1
|
Farkas I, Skrapits K, Sárvári M, Göcz B, Takács S, Rumpler É, Hrabovszky E. Functional GnRH receptor signaling regulates striatal cholinergic neurons in neonatal but not in adult mice. Front Endocrinol (Lausanne) 2024; 15:1353151. [PMID: 38348415 PMCID: PMC10859511 DOI: 10.3389/fendo.2024.1353151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Accepted: 01/12/2024] [Indexed: 02/15/2024] Open
Abstract
Reproduction in mammals is controlled by hypothalamic gonadotropin-releasing hormone (GnRH) neurons. Recent studies from our laboratory established that the basal ganglia of the human brain contain additional large populations of GnRH synthesizing neurons which are absent in adult mice. Such extrahypothalamic GnRH neurons mostly occur in the putamen where they correspond to subsets of the striatal cholinergic interneurons (ChINs) and express GnRHR autoreceptors. In an effort to establish a mouse model for functional studies of striatal GnRH/GnRHR signaling, we carried out electrophysiological experiments on acute brain slices from male transgenic mice. Using PN4-7 neonatal mice, half of striatal ChINs responded with transient hyperpolarization and decreased firing rate to 1.2 µM GnRH, whereas medium spiny projection neurons remained unaffected. GnRH acted on its specific receptor because no response was observed in the presence of the GnRHR antagonist Antide. Addition of the membrane-impermeable G protein-coupled receptor inhibitor GDP-β-S to the internal electrode solution eliminated the effect of GnRH. Further, GnRH was able to inhibit ChINs in presence of tetrodotoxin which blocked action potential mediated events. Collectively, these data indicated that the receptor underlying the effects of GnRH in neonatal mice is localized within ChINs. GnRH responsiveness of ChINs was transient and entirely disappeared in adult mice. These results raise the possibility to use neonatal transgenic mice as a functional model to investigate the role of GnRH/GnRHR signaling discovered earlier in adult human ChINs.
Collapse
Affiliation(s)
- Imre Farkas
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine (Hungarian Research Network), Budapest, Hungary
| | | | | | | | | | | | - Erik Hrabovszky
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine (Hungarian Research Network), Budapest, Hungary
| |
Collapse
|
2
|
Campbell RE, Coolen LM, Hoffman GE, Hrabovszky E. Highlights of neuroanatomical discoveries of the mammalian gonadotropin-releasing hormone system. J Neuroendocrinol 2022; 34:e13115. [PMID: 35502534 PMCID: PMC9232911 DOI: 10.1111/jne.13115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 02/09/2022] [Accepted: 03/01/2022] [Indexed: 11/17/2022]
Abstract
The anatomy and morphology of gonadotropin-releasing hormone (GnRH) neurons makes them both a joy and a challenge to investigate. They are a highly unique population of neurons given their developmental migration into the brain from the olfactory placode, their relatively small number, their largely scattered distribution within the rostral forebrain, and, in some species, their highly varied individual anatomical characteristics. These unique features have posed technological hurdles to overcome and promoted fertile ground for the establishment and use of creative approaches. Historical and more contemporary discoveries defining GnRH neuron anatomy remain critical in shaping and challenging our views of GnRH neuron function in the regulation of reproductive function. We begin this review with a historical overview of anatomical discoveries and developing methodologies that have shaped our understanding of the reproductive axis. We then highlight significant discoveries across specific groups of mammalian species to address some of the important comparative aspects of GnRH neuroanatomy. Lastly, we touch on unresolved questions and opportunities for future neuroanatomical research on this fascinating and important population of neurons.
Collapse
Affiliation(s)
- Rebecca E. Campbell
- Centre for Neuroendocrinology and Department of Physiology, School of Biomedical SciencesUniversity of OtagoDunedinNew Zealand
| | - Lique M. Coolen
- Department of Biological SciencesKent State UniversityKentOhioUSA
| | | | - Erik Hrabovszky
- Laboratory of Reproductive NeurobiologyInstitute of Experimental MedicineBudapestHungary
| |
Collapse
|
3
|
Skrapits K, Sárvári M, Farkas I, Göcz B, Takács S, Rumpler É, Váczi V, Vastagh C, Rácz G, Matolcsy A, Solymosi N, Póliska S, Tóth B, Erdélyi F, Szabó G, Culler MD, Allet C, Cotellessa L, Prévot V, Giacobini P, Hrabovszky E. The cryptic gonadotropin-releasing hormone neuronal system of human basal ganglia. eLife 2021; 10:67714. [PMID: 34128468 PMCID: PMC8245125 DOI: 10.7554/elife.67714] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 06/14/2021] [Indexed: 01/20/2023] Open
Abstract
Human reproduction is controlled by ~2000 hypothalamic gonadotropin-releasing hormone (GnRH) neurons. Here, we report the discovery and characterization of additional ~150,000–200,000 GnRH-synthesizing cells in the human basal ganglia and basal forebrain. Nearly all extrahypothalamic GnRH neurons expressed the cholinergic marker enzyme choline acetyltransferase. Similarly, hypothalamic GnRH neurons were also cholinergic both in embryonic and adult human brains. Whole-transcriptome analysis of cholinergic interneurons and medium spiny projection neurons laser-microdissected from the human putamen showed selective expression of GNRH1 and GNRHR1 autoreceptors in the cholinergic cell population and uncovered the detailed transcriptome profile and molecular connectome of these two cell types. Higher-order non-reproductive functions regulated by GnRH under physiological conditions in the human basal ganglia and basal forebrain require clarification. The role and changes of GnRH/GnRHR1 signaling in neurodegenerative disorders affecting cholinergic neurocircuitries, including Parkinson’s and Alzheimer’s diseases, need to be explored.
Collapse
Affiliation(s)
- Katalin Skrapits
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Miklós Sárvári
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Imre Farkas
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Balázs Göcz
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Szabolcs Takács
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Éva Rumpler
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Viktória Váczi
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Csaba Vastagh
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Gergely Rácz
- 1st Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary
| | - András Matolcsy
- 1st Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary
| | - Norbert Solymosi
- Centre for Bioinformatics, University of Veterinary Medicine, Budapest, Hungary
| | - Szilárd Póliska
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Blanka Tóth
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Budapest, Hungary
| | - Ferenc Erdélyi
- Department of Gene Technology and Developmental Biology, Institute of Experimental Medicine, Budapest, Hungary
| | - Gábor Szabó
- Department of Gene Technology and Developmental Biology, Institute of Experimental Medicine, Budapest, Hungary
| | | | - Cecile Allet
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, Lille, France
| | - Ludovica Cotellessa
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, Lille, France
| | - Vincent Prévot
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, Lille, France
| | - Paolo Giacobini
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, Lille, France
| | - Erik Hrabovszky
- Laboratory of Reproductive Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| |
Collapse
|
4
|
Progesterone-induced amplification and advancement of GnRH/LH surges are associated with changes in kisspeptin system in preoptic area of estradiol-primed female rats. Brain Res 2016; 1650:21-30. [DOI: 10.1016/j.brainres.2016.08.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 08/15/2016] [Accepted: 08/16/2016] [Indexed: 11/20/2022]
|
5
|
Eghlidi DH, Urbanski HF. Effects of Age and Estradiol on Gene Expression in the Rhesus Macaque Hypothalamus. Neuroendocrinology 2015; 101:236-45. [PMID: 25765287 PMCID: PMC4475460 DOI: 10.1159/000381063] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 02/18/2015] [Indexed: 11/19/2022]
Abstract
BACKGROUND The hypothalamus plays a key role in mediating the effects of estrogen on many physiological functions, including reproduction, metabolism, and thermoregulation. We have previously observed marked estrogen-dependent gene expression changes within the hypothalamus of rhesus macaques during aging, especially in the KNDy neurons of the arcuate-median eminence (ARC-ME) that produce kisspeptin, neurokinin B, and dynorphin A. Little is known, however, about the mechanisms involved in mediating the feedback from estrogen onto these neurons. METHODS We used quantitative real-time PCR to profile age- and estrogen-dependent gene expression changes in the rhesus macaque hypothalamus. Our focus was on genes that encode steroid receptors (ESR1, ESR2, PGR, and AR) and on enzymes that contribute to the local synthesis of 17β-estradiol (E2; STS, HSD3B1/2, HSD17B5, and CYP19A). In addition, we used RT(2) Profiler™ PCR Arrays to profile a larger set of genes that are integral to hypothalamic function. RESULTS KISS1, KISS1R, TAC3, and NPY2R mRNA levels increased in surgically menopausal (ovariectomized) old females relative to age-matched ovariectomized animals that received E2 hormone therapy. In contrast, PGR, HSD17B, GNRH2, SLC6A3, KISS1, TAC3, and NPY2R mRNA levels increased after E2 supplementation. CONCLUSION The rhesus macaque ARC-ME expresses many genes that are responsive to changes in circulating estrogen levels, even during old age, and these may contribute to causing the normal and pathophysiological changes that occur during menopause.
Collapse
Affiliation(s)
- Dominique H. Eghlidi
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, Oreg., USA
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, Oreg., USA
| | - Henryk F. Urbanski
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, Oreg., USA
- Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, Oreg., USA
- Deptartment of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oreg., USA
| |
Collapse
|
6
|
Urbanski HF. Differential roles of GnRH-I and GnRH-ii neurons in the control of the primate reproductive axis. Front Endocrinol (Lausanne) 2012; 3:20. [PMID: 22645518 PMCID: PMC3355843 DOI: 10.3389/fendo.2012.00020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Accepted: 01/23/2012] [Indexed: 11/21/2022] Open
Abstract
In vertebrates, gonadotropin-releasing hormone (GnRH) represents the primary neuroendocrine link between the brain and the reproductive axis, and in some species up to three different forms of GnRH have been detected. Until recently, it had been assumed that humans and non-human primates only express one form (GnRH-I), but it is now clear they also express a second form (GnRH-II). GnRH-II, like GnRH-I, is highly effective at stimulating gonadotropin release, both in vitro and in vivo, but the neurons that produce GnRH-II are completely distinct from those producing GnRH-I. Moreover, GnRH-II and GnRH-I producing neurons respond very differently to estradiol; specifically, estradiol stimulates GnRH-II gene expression in the former and inhibit GnRH-I gene expression in the latter. Consequently, the negative feedback action of estradiol may be mediated exclusively by the subpopulation of GnRH neurons that express GnRH-I, while the positive feedback action may be mediated exclusively by the subpopulation that expresses GnRH-II. Taken together, these findings raise the possibility that two completely different GnRH neuronal systems participate in the control of primate reproductive physiology. The primary role of GnRH-I neurons is likely to be focused on the maintenance and modulation of tonic pulsatile LH release, whereas the primary role of GnRH-II neurons is likely to be focused on the generation of the preovulatory LH surge. This functional segregation of the primate neuroendocrine reproductive axis lends itself for novel targeted approaches to fertility control and for treatment of human reproductive disorders.
Collapse
Affiliation(s)
- Henry F. Urbanski
- Division of Neuroscience, Oregon National Primate Research CenterBeaverton, OR, USA
- Division of Reproductive and Developmental Sciences, Oregon National Primate Research CenterBeaverton, OR, USA
- Department of Behavioral Neuroscience, Oregon Health and Science UniversityPortland, OR, USA
- Department of Physiology and Pharmacology, Oregon Health and Science UniversityPortland, OR, USA
- *Correspondence: Henry F. Urbanski, Division of Neuroscience, Oregon National Primate Research Center, 505 Northwest 185th Avenue, Beaverton, OR 97006, USA. e-mail:
| |
Collapse
|
7
|
Kim W, Jessen HM, Auger AP, Terasawa E. Postmenopausal increase in KiSS-1, GPR54, and luteinizing hormone releasing hormone (LHRH-1) mRNA in the basal hypothalamus of female rhesus monkeys. Peptides 2009; 30:103-10. [PMID: 18619506 PMCID: PMC2612733 DOI: 10.1016/j.peptides.2008.06.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 06/10/2008] [Accepted: 06/12/2008] [Indexed: 10/21/2022]
Abstract
The G-protein coupled receptor, GPR54, and its ligand, kisspeptin-54 (a KiSS-1 derived peptide) have been reported to be important players in control of LHRH-1 release. However, the role of the GPR54 signaling in primate reproductive senescence is still unclear. In the present study we investigated whether KiSS-1, GPR54, and LHRH-1 mRNA in the brain change after menopause in female rhesus monkeys using quantitative real-time PCR. Results indicate that KiSS-1, GPR54, and LHRH-1 mRNA levels in the medial basal hypothalamus (MBH) in postmenopausal females (28.3+/-1.1 years of age, n=5) were all significantly higher than that in eugonadal adult females (14.7+/-2.1 years of age, n=9), whereas KiSS-1, GPR54, and LHRH-1 mRNA levels in the preoptic area (POA) did not have any significant changes between the two age groups. To further determine the potential contribution by the absence of ovarian steroids, we compared the changes in KiSS-1, GPR54, and LHRH-1 mRNA levels in young adult ovarian intact vs. young ovariectomized females. Results indicate that KiSS-1 and LHRH-1 mRNA levels in the MBH, not POA, in ovariectomized females were significantly higher than those in ovarian intact females, whereas GPR54 mRNA levels in ovariectomized females had a tendency to be elevated in the MBH, although the values were not quite statistically significant. Collectively, in the primate the reduction in the negative feedback control by ovarian steroids appears to be responsible for the aging changes in kisspeptin-GPR54 signaling and the elevated state of the LHRH-1 neuronal system.
Collapse
Affiliation(s)
- Wooram Kim
- Wisconsin National Primate Research Center, University of Wisconsin, 1223 Capitol Court, Madison, WI 53715-1299, USA
| | | | | | | |
Collapse
|
8
|
Rance NE. Menopause and the human hypothalamus: evidence for the role of kisspeptin/neurokinin B neurons in the regulation of estrogen negative feedback. Peptides 2009; 30:111-22. [PMID: 18614256 PMCID: PMC2632595 DOI: 10.1016/j.peptides.2008.05.016] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [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: 05/01/2008] [Accepted: 05/05/2008] [Indexed: 10/22/2022]
Abstract
Menopause is characterized by depletion of ovarian follicles, a reduction of ovarian hormones to castrate levels and elevated levels of serum gonadotropins. Rather than degenerating, the reproductive neuroendocrine axis in postmenopausal women is intact and responds robustly to the removal of ovarian hormones. Studies in both human and non-human primates provide evidence that the gonadotropin hypersecretion in postmenopausal women is secondary to increased gonadotropin-releasing hormone (GnRH) secretion from the hypothalamus. In addition, menopause is accompanied by hypertrophy of neurons in the infundibular (arcuate) nucleus expressing KiSS-1, neurokinin B (NKB), substance P, dynorphin and estrogen receptor alpha (ERalpha) mRNA. Ovariectomy in experimental animals induces nearly identical findings, providing evidence that these changes are a compensatory response to ovarian failure. The anatomical site of the hypertrophied neurons, as well as the extensive data implicating kisspeptin, NKB and dynorphin in the regulation of GnRH secretion, provide compelling evidence that these neurons are part of the neural network responsible for the increased levels of serum gonadotropins in postmenopausal women. We propose that neurons expressing KiSS-1, NKB, substance P, dynorphin and ERalpha mRNA in the infundibular nucleus play an important role in sex-steroid feedback on gonadotropin secretion in the human.
Collapse
Affiliation(s)
- Naomi E Rance
- Departments of Pathology, Cell Biology and Anatomy and Neurology and the Evelyn F. McKnight Brain Institute, University of Arizona College of Medicine, 1501 N. Campbell Avenue, Tucson, AZ 85724, USA.
| |
Collapse
|
9
|
Bethea CL, Centeno ML, Cameron JL. Neurobiology of stress-induced reproductive dysfunction in female macaques. Mol Neurobiol 2008; 38:199-230. [PMID: 18931961 PMCID: PMC3266127 DOI: 10.1007/s12035-008-8042-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Accepted: 09/15/2008] [Indexed: 11/24/2022]
Abstract
It is now well accepted that stress can precipitate mental and physical illness. However, it is becoming clear that given the same stress, some individuals are very vulnerable and will succumb to illness while others are more resilient and cope effectively, rather than becoming ill. This difference between individuals is called stress sensitivity. Stress sensitivity of an individual appears to be influenced by genetically inherited factors, early life (even prenatal) stress, and by the presence or absence of factors that provide protection from stress. In comparison to other stress-related diseases, the concept of sensitivity versus resilience to stress-induced reproductive dysfunction has received relatively little attention. The studies presented herein were undertaken to begin to identify stable characteristics and the neural underpinnings of individuals with sensitivity to stress-induced reproductive dysfunction. Female cynomolgus macaques with normal menstrual cycles either stop ovulating (stress sensitive) or to continue to ovulate (stress resilient) upon exposure to a combined metabolic and psychosocial stress. However, even in the absence of stress, the stress-sensitive animals have lower secretion of the ovarian steroids, estrogen and progesterone, have higher heart rates, have lower serotonin function, have fewer serotonin neurons and lower expression of pivotal serotonin-related genes, have lower expression of 5HT2A and 2C genes in the hypothalamus, have higher gene expression of GAD67 and CRH in the hypothalamus, and have reduced gonadotropin-releasing hormone transport to the anterior pituitary. Altogether, the results suggest that the neurobiology of reproductive circuits in stress-sensitive individuals is compromised. We speculate that with the application of stress, the dysfunction of these neural systems becomes exacerbated and reproductive function ceases.
Collapse
Affiliation(s)
- Cynthia L Bethea
- Division of Reproductive Sciences, Oregon National Primate Research Center, Beaverton, OR 97006, USA.
| | | | | |
Collapse
|
10
|
Centeno ML, Sanchez RL, Cameron JL, Bethea CL. Hypothalamic gonadotrophin-releasing hormone expression in female monkeys with different sensitivity to stress. J Neuroendocrinol 2007; 19:594-604. [PMID: 17620101 DOI: 10.1111/j.1365-2826.2007.01566.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Psychosocial stress, combined with mild dieting and moderate exercise, are observed in women seeking treatment for hypothalamic amenorrhea. Using female cynomolgus macaques, we previously reported that the same combination of mild stresses suppressed reproductive hormone secretion and menstrual cycles in some individuals (stress-sensitive, SS), but not in others (highly stress-resilient, HSR). Compared to HSR monkeys, SS monkeys exhibited lower oestradiol and progesterone levels at the midcycle peak and decreased gene expression in the central serotonergic system during nonstressed cycles. Because steroids and serotonin impinge upon the hypothalamic-pituitary-gonadal (HPG) axis, we hypothesised that the differences between SS and HSR monkeys in the sensitivity of the HPG axis to stress may ultimately manifest in differences in the gonadotrophin-releasing hormone (GnRH) system. GnRH in situ hybridisation and immunohistochemistry were performed with hypothalamic sections from SS and HSR animals, euthanised in the early follicular phase of a nonstressed menstrual cycle. Compared to HSR monkeys, SS monkeys exhibited a significantly higher number and density of GnRH cell bodies, as well as a higher number of soma with extremely robust expression of GnRH mRNA, but SS monkeys exhibited a lower density of immunostained GnRH fibres in the median eminence. We suggest that neuronal mechanisms involved in the control of GnRH synthesis, transport and release differ in SS compared to HSR animals.
Collapse
Affiliation(s)
- M-L Centeno
- Division of Reproductive Sciences, Oregon National Primate Research Centre, Beaverton, OR 97006, USA.
| | | | | | | |
Collapse
|
11
|
Jahan S, Jalali S, Shami SA. Neuroendocrine regulation of prolactin secretion in adult female rhesus monkeys during different phases of the menstrual cycle: role of neuroexcitatory amino acid (NMA). Am J Primatol 2007; 69:395-406. [PMID: 17154384 DOI: 10.1002/ajp.20357] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The present study attempts to examine the role of N-methyl-D, L-aspartate (NMDA) receptors in the central regulation of prolactin (PRL) secretion, which may be involved in ovarian function and its alteration by glutamate in various phases of the menstrual cycle of female rhesus monkeys (Macaca mulatta). The results suggest that the glutaminergic component of the control system, which governs PRL secretion by utilizing NMDA receptors, may have an important role in regulating changes in PRL secretion. The response of PRL during the luteal phase of the cycle was different from that observed in follicular and menstrual phases. Steroids may influence the NMDA-dependent drive to release PRL. N-methyl-D-aspartic acid (NMA) involvement in the regulation of PRL secretion may occur through activation of the PRL-stimulating system depending on the physiological state or steroidal milieu. It is possible, therefore, that the NMA-induced release of PRL-releasing factors (PRF) and PRL are enhanced in the presence of ovarian feedback.
Collapse
Affiliation(s)
- S Jahan
- Department of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
| | | | | |
Collapse
|
12
|
Abstract
Comprehensive studies have provided a clear understanding of the effects of gonadal steroids on the secretion of gonadotropin releasing hormone (GnRH), but some inconsistent results exist with regard to effects on synthesis. It is clear that regulation of both synthesis and the secretion of GnRH are effected by neurotransmitter systems in the brain. Thus, steroid regulation of GnRH synthesis and secretion can be direct, but the predominant effects are transmitted through steroid-responsive neuronal systems in various parts of the brain. There is also emerging evidence of direct effects on GnRH cells. Overriding effects on synthesis and secretion of GnRH can be observed during aging, in undernutrition and under stressful situations; these involve various neuronal systems, which may have serial or parallel effects on GnRH cells. The effect of aging is accompanied by changes in GnRH synthesis, but comprehensive studies of synthesis during undernutrition and stress are less well documented. Altered GnRH and gonadotropin secretion that occurs in seasonal breeding animals and during the pubertal transition is not generally accompanied by changes in GnRH synthesis. Secretion of GnRH from the brain is a reflection of the inherent function of GnRH cells and the inputs that integrate all of the central regulatory elements. Ultimately, the pattern of secretion dictates the reproductive status of the organism. In order to fully understand the central mechanisms that control reproduction, more extensive studies are required on the neuronal circuitry that provides input to GnRH cells.
Collapse
Affiliation(s)
- Iain J Clarke
- Prince Henry's Institute of Medical Research, P.O. Box 5152, Clayton 3168, Australia.
| | | |
Collapse
|
13
|
Abizaid A, Horvath B, Keefe DL, Leranth C, Horvath TL. Direct visual and circadian pathways target neuroendocrine cells in primates. Eur J Neurosci 2004; 20:2767-76. [PMID: 15548220 DOI: 10.1111/j.1460-9568.2004.03737.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The effect of light on neuroendocrine functions is thought to be mediated through retinal inputs to the circadian pacemaker, the hypothalamic suprachiasmatic nucleus (SCN). The present studies were conducted to provide experimental evidence for this signaling modality in non-human primates. In the St. Kitts vervet monkey, anterograde tracing of SCN efferents revealed a monosynaptic pathway between the circadian clock and hypothalamic neurons producing luteinizing hormone-releasing hormone (LHRH). Using a variety of tracing techniques, direct retinal input was found to be abundant in the SCN and in other hypothalamic sites. Strikingly, in hypothalamic areas other than the SCN, primary visual afferents established direct contacts with neuroendocrine cells including those producing LHRH and dopamine, neurons that are the hypothalamic regulators of pituitary gonadotrops and prolactin. Thus, our data reveal for the first time in primates that light stimuli can reach the hypothalamo-pituitary-gonadal axis, directly providing a pathway independent of but parallel to that of the circadian clock for the photic modulation of hormone release.
Collapse
Affiliation(s)
- Alfonso Abizaid
- Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, CT 06510, USA
| | | | | | | | | |
Collapse
|
14
|
Gore AC, Windsor-Engnell BM, Terasawa E. Menopausal increases in pulsatile gonadotropin-releasing hormone release in a nonhuman primate (Macaca mulatta). Endocrinology 2004; 145:4653-9. [PMID: 15231708 DOI: 10.1210/en.2004-0379] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Reproductive function in all vertebrates is controlled by the circhoral release of the neuropeptide, GnRH, into the portal capillary system leading to the anterior pituitary. Despite its primary role in sexual maturation and the maintenance of adult reproductive function, changes in the concentrations and pattern of GnRH release have not yet been reported in any primate species during the menopausal transition and postmenopause. Such knowledge is essential for ascertaining both the mechanisms for, and consequences of, the menopausal process. Here we used a push-pull perfusion method to measure and compare the parameters of pulsatile GnRH release in adult rhesus monkeys at 8.4 +/- 1.5 yr (young adult females, early follicular phase, n = 6) and 28.8 +/- 0.3 yr (aged females, n = 4, of which two monkeys were in the menopausal transition, and two were postmenopausal). Our results demonstrate that: 1) GnRH release is pulsatile in both young and aged monkeys; 2) mean concentrations of GnRH increase during reproductive aging; and 3) GnRH pulse frequency does not differ between aged monkeys and young monkeys in the early follicular phase. We conclude that not only do GnRH neurons have the continued capacity to release GnRH in a pulsatile manner but also they can do so with enhanced GnRH levels in aged primates. To our knowledge, this is the first direct demonstration of elevated pulsatile GnRH concentrations in a primate species during reproductive senescence, a result that may have implications for menopausal symptoms.
Collapse
Affiliation(s)
- Andrea C Gore
- University of Texas at Austin, Division of Pharmacology/Toxicology, Austin, Texas 78712, USA.
| | | | | |
Collapse
|
15
|
Petersen SL, Ottem EN, Carpenter CD. Direct and indirect regulation of gonadotropin-releasing hormone neurons by estradiol. Biol Reprod 2003; 69:1771-8. [PMID: 12890720 DOI: 10.1095/biolreprod.103.019745] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Estrogen signaling to GnRH neurons is critical for coordinating the preovulatory surge release of LH with follicular maturation. Until recently it was thought that estrogen signaled GnRH neurons only indirectly through numerous afferent systems. This minireview presents new evidence indicating that GnRH neurons are directly regulated by estradiol (E2), primarily through estrogen receptor (ER)-beta, and indirectly through E2-sensitive neurons in the anteroventral periventricular (AVPV) region. The data described suggest that E2 generally represses GnRH gene expression but that this repression is transiently overcome by indirect E2-dependent signals relayed by AVPV neurons. We also present evidence that the AVPV neurons responsible for relaying E2 signals to GnRH neurons are multifunctional gamma aminobutyric acid-ergic/glutamatergic/neuropeptidergic neurons.
Collapse
Affiliation(s)
- Sandra L Petersen
- Department of Biology, Neuroscience and Behavior Graduate Program, Center for Neuroendocrine Studies, University of Massachusetts, Amherst, Massachusetts 01003, USA.
| | | | | |
Collapse
|