hormones delivered exogenously or in situ. ESR alpha (ESR1) was compared by immunocytochemistry in male and female lambs at the end of gestation, as well as in fetal females exposed prenatally to testosterone or dihydrotestosterone. ESR1-positive neurons were abundant in the posteromedial bed nucleus of the stria terminalis (BSTpm), medial preoptic area (MPOA), posterior medial amygdaloid nucleus (MeP), amygdalohippocampal area (AHi), ventromedial hypothalamic nuclei (VMH), and arcuate hypothalamic nuclei (ARC). In females, the ARC had the largest number of stained cells (mean +/- SEM, 475.6 +/- 57.4 cells/0.173 mm(2)), while staining intensity was greatest in the MPOA (mean +/- SEM gray level, 31.3 +/- 5.3). The mean +/- SEM integrated gray level (IGL) was high in the ARC (0.63 +/- 0.13) and in the MPOA (0.51 +/- 0.08). The mean +/- SEM IGL was low in the MeP (0.31 +/- 0.10) and in the BSTpm (0.21 +/- 0.06), while it was intermediate in the AHi (0.36 +/- 0.10) and in the VMH (0.37 +/- 0.07). ESR immunostaining was not significantly different in male and female fetal lambs, nor in females fetuses exposed prenatally to androgens (P > 0.05). However, ESR1 staining was significantly increased in the ARC, MPOA, and AHi of adult rams vs. adult ewes. These results suggest that brain ESR immunoreactivity in fetal lambs is unlikely to account for postnatal sex differences in reproductive function. Instead, sex differences in ESR emerge postnatally.
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Affiliation(s)
- Lori M Gorton
- Department of Cell and Neurobiology, Keck School of Medicine at the University of Southern California, Los Angeles, California 90033, USA
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17
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Kauffman AS. Sexual differentiation and the Kiss1 system: hormonal and developmental considerations. Peptides 2009; 30:83-93. [PMID: 18644414 PMCID: PMC2631352 DOI: 10.1016/j.peptides.2008.06.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 06/04/2008] [Accepted: 06/05/2008] [Indexed: 12/30/2022]
Abstract
The nervous system (both central and peripheral) is anatomically and physiologically differentiated between the sexes, ranging from gender-based differences in the cerebral cortex to motoneuron number in the spinal cord. Although genetic factors may play a role in the development of some sexually differentiated traits, most identified sex differences in the brain and behavior are produced under the influence of perinatal sex steroid signaling. In many species, the ability to display an estrogen-induced luteinizing hormone (LH) surge is sexually differentiated, yet the specific neural population(s) that allows females but not males to display such estrogen-mediated "positive feedback" has remained elusive. Recently, the Kiss1/kisspeptin system has been implicated in generating the sexually dimorphic circuitry underlying the LH surge. Specifically, Kiss1 gene expression and kisspeptin protein levels in the anteroventral periventricular (AVPV) nucleus of the hypothalamus are sexually differentiated, with females displaying higher levels than males, even under identical hormonal conditions as adults. These findings, in conjunction with accumulating evidence implicating kisspeptins as potent secretagogues of gonadotropin-releasing hormone (GnRH), suggest that the sex-specific display of the LH surge (positive feedback) reflects sexual differentiation of AVPV Kiss1 neurons. In addition, developmental kisspeptin signaling via its receptor GPR54 appears to be critical in males for the proper sexual differentiation of a variety of sexually dimorphic traits, ranging from complex social behavior to specific forebrain and spinal cord neuronal populations. This review discusses the recent data, and their implications, regarding the bi-directional relationship between the Kiss1 system and the process of sexual differentiation.
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Affiliation(s)
- Alexander S Kauffman
- Department of Physiology & Biophysics, Health Sciences Building, Box 357290, University of Washington, Seattle, WA 98195, United States.
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18
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Popa SM, Clifton DK, Steiner RA. The role of kisspeptins and GPR54 in the neuroendocrine regulation of reproduction. Annu Rev Physiol 2008; 70:213-38. [PMID: 17988212 DOI: 10.1146/annurev.physiol.70.113006.100540] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Neurons that produce gonadotropin-releasing hormone (GnRH) reside in the basal forebrain and drive reproductive function in mammals. Understanding the circuitry that regulates GnRH neurons is fundamental to comprehending the neuroendocrine control of puberty and reproduction in the adult. This review focuses on a family of neuropeptides encoded by the Kiss1 gene, the kisspeptins, and their cognate receptor, GPR54, which have been implicated in the regulation of GnRH secretion. Kisspeptins are potent secretagogues for GnRH, and the Kiss1 gene is a target for regulation by gonadal steroids (e.g., estradiol and testosterone), metabolic factors (e.g., leptin), photoperiod, and season. Kiss1 neurons in the arcuate nucleus may regulate the negative feedback effect of gonadal steroids on GnRH and gonadotropin secretion in both sexes. The expression of Kiss1 in the anteroventral periventricular nucleus (AVPV) is sexually dimorphic, and Kiss1 neurons in the AVPV may participate in the generation of the preovulatory GnRH/luteinizing hormone (LH) surge in the female rodent. Kiss1 neurons have emerged as primary transducers of internal and environmental cues to regulate the neuroendocrine reproductive axis.
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Affiliation(s)
- Simina M Popa
- Graduate Program in Molecular and Cellular Biology, University of Washington, Seattle, WA 98195-6460, USA
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19
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Campbell RE, Herbison AE. Definition of brainstem afferents to gonadotropin-releasing hormone neurons in the mouse using conditional viral tract tracing. Endocrinology 2007; 148:5884-90. [PMID: 17823269 PMCID: PMC6101187 DOI: 10.1210/en.2007-0854] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Brainstem monoamines have long been considered to play a role in regulating the activity of GnRH neurons, although their neuroanatomical relationship with these cells has remained unclear. Using a Cre-dependent pseudorabies virus (Ba2001) technique that permits retrograde tracing selectively from GnRH neurons in the mouse, we have examined the organization of brainstem inputs to rostral preoptic area (rPOA) GnRH neurons. Two days after injection of Ba2001 into the rPOA of adult female GnRH-Cre transgenic mice, five to nine GnRH neurons located immediately adjacent to the injection site were found to express green fluorescent protein (GFP), the marker of virus infection, with no GFP expression anywhere else in the brain. In mice killed 24 h later (3 d after injection), GFP-expressing cells were identified (in order of density) in the raphe nuclei, periaqueductal grey, locus coeruleus, nucleus tractus solitarius, and area postrema. This time course is compatible with these neurons representing primary afferent inputs to the GnRH neurons. Four and 6 d after Ba2001 injection, GFP-expressing cells were found in additional brain regions. Dual-label immunofluorescence experiments in 3-d postinjection mice demonstrated that 100% of GFP-expressing neurons in the raphe were positive for tryptophan hydroxylase, whereas 100% and approximately 50% of GFP neurons in the locus coeruleus and nucleus tractus solitarius, respectively, expressed tyrosine hydroxylase. These observations demonstrate that rPOA GnRH neurons receive direct projections from brainstem A2 and A6 noradrenergic neurons and that, surprisingly, the largest afferent input from the brainstem originates from raphe serotonin neurons in the mouse.
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Affiliation(s)
- Rebecca E Campbell
- Centre for Neuroendocrinology, Department of Physiology, University of Otago School of Medical Sciences, Dunedin, New Zealand 9001
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20
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Kauffman AS, Clifton DK, Steiner RA. Emerging ideas about kisspeptin- GPR54 signaling in the neuroendocrine regulation of reproduction. Trends Neurosci 2007; 30:504-11. [PMID: 17904653 DOI: 10.1016/j.tins.2007.08.001] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 07/31/2007] [Accepted: 08/01/2007] [Indexed: 11/17/2022]
Abstract
Neurons that produce gonadotropin-releasing hormone (GnRH) drive the reproductive axis, but the molecular and cellular mechanisms by which hormonal and environmental signals regulate GnRH secretion remain poorly understood. Kisspeptins are products of the Kiss1 gene, and the interaction of kisspeptin and its receptor GPR54 plays a crucial role in governing the onset of puberty and adult reproductive function. This review discusses the latest ideas about kisspeptin-GPR54 signaling in the neuroendocrine regulation of reproduction, with special emphasis on the role of Kiss1 and kisspeptin in the negative and positive feedback control of gonadotropin secretion by sex steroids, timing of puberty onset, sexual differentiation of the brain and photoperiodic regulation of seasonal reproduction.
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21
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Ben Saïd S, Lomet D, Chesneau D, Lardic L, Canepa S, Guillaume D, Briant C, Fabre-Nys C, Caraty A. Differential Estradiol Requirement for the Induction of Estrus Behavior and the Luteinizing Hormone Surge in Two Breeds of Sheep1. Biol Reprod 2007; 76:673-80. [PMID: 17202388 DOI: 10.1095/biolreprod.106.057406] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
For a better understanding of the mechanisms that lead to the preovulatory GnRH/LH surge and estrus behavior, the minimum estradiol (E) requirements (dose and duration) to induce each of these events were determined and compared between two breeds of ewes having either single (Ile de France) or multiple (Romanov) ovulations. The ewes were initially studied during a natural estrus cycle, and were then ovariectomized and run through successive artificial estrus cycles. For these artificial cycles the duration and amplitude of the follucular phase E increase were manipulated by E implants. Under all conditions, the onset of estrus behavior was similar in the two breeds, although its duration was longer in Romanov ewes. While a moderate E signal (6 cm for 12 h) induced an LH surge in 10/10 Ile de France ewes, a larger E signal (12 cm for 12 h) was minimally effective in Romanov ewes (4/10). Additional studies revealed that a small E signal (3 cm for 6 h) induced full estrus behavior in all Romanov ewes but was completely ineffective in Ile de France animals (0/10). Higher doses and mostly longer durations of the E signal (12 cm for 24 h) were required to induce a surge in all the Romanov ewes. These results demonstrate a clear difference in the E requirement for the induction of estrus behavior and the LH surge between breeds of ewes that have different ovulation rates. These data provide compelling evidence that, in one breed, the neuronal systems that regulate both events require different estrogen signals.
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Affiliation(s)
- S Ben Saïd
- UMR Physiologie de la Reproduction et des Comportements, INRA/CNRS/Université Tours/Haras Nationaux, 37380 Nouzilly, France
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22
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Yasuo S, Nakao N, Ohkura S, Iigo M, Hagiwara S, Goto A, Ando H, Yamamura T, Watanabe M, Watanabe T, Oda SI, Maeda KI, Lincoln GA, Okamura H, Ebihara S, Yoshimura T. Long-day suppressed expression of type 2 deiodinase gene in the mediobasal hypothalamus of the Saanen goat, a short-day breeder: implication for seasonal window of thyroid hormone action on reproductive neuroendocrine axis. Endocrinology 2006; 147:432-40. [PMID: 16195409 DOI: 10.1210/en.2005-0507] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In most animals that live in temperate regions, reproduction is under photoperiodic control. In long-day breeders such as Japanese quail and Djungarian hamsters, type 2 deiodinase (Dio2) plays an important role in the mediobasal hypothalamus, catalyzing the conversion of prohormone T4 to bioactive T3 to regulate the photoperiodic response of the gonads. However, the molecular basis for seasonal reproduction in short-day breeders remains unclear. Because thyroid hormones are also known to be involved in short-day breeders, we examined the effect of an artificial long-day stimulus on Dio2 expression in the male Saanen goat (Capra hircus), a short-day breeder. Dio2 expression was observed in the caudal continuation of the arcuate nucleus, known as the target site for both melatonin and T4 action. In addition, expression of Dio2 and T3 content in the mediobasal hypothalamus was suppressed by artificial long-day conditions, which is the opposite of the results of long-day breeders. Thyroid hormone action on the development of neuroendocrine anestrus is known to be limited to a specific seasonal window. This long-day suppression of Dio2 may provide a mechanism that accounts for the lack of responsiveness to thyroxine during the mid to late anestrus.
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Affiliation(s)
- Shinobu Yasuo
- Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan
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23
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Pompolo S, Ischenko O, Pereira A, Iqbal J, Clarke IJ. Evidence that projections from the bed nucleus of the stria terminalis and from the lateral and medial regions of the preoptic area provide input to gonadotropin releasing hormone (GNRH) neurons in the female sheep brain. Neuroscience 2005; 132:421-36. [PMID: 15802194 DOI: 10.1016/j.neuroscience.2004.12.042] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2004] [Indexed: 11/18/2022]
Abstract
The arcuate nucleus/ventromedial hypothalamic nucleus (ARC/VMH) region is thought to relay estrogen feedback signals to gonadotropin-releasing hormone (GnRH) cells in the sheep brain. This region sends major projections to the lateral preoptic area (lPOA), ventral bed nucleus of the stria terminals (vBnST) and the ventro-caudal division of the median preoptic nucleus (vcMePON) with little direct input to GnRH cell bodies, suggesting interneuronal relay to GnRH neurons. The brain stem also provides input to the POA. The present study aimed to identify possible relay circuits in the POA and BnST to GnRH neurons. Biotinylated dextran amine (BDA) was injected into lPOA (n=6), vBnST (n=2), vcMePON (n=3) and periventricular nucleus (PeriV; n=1) of ewes for anterograde tracing. GnRH immunoreactive (IR) perikarya appearing to receive input from BDA-containing varicosities were identified by fluorescence microscopy, with further analysis by confocal microscopy. When BDA was injected into rostral and caudal regions of lPOA (n=3), no tracer-filled varicose fibers were found in contact with GnRH-IR perikarya. Injections into the center of the lPOA (n=3) indicated direct projections to GnRH-IR cells. Injections into the vBnST, vcMePON and PeriV indicated that cells of these regions also provide input to GnRH cells. BDA-containing varicosities found in the MPOA were immunoreactive for NPY or were GABAergic or glutamatergic when the tracer was injected into vBnST and lPOA, but not when injections were placed in the vcMePON. With injection into the PeriV, tracer-filled varicosities in the MPOA were not immunoreactive for somatostatin or enkephalin. Injection of FluoroGold into ventral POA retrogradely labeled cells in the above mentioned areas, but few were also immunoreactive for estrogen receptor-alpha. Thus, cells of the vBnST, lPOA, vcMePON and PeriV project to GnRH neurons. These cells may provide an interneuronal route to GnRH neurons from the ARC/VMH, the brain stem and other regions of the brain.
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Affiliation(s)
- S Pompolo
- Prince Henry's Institute of Medical Research, PO Box 5152, Clayton, Victoria 3168, Australia.
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24
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Tourlet S, Ziyazetdinova G, Caraty A, Tramu G, Delsol G, Tillet Y. Oestradiol effect on galanin-immunoreactive neurones in the diencephalon of the ewe. J Neuroendocrinol 2005; 17:145-51. [PMID: 15796766 DOI: 10.1111/j.1365-2826.2005.01291.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Galanin is a neuropeptide involved in the regulation of numerous functions such as reproduction. In female rats, this peptide stimulates gonadotropin-releasing hormone (GnRH)/luteinizing hormone release and its synthesis is stimulated by oestradiol. It could therefore be an intermediary between the oestrogenic signal from the ovaries and the GnRH neurones (e.g. during the time course leading to the preovulatory GnRH surge). However, although the involvement of galanin is well-known in rodents, it is poorly understood in ewes. Using immunohistochemistry with a specific antigalanin antiserum, we detected the peptide in neurones of two groups of ovariectomized ewes treated for 6 h with subcutaneous implants, either with oestradiol (experimental group) or empty (control group). The galanin-immunoreactive neurones were counted in three areas, the preoptic area, the bed nucleus of the stria terminalis and the infundibular nucleus, using a computerized image analysis system. There was no change in the mean number of galanin-immunoreactive (GAL-ir) neurones in the infundibular nucleus (37 +/- 12 neurones/section in treated animals and 31 +/- 11 in controls) or in the bed nucleus of the stria terminalis (22 +/- 5 neurones/section in treated animals and 16 +/- 4 in controls), but the number of GAL-ir neurones was higher in the preoptic area in treated than in control ewes (35 +/- 4 versus 14 +/- 10, P < 0.001). To determine whether the neurones of the preoptic area were directly sensitive to oestradiol, we performed double immunohistochemical labelling for oestradiol receptor alpha and galanin. More than 50% of the GAL-ir neurones contained the oestradiol receptor alpha and therefore could be directly regulated by oestradiol. These results indicate that oestradiol might act directly on a GAL-ir neuronal population situated in the preoptic area, without any effect on the GAL-ir neurones of the infundibular nucleus or the bed nucleus of the stria terminalis. Because a 6-h oestradiol treatment can induce a preovulatory GnRH surge in ewes, the GAL-ir neuronal population of the preoptic area might be one of the neuronal systems by which oestradiol activates the GnRH neurones. However, although the morphological relationships between galanin and GnRH neurones have been described in rodents, they remain to be demonstrated in the ewe.
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Affiliation(s)
- S Tourlet
- INRA-PRC, CNRS, Université de Tours, Haras Nationaux, Nouzilly, France
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25
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Richter TA, Robinson JE, Lozano JM, Evans NP. Progesterone can block the preovulatory gonadotropin-releasing hormone/luteinising hormone surge in the ewe by a direct inhibitory action on oestradiol-responsive cells within the hypothalamus. J Neuroendocrinol 2005; 17:161-9. [PMID: 15796768 DOI: 10.1111/j.1365-2826.2005.01287.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Elevated oestradiol concentrations during the follicular phase stimulate a surge in gonadotropin-releasing hormone (GnRH) and luteinising hormone (LH) concentrations, which leads to ovulation. Progesterone can block the oestradiol-induced GnRH/LH surge, but the mechanism that is involved is unclear. We examined the effect of progesterone on oestradiol-induced activation of cells within the ovine hypothalamus/preoptic area (POA) to determine: (i) in which regions progesterone acts to block the GnRH/LH surge and (ii) whether progesterone directly or indirectly prevents activation of oestradiol-responsive cells. Cellular activation was assessed by measuring the number of cells that expressed Fos (an immediate early gene). Exposure to increased oestradiol concentrations in the absence of progesterone (which normally stimulates a LH surge) did not cause any region-specific changes in hypothalamic Fos expression during the activation stage of the LH surge-induction process (Experiment 1). The same treatment significantly increased cellular activation within the POA, lateral septum (LS), and arcuate nucleus at the time of surge onset (Experiment 2). Concurrent exposure to increased oestradiol and progesterone concentrations during the activation stage of the surge-induction process (which normally blocks the LH surge) was associated with significantly reduced cellular activation within the ventromedial hypothalamus and anterior hypothalamic area, relative to the positive controls (oestradiol increment alone) and arcuate nucleus relative to the negative controls (no increment in oestradiol) during the activation stage (Experiment 1). At the time of surge onset (Experiment 2), exposure to progesterone during the activation period prevented the oestradiol-induced increase in cellular activation that occurred in the POA, LS and arcuate nucleus of the positive controls. These results demonstrated that oestradiol and progesterone induced differential region- and time-specific effects on cellular activation within the regions of the ovine brain that generate the preovulatory GnRH/LH surge. Moreover, the lack of cellular activation within the POA, LS and arcuate nucleus at the time of surge onset in animals exposed to progesterone during the activation stage is consistent with the hypothesis that progesterone can block the preovulatory surge by direct inhibition of oestradiol-induced cellular activation in these areas.
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Affiliation(s)
- T A Richter
- Laboratory of Neuroendocrinology, The Babraham Institute, Cambridge, UK
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26
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Abstract
Although the mechanisms underlying hypothalamic surge secretion of gonadotropin-releasing hormone (GnRH) in rodent models have remained enduring mysteries in the field of neuroendocrinology, the identities of two fundamental constituents are clear. Elevated ovarian oestrogen, in conjunction with circadian signals, combine to elicit GnRH surges that are confined to the afternoon of the proestrus phase. The phenomenon of oestrogen positive feedback, although extensively investigated, is not completely understood, and may involve the actions of this steroid directly on GnRH perikarya, as well as on the activity of neuronal afferents. Additionally, whereas many studies have focused upon regulation of GnRH surge secretion by the neuroanatomical biological clock, the suprachiasmatic nucleus, it remains unclear why this daily signal is capable of stimulating surges only in the presence of oestrogen. This review re-examines multiple models of circadian control of reproductive neurosecretion, armed with the recent characterisation of the intracellular transcriptional feedback loops that comprise the circadian clock, and attempts to evaluate previous studies on this topic within the context of these new discoveries. Recent advances reveal the presence of oscillating circadian clocks throughout the central nervous system and periphery, including the anterior pituitary and hypothalamus, raising the possibility that synchrony between multiple cellular clocks may be involved in GnRH surge generation. Current studies are reviewed that demonstrate the necessity of functional clock oscillations in generating GnRH pulsatile secretion in vitro, suggesting that a GnRH-specific intracellular circadian clock may underlie GnRH surges as well. Multiple possible steroidal and neuronal contributions to GnRH surge generation are discussed, in addition to how these signals of disparate origin may be integrated at the cellular level to initiate this crucial reproductive event.
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Affiliation(s)
- P E Chappell
- Department of Reproductive Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0674, USA.
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27
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Dufourny L, Caraty A, Clarke IJ, Robinson JE, Skinner DC. Progesterone-receptive beta-endorphin and dynorphin B neurons in the arcuate nucleus project to regions of high gonadotropin-releasing hormone neuron density in the ovine preoptic area. Neuroendocrinology 2005; 81:139-49. [PMID: 15976512 DOI: 10.1159/000086527] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Accepted: 04/05/2005] [Indexed: 11/19/2022]
Abstract
Progesterone inhibits gonadotropin-releasing hormone (GnRH) secretion through interneuronal systems located in the mediobasal hypothalamus in ewes. Endogenous opioid peptides are implicated in this inhibition of GnRH secretion. The distributions of endogenous opioid peptides are known to overlap with progesterone receptors (PR) in the arcuate nucleus. We investigated whether PR is expressed by beta-endorphin and dynorphin B neurons in the arcuate nucleus and if a subset of double-labeled cells projects to the preoptic area where most GnRH neurons are detected. Injection of a retrograde tracer, Fluorogold, into the rostral preoptic area was performed in ovariectomized ewes pretreated with estrogen and progesterone. Brain sections were processed using double immunocytochemistry. Only brains of ewes with an injection site encompassing at least 80 GnRH neurons were processed for PR and then either beta-endorphin or dynorphin B immunocytochemistry. Antigen retrieval is essential for PR detection but causes Fluorogold to fade. Thus, quantitative analysis was performed on photographs taken before and after antigen retrieval. We found that 25-30% of PR-containing neurons, 20% of beta-endorphin cells and 22% of dynorphin B neurons in the arcuate nucleus project toward the preoptic area. From the PR/beta-endorphin double-labeled cells that represent 25 and 36% of PR and beta-endorphin cells, respectively, 35% were labeled with Fluorogold. From the PR/dynorphin B double-labeled cells that account for 39 and 62% of PR and dynorphin B neurons, respectively, 26% contained Fluorogold. These data strongly support the hypothesis that progesterone acts in the arcuate nucleus through beta-endorphin and dynorphin B neurons to affect preoptic area GnRH neurons.
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Affiliation(s)
- Laurence Dufourny
- Department of Zoology & Physiology, University of Wyoming, Laramie, WY 82071, USA
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Dufourny L, Caraty A, Clarke IJ, Robinson JE, Skinner DC. Progesterone-receptive dopaminergic and neuropeptide Y neurons project from the arcuate nucleus to gonadotropin-releasing hormone-rich regions of the ovine preoptic area. Neuroendocrinology 2005; 82:21-31. [PMID: 16330883 DOI: 10.1159/000090122] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 09/29/2005] [Indexed: 11/19/2022]
Abstract
Progesterone inhibits gonadotropin-releasing hormone (GnRH) secretion in sheep through an interneuronal system located in the mediobasal hypothalamus. This study focused on known inhibitors of GnRH secretion in sheep, dopamine and neuropeptide Y (NPY). As the distributions of tyrosine hydroxylase (TH)- and NPY-immunoreactive neurons overlap with progesterone receptors (PR) in the arcuate nucleus, we hypothesized that, if these neurons mediate, at least partially, the inhibitory feedback signal of progesterone, then they should co-express PRs. Fluorogold (FG), a retrograde tracer, was injected into the preoptic area of ovariectomized ewes pretreated with estrogen and progesterone. When the FG injection site encompassed at least 80 GnRH neurons, sections from the arcuate nucleus were processed using dual immunocytochemistry for PR and either TH or NPY. We found that 30% of PR-immunoreactive, 12% of TH-containing and 21% of NPY-synthesizing neurons project toward this GnRH-rich region. Of the PR/TH dual-labeled cells, which represent 21% of PR and 31% of TH cells, respectively, 22% displayed FG labeling. Of the PR/NPY neurons, which account for 19% of PR and 67% of NPY neurons, respectively, 26% were FG fluorescent. This study suggests that subsets of arcuate nucleus dopaminergic and NPY neurons may transduce, at least in part, the progesterone-mediated inhibition of GnRH secretion.
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Affiliation(s)
- Laurence Dufourny
- Department of Zoology & Physiology, University of Wyoming, Laramie, WY 82071, USA
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Pillon D, Caraty A, Fabre-Nys C, Lomet D, Cateau M, Bruneau G. Regulation by estradiol of hypothalamic somatostatin gene expression: possible involvement of somatostatin in the control of luteinizing hormone secretion in the ewe. Biol Reprod 2004; 71:38-44. [PMID: 14985243 DOI: 10.1095/biolreprod.103.023689] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In the ewe, the mediobasal hypothalamus (MBH) is the primary central site for estradiol to generate the preovulatory GnRH/LH surges and sexual behavior. This area contains numerous neurons expressing the estradiol receptor alpha, distributed in the ventromedial nucleus (VMN) and the infundibular nucleus (IN). A large proportion of these neurons express somatostatin, making this neuropeptide a potential candidate for transmission of the estradiol signal to the GnRH neurons located in the preoptic area. We tested this hypothesis using ovariectomized ewes that had been subjected to an artificial estrous cycle. In the first experiment, 22 h after progesterone removal, ewes received estradiol (treated ewes) or empty implants (control ewes) for 4 h and then were killed. Using in situ hybridization, we showed that this short estradiol treatment increased the somatostatin mRNA amount by about 50% in the VMN and 42% in the IN. In the second experiment, preovulatory estradiol signal was replaced by somatostatin intracerebroventricular (ICV) administration. This treatment abolished LH pulsatility and dramatically decreased the mean basal level of LH secretion while it did not affect the mean plasma GH concentration. We demonstrated that an increase in somatostatin mRNA occurs at the time of the negative feedback effect of estradiol on LH secretion during the early stage of the GnRH surge induction. As ICV somatostatin administration inhibits the pulsatile LH secretion by acting on the central nervous system, we suggest that somatostatin synthesized in the MBH could be involved in the estradiol negative feedback before the onset of the preovulatory surge.
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Affiliation(s)
- Delphine Pillon
- Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique/Centre National de la Recherche Scientifique/Universite Francois Rabelais de Tours, 37380 Nouzilly, France
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Romanowicz K, Misztal T, Barcikowski B. Genistein, a phytoestrogen, effectively modulates luteinizing hormone and prolactin secretion in ovariectomized ewes during seasonal anestrus. Neuroendocrinology 2004; 79:73-81. [PMID: 15004429 DOI: 10.1159/000076630] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2003] [Accepted: 12/30/2003] [Indexed: 11/19/2022]
Abstract
Through binding with estrogen receptors, phytoestrogens, plant-derived estrogen-like compounds, affect numerous reproductive functions. It is not known whether these compounds are capable of evoking effective changes in luteinizing hormone (LH) and prolactin (PRL) secretion in ewes by acting directly within the central nervous system (CNS). The hypothesis studied was that genistein, infused for several hours into the third ventricle, could immediately affect LH and PRL secretion in ovariectomized (OVX) ewes during seasonal anestrus. Two doses of genistein, 1 microg/100 microl/h (total 4 microg, n = 7) and 10 microg/100 microl/h (total 40 microg, n = 7), were infused intracerebroventricularly from 12.00 to 16.00 h and blood samples were collected from 8.00 to 20.00 h at 10-min intervals. Randomly selected ewes were infused with a vehicle (control, n = 5). The mean plasma LH concentration in control ewes was significantly (p < 0.01) higher during infusion of the vehicle than before the infusion. It remained on an insignificantly changed level after the infusion. The frequency of LH pulses in control ewes did not differ significantly before, during, or after vehicle infusion. In ewes infused with a lower dose of genistein, plasma LH concentrations decreased significantly (p < 0.001) after the infusion, as compared with the values noted before and during genistein infusion. Only a tendency towards a decrease in LH pulse frequency occurred after infusion of a lower dose of genistein. In ewes infused with a higher dose of genistein, the plasma LH concentration decreased significantly (p < 0.01) after phytoestrogen administration as compared with the values noted before and during infusion. The frequency of LH pulses was also significantly (p < 0.01) lower after genistein administration. Because the changes in PRL secretion were more dynamic in response to genistein infusion, the statistical analysis included 2-hour periods. The mean plasma PRL concentration in control animals was significantly enhanced (p < 0.01) only during the first 2-hour period of sampling. After that it decreased and remained on an unchanged level up to the end of sampling. Similar changes in PRL secretion were observed in both experimental groups before genistein infusion. In contrast, significant (p < 0.01 to p < 0.001) increases in PRL concentration were noted regularly during and shortly after the genistein infusion in either low-dose or high-dose genistein-infused ewes, compared with the concentrations noted before genistein treatment. Plasma PRL concentrations during and after genistein infusion in both experimental groups were also significantly higher than the control (p < 0.01 to p < 0.001). The presented data demonstrate that genistein, a phytoestrogen, may effectively modulate LH and PRL secretion in OVX ewes by acting within the CNS.
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Affiliation(s)
- Katarzyna Romanowicz
- Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Jabłonna n/Warsaw, Poland
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Tsai PS, Lunden JB, Jones JT. Effects of steroid hormones on spermatogenesis and GnRH release in male Leopard frogs, Rana pipiens. Gen Comp Endocrinol 2003; 134:330-8. [PMID: 14636640 DOI: 10.1016/j.ygcen.2003.07.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Several lines of evidence suggest reproduction in the ranid frogs is potently regulated by the gonadal steroids, in particular 5alpha-dihydrotestosterone (DHT) and 17beta-estradiol (E(2)), and a non-gonadal steroid, the stress hormone corticosterone (Cort). Little is known about how these steroid hormones act upon the GnRH system to regulate the downstream reproductive events. We address these gaps in our knowledge by investigating the effects of Cort, E(2), and DHT administration on the in vitro release of GnRH and on the spermatogenesis of adult male leopard frog, Rana pipiens. R. pipiens were implanted for 20 days with silastic capsules containing cholesterol (Ch; control), Cort, E(2), or DHT. Upon sacrifice, acute hypothalamic explants were cultured and measured for GnRH release, and testes processed for histological analysis. Although only E(2) implant significantly reduced the gonadosomatic index, all three steroid hormones altered spermatogenesis. Cort modestly but significantly reduced the presence of spermatids. The effects of E(2) and DHT were both stimulatory and inhibitory, depending on the stage of spermatogenesis. None of the steroid hormones altered baseline GnRH release. Interestingly, only E(2) significantly stimulated veratridine-induced GnRH release, suggesting E(2) treatment increased the releasable pool of GnRH and/or enhance the excitability of GnRH neurons. In sum, this is the first study to report the direct measurement of GnRH secretion in a poikilothermic tetrapod. Our results revealed potent but sometimes paradoxical effects of steroid hormones, especially E(2), on the reproductive regulation of the male R. pipiens.
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Affiliation(s)
- Pei San Tsai
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA.
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Pompolo S, Pereira A, Kaneko T, Clarke IJ. Seasonal changes in the inputs to gonadotropin-releasing hormone neurones in the ewe brain: an assessment by conventional fluorescence and confocal microscopy. J Neuroendocrinol 2003; 15:538-45. [PMID: 12694380 DOI: 10.1046/j.1365-2826.2003.01030.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The seasonal pattern of breeding in sheep offers an opportunity to examine plasticity of neuronal inputs to gonadotropin-releasing hormone (GnRH) neurones. We used conventional fluorescence microscopy and confocal microscopy to compare the extent of input to GnRH neurones from various neuropeptide/neurotransmitter systems in ewes during the breeding and anestrous seasons. Using double-labelling immunohistochemistry, we counted close appositions between GnRH cells and varicosities that were immunoreactive for either glutamic acid decarboxylase (GAD; for gamma-amino butyric acid-GABA-neurones), dopamine beta hydroxylase (DBH; for noradrenergic neurones), vesicular glutamate transporter-1 (VGluT-1, for glutamatergic neurones), neuropeptide Y (NPY) and tyrosine hydroxylase (TH; for dopaminergic/noradrenergic neurones). The percentage of GnRH cells displaying close appositions to GABA-ergic varicosities was higher (P < 0.02) in anestrus than in the breeding season. The percentage of GnRH cells receiving input from varicosities that were positive for TH, DBH and VGluT-1 was similar in both seasons. Approximately 26-49% of GnRH neurones were seen to receive inputs from NPY, TH, GABAergic or noradrenergic neurones, while a larger number of GnRH cells (72-75%) received input from glutamatergic neurones. Conventional microscopy consistently overestimated the number of close contacts on GnRH neurones compared to confocal microscopy. For TH-immunoreactive varicosities in the preoptic area, only 16-35% were also immunoreactive for DBH, suggesting that the remainder are dopaminergic. Approximately half of the noradrenergic inputs in the preoptic area were also immunoreactive for NPY. In conclusion, we present numerical data on the consensus between light and confocal microscopy and the level of input of various neuronal systems to GnRH cells; the data indicate a seasonal change in the GABAergic input to GnRH neurones.
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Affiliation(s)
- S Pompolo
- Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia.
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Scott CJ, Clarke IJ, Tilbrook AJ. Neuronal inputs from the hypothalamus and brain stem to the medial preoptic area of the ram: neurochemical correlates and comparison to the ewe. Biol Reprod 2003; 68:1119-33. [PMID: 12606458 DOI: 10.1095/biolreprod.102.010595] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The retrograde tracer, FluoroGold, was used to trace the neuronal inputs from the septum, hypothalamus, and brain stem to the region of the GnRH neurons in the rostral preoptic area of the ram and to compare these imputs with those in the ewe. Sex differences were found in the number of retrogradely labeled cells in the dorsomedial and ventromedial nuclei. Retrogradely labeled cells were also observed in the lateral septum, preoptic area, organum vasculosum of the lamina terminalis, bed nucleus of the stria terminalis, stria terminalis, subfornical organ, periventricular nucleus, anterior hypothalamic area, lateral hypothalamus, arcuate nucleus, and posterior hypothalamus. These sex differences may partially explain sex differences in how GnRH secretion is regulated. Fluorescence immunohistochemistry was used to determine the neurochemical identity of some of these cells in the ram. Very few tyrosine hydroxylase-containing neurons in the A14 group (<1%), ACTH-containing neurons (<1%), and neuropeptide Y-containing neurons (1-5%) in the arcuate nucleus contained FluoroGold. The ventrolateral medulla and parabrachial nucleus contained the main populations of FluoroGold-containing neurons in the brain stem. Retrogradely labeled neurons were also observed in the nucleus of the solitary tract, dorsal raphe nucleus, and periaqueductal gray matter. Virtually all FluoroGold-containing cells in the ventrolateral medulla and about half of these cells in the nucleus of the solitary tract also stained for dopamine beta-hydroxylase. No other retrogradely labeled cells in the brain stem were noradrenergic. Although dopamine, beta-endorphin, and neuropeptide Y have been implicated in the regulation of GnRH secretion in males, it is unlikely that these neurotransmitters regulate GnRH secretion via direct inputs to GnRH neurons.
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Dufourny L, Skinner DC. Influence of estradiol on NADPH diaphorase/neuronal nitric oxide synthase activity and colocalization with progesterone or type II glucocorticoid receptors in ovine hypothalamus. Biol Reprod 2002; 67:829-36. [PMID: 12193391 DOI: 10.1095/biolreprod.102.004648] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Nitric oxide (NO) has been shown to play an important role in both the neuroendocrine reproductive and stress axes, which are closely linked. Because progesterone (P4) receptors (PRs) and glucocorticoid receptors (GRs) are not found in GnRH neurons and the NOergic system has been implicated in the control of GnRH secretion, this study aimed to ascertain whether steroids altered the NOergic system. Our first objective was to map the distribution of NO synthase (NOS) cells in the ovine preoptic area (POA) and hypothalamus and to determine whether NOS activity is enhanced by estradiol (E2) treatment. Using NADPH diaphorase (NADPHd) histochemistry, we found that NADPHd-positive neurons were spread throughout the ovine POA and hypothalamus, and that all NADPHd cells were immunoreactive for NOS. In response to estradiol, a significant increase in the number of NADPHd cells was noted only in the ventrolateral region of the ventromedial nucleus (VMNvl), with no significant difference in the POA or arcuate nucleus. Progesterone and glucocorticoid receptors were colocalized with NADPHd reactive neurons in the POA, arcuate nucleus, and VMNvl of ewes in both treatment groups. In ewes receiving estradiol, the number of NADPHd-positive cells containing steroid receptors in the POA (PR, 81%; GR, 79%) and arcuate nucleus (PR, 89%; GR, 84%) was similar, but in the VMNvl, fewer NADPHd-positive cells contained GR (PR, 88%, GR, 31%). These data show that estradiol up-regulates NOS activity in a site-specific manner and that the influence and possible interaction of progesterone and corticosteroids on NO producing cells may differ according to the neural location.
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Affiliation(s)
- Laurence Dufourny
- Department of Clinical Veterinary Science, University of Bristol, Langford BS40 5DU, United Kingdom.
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Goubillon ML, Caraty A, Herbison AE. Evidence in favour of a direct input from the ventromedial nucleus to gonadotropin-releasing hormone neurones in the ewe: an anterograde tracing study. J Neuroendocrinol 2002; 14:95-100. [PMID: 11849368 DOI: 10.1046/j.0007-1331.2001.00739.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mechanism by which oestrogen activates the gonadotropin releasing hormone (GnRH) neurones to induce the preovulatory luteinizing hormone (LH) surge is not understood. Previous work in the ewe has suggested that the primary site of action for oestradiol in stimulating the GnRH neurones was in the region of the ventromedial nucleus (VMN) within the mediobasal hypothalamus (MBH). In the present study, we used anterograde tracing techniques in the ewe to investigate whether direct neuronal projections may exist from neurones located in the region of the VMN to the GnRH neurones. Following the injection of biotinylated dextran amine into the VMN of four ewes, anterogradely labelled fibres were found located principally within the ipsilateral diagonal band of Broca (DBB), septum, preoptic and anterior hypothalamic areas, and periventricular, paraventricular, dorsomedial and arcuate nuclei of the MBH. Dual-labelling for GnRH revealed that fibres containing anterograde tracer were adjacent to the soma and/or dendrites of approximately 50% of all ipsilateral GnRH neurones located throughout the DBB and hypothalamus. Few anterogradely labelled fibres were detected within the median eminence. Although such studies cannot define the presence of direct synaptic connections between VMN neurones and the GnRH cells, these observations support further the hypothesis that oestrogen-sensitive VMN neurones represent a direct transsynaptic input to the GnRH cell bodies which are involved in the generation of the LH surge in the ewe.
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Affiliation(s)
- M-L Goubillon
- Laboratory of Neuroendocrinology, The Babraham Institute, Cambridge, UK
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36
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Clarke IJ, Pompolo S, Scott CJ, Rawson JA, Caddy D, Jakubowska AE, Pereira AM. Cells of the arcuate nucleus and ventromedial nucleus of the ovariectomized ewe that respond to oestrogen: a study using Fos immunohistochemistry. J Neuroendocrinol 2001; 13:934-41. [PMID: 11737551 DOI: 10.1046/j.1365-2826.2001.00694.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Oestrogen produces a positive feedback effect on the secretion of gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) when implanted into the ventromedial/arcuate nucleus of the ovariectomized (OVX) ewe. This has led to the belief that it is in this area of the hypothalamus that oestrogen causes the preovulatory surge in GnRH/LH. To date, however, the cell types that are integral to this response have not been identified. The present study aimed to examine cellular responsiveness to oestrogen in this region of the brain using Fos immunohistochemistry and further aimed to determine the cell type that shows an acute response to oestrogen. OVX ewes (n = 4-6 per group) were given i.m. injections of oestradiol benzoate or oil (vehicle) and were killed 1-6 h later. Brains were perfused for immunohistochemistry. The number of cells in the arcuate nucleus which were immunopositive for Fos was greater (two- to fourfold) in the oestradiol benzoate-treated OVX ewes (n = 5) 1 h after injection. The number of Fos-positive cells in the ventromedial hypothalamic nucleus was 10-fold greater in the oestradiol benzoate-treated ewes 1 h after injection. Because there were high levels of Fos-immunoreactive cells in oil-treated ewes, we repeated the experiment with i.v. injection of 50 microg oestrogen or vehicle (n = 5). With this latter procedure, we found that oestrogen injection caused a significant increase in the number of Fos immunoreactive cells in the arcuate nucleus within 1 h, but there was no response in the ventromedial hypothalamus. To further characterize the types of cells that might respond to oestrogen, we double-labelled cells for Fos and either adrenocorticotropin hormone, neuropeptide Y or tyrosine hydroxylase (a marker for dopaminergic cells). These cell types could account for less than 30% of the total number of cells that were Fos-positive and oestrogen treatment did not cause an increase in the Fos labelling of any of these types of cell. These data show that oestrogen activates cells of the arcuate/ventromedial hypothalamus within 1 h of injection and that this response could relate to the feedback effects of this gonadal hormone. The majority of cells that produce Fos following oestrogen injection are of unknown phenotype. The data further suggest that induction of cells of the ventromedial hypothalamic nucleus require more prolonged oestrogen stimulus than cells of the arcuate nucleus.
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Affiliation(s)
- I J Clarke
- Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia. iain.clarke.@med.monash.edu.au
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Pompolo S, Rawson JA, Clarke IJ. Projections from the arcuate/ventromedial region of the hypothalamus to the preoptic area and bed nucleus of stria terminalis in the brain of the ewe; lack of direct input to gonadotropin-releasing hormone neurons. Brain Res 2001; 904:1-12. [PMID: 11516406 DOI: 10.1016/s0006-8993(01)02372-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This study aimed to determine whether cells in the region of the arcuate and ventromedial hypothalamic nuclei (ARC/VMH) project to the gonadotropin-releasing hormone (GnRH) cells in the preoptic area (POA) and diagonal band of Broca (dbB) of the female sheep brain. An anterograde tracer, biotinylated dextran amine (BDA), was injected (70 nl) into the ARC/VMH (n=7) and the brains were perfused 3 weeks later. BDA terminals were mainly found in the dbB, POA and bed nucleus of stria terminalis (BNST). In order to determine the extent of input to GnRH neurons, we performed immunocytochemistry on the same sections with a GnRH antibody and examined close association of GnRH-immunoreactive (GnRH-IR) neurons (cell bodies and proximal dendrites) with BDA terminals. Of 223 GnRH-IR neurons that were examined, only three (1.3%) had BDA terminals in close proximity. Neither was close proximity observed between BDA terminals and GnRH-IR fibres. Injection of BDA into the BNST (n=6) showed terminals in POA, but only one of 273 GnRH-IR cells examined had BDA terminals in close proximity and no GnRH-IR fibres had BDA terminals in close proximity. Our results suggest that (1) although there are projections from the VMH/ARC to the dbB, POA and BNST, an interneuron or chain of interneurons is required for input to the GnRH neurones; (2) any input to GnRH neurons from the BNST involves at least one interneuron. The identity of these interneurons remains to be determined. Thus, input to the GnRH neurons from the estrogen receptor-rich area of ARC/VMH and from the BNST is not direct.
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Affiliation(s)
- S Pompolo
- Prince Henry's Institute of Medical Research, P.O. Box 5152, 3168, Victoria, Clayton, Australia.
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Deitch HR, Mershon JL, Clark KE. Estrogen receptor beta is the predominant isoform expressed in the brain of adult and fetal sheep. Am J Obstet Gynecol 2001; 184:1077-9. [PMID: 11349162 DOI: 10.1067/mob.2001.115223] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The objective of this study was to examine the expression of estrogen receptors alpha and beta in the cerebral cortex of the adult and fetal sheep. STUDY DESIGN A reverse transcriptase-polymerase chain reaction-based approach was used to examine the expression of ovine estrogen receptor alpha and estrogen receptor beta in the cerebral cortex of 4 adult and 2 fetal sheep. RESULTS Estrogen receptor beta was expressed in the 4 adult and 2 fetal brain samples. Estrogen receptor alpha expression was seen in only 1 adult brain and 1 fetal brain. CONCLUSION Estrogen receptor beta is the predominant isoform expressed in the cerebral cortex of both adult and fetal sheep. These data may have implications for the many important actions of estrogen in the adult and developing ovine brain.
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Affiliation(s)
- H R Deitch
- Department of Obstetrics and Gynecology, College of Medicine, University of Cincinnati, Ohio 45267-0526, USA
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Walsh JP, Rao A, Thompson RC, Clarke IJ. Proenkephalin and opioid mu-receptor mRNA expression in ovine hypothalamus across the estrous cycle. Neuroendocrinology 2001; 73:26-36. [PMID: 11174014 DOI: 10.1159/000054617] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The neural mechanism underlying the preovulatory surge of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) is thought to include reduced opioid inhibition of GnRH secretion (disinhibition). Possible mechanisms for disinhibition include reduced endogenous opioid peptide or receptor mRNA expression. Proenkephalin and opioid mu-receptor mRNA expression were measured by in situ hybridization using 35S-labeled cRNA probes and computer-assisted grain counting in hypothalamic nuclei of ovary-intact ewes (n = 4) killed on day 10 of the luteal phase or 24 or 48 h into the follicular phase. In a second experiment, proenkephalin and mu-receptor mRNA expression were compared in ewes killed on day 10 of the luteal phase or during the preovulatory LH surge. Cells expressing proenkephalin mRNA were more widely distributed in ovine hypothalamus than previously described. In the periventricular nucleus, there was a significant reduction in the grain count per cell and the number of labeled cells during the follicular phase and during the LH surge, as compared to the luteal phase. In the ventromedial hypothalamus, there was a significant reduction in the grain count per cell during the follicular phase and LH surge as compared to the luteal phase, but no change in the number of labeled cells. No differences in proenkephalin mRNA expression were detected in the medial septum, diagonal band of Broca, preoptic area, anterior hypothalamic area or paraventricular nucleus across the estrous cycle. Cells expressing opioid mu-receptor mRNA were also widely distributed. No difference in mu-receptor mRNA expression was detected in the medial septum, diagonal band, medial preoptic area, anterior hypothalamus or bed nucleus of the stria terminalis across the cycle. We conclude that in sheep, proenkephalin gene expression in the periventricular nucleus and ventromedial hypothalamus is reduced during the follicular phase and at the time of the LH surge. This may be part of the neural mechanism underlying the GnRH/LH surge in this species.
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Affiliation(s)
- J P Walsh
- Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia
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Goubillon ML, Forsdike RA, Robinson JE, Ciofi P, Caraty A, Herbison AE. Identification of neurokinin B-expressing neurons as an highly estrogen-receptive, sexually dimorphic cell group in the ovine arcuate nucleus. Endocrinology 2000; 141:4218-25. [PMID: 11089556 DOI: 10.1210/endo.141.11.7743] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Studies were undertaken to examine the hypothesis that neurons expressing neurokinin B (NKB) may represent an estrogen-receptive input to GnRH neurons in the sheep. Cells immunoreactive for NKB were located almost exclusively within the arcuate nucleus of the ovine hypothalamus. Dual labeling experiments revealed that essentially all NKB neurons (97%) were immunoreactive for estrogen receptor alpha and that NKB-immunoreactive fibers were found in close proximity to approximately 40% of GnRH neurons located in the rostral preoptic area as well as intermingled with GnRH fibers in the median eminence. The analysis of male and female brains revealed a marked female-dominant sex difference in the numbers of NKB neurons, and sections obtained from in utero androgen-treated females indicated that this sex difference resulted from an organizational influence of testosterone during neural development. In adult ovariectomized ewes, in situ hybridization studies failed to detect any significant effect of 8- to 26-h exposure of estrogen on cellular NKB messenger RNA levels. Together, these studies identify the first sexually differentiated neuronal cell population in the ovine hypothalamus and, remarkably, show that essentially all of these female-dominant NKB neurons express estrogen receptors. Although these neurons may be involved in any number of steroid-dependent, sexually differentiated functions in the sheep, the neuroanatomical evidence for potential NKB inputs to GnRH neurons suggests a role for this novel population in the regulation of reproductive function.
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Affiliation(s)
- M L Goubillon
- Laboratory of Neuroendocrinology, The Babraham Institute, Cambridge, United Kingdom
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Scott CJ, Tilbrook AJ, Rawson JA, Clarke IJ. Gonadal steroid receptors in the regulation of GnRH secretion in farm animals. Anim Reprod Sci 2000; 60-61:313-26. [PMID: 10844203 DOI: 10.1016/s0378-4320(00)00103-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The sites of action and mechanisms by which gonadal steroids regulate gonadotrophin-releasing hormone (GnRH) in domestic animals remain largely unknown. This review summarises information gained from sheep regarding the distribution of the gonadal steroid receptors in the brain, the neurochemical identity and the projections of these steroid receptor-containing neurones. The cells in the hypothalamus that contain each of the gonadal steroid receptors (oestrogen receptor alpha (ERalpha), oestrogen receptor beta (ERbeta), progesterone receptor (PR) and androgen receptor (AR)) show a remarkably similar distribution, although the PR and AR-containing cells are less widespread than oestrogen receptors (ERs). There is considerable overlap in the distribution of ERalpha- and ERbeta-containing cells but also some unique sites for each subtype. This suggests differential regulation of the actions of oestrogen. There appears to be little sexual dimorphism in the distribution of the gonadal steroid receptors in the hypothalamus, with the notable exception of the ventromedial nucleus where females appear to have greater numbers of both ERalpha- and ERbeta-containing cells. Neuronal tracing studies have identified projections of some of the ERalpha-containing cells to sites that may allow interaction with the GnRH system. The receptor mapping, neuronal tracing and microimplantation studies suggest that the ventromedial nucleus is likely to be a key hypothalamic nucleus in the steroid regulation of GnRH secretion in sheep.
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Affiliation(s)
- C J Scott
- Department of Physiology, Monash University, Vic 3168, Clayton, Australia.
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