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Moenter SM, Starrett JR. Estradiol action in the female hypothalamo-pituitary-gonadal axis. J Neuroendocrinol 2024:e13390. [PMID: 38606585 DOI: 10.1111/jne.13390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 03/06/2024] [Accepted: 03/27/2024] [Indexed: 04/13/2024]
Abstract
It has now been about a century since a flurry of discoveries identified first the pituitary, then more specifically the anterior pituitary and soon thereafter the central nervous system as components regulating gonadal and downstream reproductive functions. This was an era of ablation/replacement designs using at first rudimentary and then increasingly pure preparations of gonadal and pituitary "activities" or transplanting actual glands, whole or homogenized, among subjects. There was, of course, controversy as is typical of lively and productive scientific debates to this day. The goals of this commentary are to briefly review the history of this work and how the terms referring to interactions among the components of the hypothalamo (as the central neural component was soon associated with)-pituitary-gonadal (HPG) axis evolved, and then to question if the current terms used have kept up with our understanding of the system. The focus in this review will be the actions of estradiol primarily upon the hypothalamus. Important actions of progesterone on the hypothalamus as well as both steroids on the pituitary response to hypothalamic factors are both acknowledged and largely ignored in this document, as are any sex differences as we focus on females.
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Affiliation(s)
- Suzanne M Moenter
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
- Department of Obstetrics & Gynecology, University of Michigan, Ann Arbor, Michigan, USA
- The Reproductive Sciences Program, University of Michigan, Ann Arbor, Michigan, USA
| | - J Rudolph Starrett
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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McQuillan HJ, Clarkson J, Kauff A, Han SY, Yip SH, Cheong I, Porteous R, Heather AK, Herbison AE. Definition of the estrogen negative feedback pathway controlling the GnRH pulse generator in female mice. Nat Commun 2022; 13:7433. [PMID: 36460649 PMCID: PMC9718805 DOI: 10.1038/s41467-022-35243-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 11/23/2022] [Indexed: 12/03/2022] Open
Abstract
The mechanisms underlying the homeostatic estrogen negative feedback pathway central to mammalian fertility have remained unresolved. Direct measurement of gonadotropin-releasing hormone (GnRH) pulse generator activity in freely behaving mice with GCaMP photometry demonstrated striking estradiol-dependent plasticity in the frequency, duration, amplitude, and profile of pulse generator synchronization events. Mice with Cre-dependent deletion of ESR1 from all kisspeptin neurons exhibited pulse generator activity identical to that of ovariectomized wild-type mice. An in vivo CRISPR-Cas9 approach was used to knockdown ESR1 expression selectively in arcuate nucleus (ARN) kisspeptin neurons. Mice with >80% deletion of ESR1 in ARN kisspeptin neurons exhibited the ovariectomized pattern of GnRH pulse generator activity and high frequency LH pulses but with very low amplitude due to reduced responsiveness of the pituitary. Together, these studies demonstrate that estrogen utilizes ESR1 in ARN kisspeptin neurons to achieve estrogen negative feedback of the GnRH pulse generator in mice.
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Affiliation(s)
- H James McQuillan
- Centre for Neuroendocrinology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand.,Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand
| | - Jenny Clarkson
- Centre for Neuroendocrinology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand.,Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand
| | - Alexia Kauff
- Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand
| | - Su Young Han
- Centre for Neuroendocrinology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand.,Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand.,Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, CB2 3EG, UK
| | - Siew Hoong Yip
- Centre for Neuroendocrinology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand.,Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand
| | - Isaiah Cheong
- Centre for Neuroendocrinology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand.,Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand
| | - Robert Porteous
- Centre for Neuroendocrinology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand.,Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand
| | - Alison K Heather
- Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand
| | - Allan E Herbison
- Centre for Neuroendocrinology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand. .,Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, 9054, New Zealand. .,Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, CB2 3EG, UK.
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Moenter SM, Silveira MA, Wang L, Adams C. Central aspects of systemic oestradiol negative- and positive-feedback on the reproductive neuroendocrine system. J Neuroendocrinol 2020; 32:e12724. [PMID: 31054210 PMCID: PMC6829026 DOI: 10.1111/jne.12724] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 04/24/2019] [Accepted: 04/26/2019] [Indexed: 12/24/2022]
Abstract
The central nervous system regulates fertility via the release of gonadotrophin-releasing hormone (GnRH). This control revolves around the hypothalamic-pituitary-gonadal axis, which operates under traditional homeostatic feedback by sex steroids from the gonads in males and most of the time in females. An exception is the late follicular phase in females, when homeostatic feedback is suspended and a positive-feedback response to oestradiol initiates the preovulatory surges of GnRH and luteinising hormone. Here, we briefly review the history of how mechanisms underlying central control of ovulation by circulating steroids have been studied, discuss the relative merit of different model systems and integrate some of the more recent findings in this area into an overall picture of how this phenomenon occurs.
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Affiliation(s)
- Suzanne M. Moenter
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, 48109
- Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, 48109
| | - Marina A. Silveira
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109
| | - Luhong Wang
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109
| | - Caroline Adams
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109
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McQuillan HJ, Han SY, Cheong I, Herbison AE. GnRH Pulse Generator Activity Across the Estrous Cycle of Female Mice. Endocrinology 2019; 160:1480-1491. [PMID: 31083714 DOI: 10.1210/en.2019-00193] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 04/16/2019] [Indexed: 11/19/2022]
Abstract
A subpopulation of kisspeptin neurons located in the arcuate nucleus (ARN) operate as the GnRH pulse generator. The activity of this population of neurons can be monitored in real-time for long periods using kisspeptin neuron-selective GCaMP6 fiber photometry. Using this approach, we find that ARN kisspeptin neurons exhibit brief (∼50 seconds) periods of synchronized activity that precede pulses of LH in intact female mice. The dynamics and frequency of these synchronization episodes (SEs) are stable at approximately one event every 40 minutes throughout metestrus, diestrus, and proestrus, but slow considerably on estrus to occur approximately once every 10 hours. Evaluation of ARN kisspeptin neuron activity across the light-dark transition, including the time of onset of the proestrus LH surge, revealed no changes in SE frequency. Longer 24-hour recordings across proestrus into estrus demonstrated that an abrupt decrease in SEs occurred ∼4 to 5 hours after the onset of the LH surge to reach the low frequency of SEs observed on estrus. The frequency of SEs was stable across the 24-hour period from metestrus to diestrus. Administration of progesterone to diestrus mice resulted in the abrupt slowing of SEs. These observations show that the GnRH pulse generator exhibits an unvarying pattern of activity from metestrus through to the late evening of proestrus, at which time it slows dramatically, likely in response to postovulation progesterone secretion. The GnRH pulse generator maintains a constant frequency of activity across the time of the LH surge, demonstrating that it is not involved directly in surge generation.
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Affiliation(s)
- H James McQuillan
- Centre for Neuroendocrinology and Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, New Zealand
| | - Su Young Han
- Centre for Neuroendocrinology and Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, New Zealand
| | - Isaiah Cheong
- Centre for Neuroendocrinology and Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, New Zealand
| | - Allan E Herbison
- Centre for Neuroendocrinology and Department of Physiology, University of Otago School of Biomedical Sciences, Dunedin, New Zealand
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Irvine CH. The Nonpregnant Mare: A Review of Some Current Research and of the Last 25 Years of Endocrinology. Biol Reprod 2018. [DOI: 10.1093/biolreprod/52.monograph_series1.343] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Moenter SM. Leap of Faith: Does Serum Luteinizing Hormone Always Accurately Reflect Central Reproductive Neuroendocrine Activity? Neuroendocrinology 2015; 102:256-266. [PMID: 26278916 PMCID: PMC4675678 DOI: 10.1159/000438790] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 07/15/2015] [Indexed: 12/28/2022]
Abstract
The function of the central aspects of the hypothalamic-pituitary-gonadal axis has been assessed in a number of ways including direct measurements of the hypothalamic output and indirect measures using gonadotropin release from the pituitary as a bioassay for reproductive neuroendocrine activity. Here, methods for monitoring these various parameters are briefly reviewed and then examples presented of both concordance and discrepancy between central and peripheral measurements, with a focus on situations in which elevated gonadotropin-releasing hormone neurosecretion is not reflected accurately by pituitary luteinizing hormone release. Implications for the interpretation of gonadotropin data are discussed.
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Affiliation(s)
- Suzanne M Moenter
- Department of Molecular and Integrative Physiology, Internal Medicine, and Obstetrics and Gynecology, University of Michigan, Ann Arbor, Mich., USA
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Cholanian M, Krajewski-Hall SJ, Levine RB, McMullen NT, Rance NE. Electrophysiology of arcuate neurokinin B neurons in female Tac2-EGFP transgenic mice. Endocrinology 2014; 155:2555-65. [PMID: 24735328 PMCID: PMC4060187 DOI: 10.1210/en.2014-1065] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Neurons in the arcuate nucleus that coexpress kisspeptin, neurokinin B (NKB), and dynorphin (KNDy neurons) play an important role in the modulation of reproduction by estrogens. Here, we study the anatomical and electrophysiological properties of arcuate NKB neurons in heterozygous female transgenic mice with enhanced green fluorescent protein (EGFP) under the control of the Tac2 (NKB) promoter (Tac2-EGFP mice). The onset of puberty, estrous cyclicity, and serum LH were comparable between Tac2-EGFP and wild-type mice. The location of EGFP-immunoreactive neurons was consistent with previous descriptions of Tac2 mRNA-expressing neurons in the rodent. In the arcuate nucleus, nearly 80% of EGFP neurons expressed pro-NKB-immunoreactivity. Moreover, EGFP fluorescent intensity in arcuate neurons was increased by ovariectomy and reduced by 17β-estradiol (E2) treatment. Electrophysiology of single cells in tissue slices was used to examine the effects of chronic E2 treatment on Tac2-EGFP neurons in the arcuate nucleus of ovariectomized mice. Whole-cell recordings revealed arcuate NKB neurons to be either spontaneously active or silent in both groups. E2 had no significant effect on the basic electrophysiological properties or spontaneous firing frequencies. Arcuate NKB neurons exhibited either tonic or phasic firing patterns in response to a series of square-pulse current injections. Notably, E2 reduced the number of action potentials evoked by depolarizing current injections. This study demonstrates the utility of the Tac2-EGFP mouse for electrophysiological and morphological studies of KNDy neurons in tissue slices. In parallel to E2 negative feedback on LH secretion, E2 decreased the intensity of the EGFP signal and reduced the excitability of NKB neurons in the arcuate nucleus of ovariectomized Tac2-EGFP mice.
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Affiliation(s)
- Marina Cholanian
- Department of Pathology (M.C., S.J.K.-H.), University of Arizona College of Medicine, Tucson, Arizona 85724; Department of Neuroscience (R.B.L.), University of Arizona, Tucson, Arizona 85724; Department of Cellular and Molecular Medicine (N.T.M.), University of Arizona College of Medicine, Tucson, Arizona 85724; and Departments of Pathology and Neurology and the Evelyn F. McKnight Brain Institute (N.E.R.), University of Arizona College of Medicine, Tucson, Arizona 85724
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Uenoyama Y, Tsukamura H, Maeda KI. KNDy neuron as a gatekeeper of puberty onset. J Obstet Gynaecol Res 2014; 40:1518-26. [DOI: 10.1111/jog.12398] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 01/03/2014] [Indexed: 11/30/2022]
Affiliation(s)
| | - Hiroko Tsukamura
- Graduate School of Bioagricultural Sciences; Nagoya University; Nagoya
| | - Kei-ichiro Maeda
- Department of Veterinary; Medical Sciences; The University of Tokyo; Tokyo Japan
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Nestor CC, Kelly MJ, Rønnekleiv OK. Cross-talk between reproduction and energy homeostasis: central impact of estrogens, leptin and kisspeptin signaling. Horm Mol Biol Clin Investig 2014; 17:109-28. [PMID: 25372735 PMCID: PMC4959432 DOI: 10.1515/hmbci-2013-0050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 10/07/2013] [Indexed: 02/06/2023]
Abstract
The central nervous system receives hormonal cues (e.g., estrogens and leptin, among others) that influence reproduction and energy homeostasis. 17β-estradiol (E2) is known to regulate gonadotropin-releasing hormone (GnRH) secretion via classical steroid signaling and rapid non-classical membrane-initiated signaling. Because GnRH neurons are void of leptin receptors, the actions of leptin on these neurons must be indirect. Although it is clear that the arcuate nucleus of the hypothalamus is the primary site of overlap between these two systems, it is still unclear which neural network(s) participate in the cross-talk of E2 and leptin, two hormones essential for reproductive function and metabolism. Herein we review the progress made in understanding the interactions between reproduction and energy homeostasis by focusing on the advances made to understand the cellular signaling of E2 and leptin on three neural networks: kisspeptin, pro-opiomelanocortin (POMC) and neuropeptide Y (NPY). Although critical in mediating the actions of E2 and leptin, considerable work still remains to uncover how these neural networks interact in vivo.
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Affiliation(s)
- Casey C Nestor
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA
| | - Martin J. Kelly
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA; and Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA
| | - Oline K. Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA; and Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA
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Abstract
The ovulatory menstrual cycle is the result of the integrated action of the hypothalamus, pituitary, ovary, and endometrium. Like a metronome, the hypothalamus sets the beat for the menstrual cycle by the pulsatile release of gonadotropin-releasing hormone (GnRH). GnRH pulses occur every 1-1.5 h in the follicular phase of the cycle and every 2-4 h in the luteal phase of the cycle. Pulsatile GnRH secretion stimulates the pituitary gland to secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH). The pituitary gland translates the tempo set by the hypothalamus into a signal, LH and FSH secretion, that can be understood by the ovarian follicle. The ovarian follicle is composed of three key cells: theca cells, granulosa cells, and the oocyte. In the ovarian follicle, LH stimulates theca cells to produce androstenedione. In granulosa cells from small antral follicles, FSH stimulates the synthesis of aromatase (Cyp19) which catalyzes the conversion of theca-derived androstenedione to estradiol. A critical concentration of estradiol, produced from a large dominant antral follicle, causes positive feedback in the hypothalamus, likely through the kisspeptin system, resulting in an increase in GnRH secretion and an LH surge. The LH surge causes the initiation of the process of ovulation. After ovulation, the follicle is transformed into the corpus luteum, which is stimulated by LH or chorionic gonadotropin (hCG) should pregnancy occur to secrete progesterone. Progesterone prepares the endometrium for implantation of the conceptus. Estradiol stimulates the endometrium to proliferate. Estradiol and progesterone cause the endometrium to become differentiated to a secretory epithelium. During the mid-luteal phase of the cycle, when progesterone production is at its peak, the secretory endometrium is optimally prepared for the implantation of an embryo. A diagrammatic representation of the intricate interactions involved in coordinating the menstrual cycle is provided in Fig. 1.
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Affiliation(s)
- Robert L Barbieri
- Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St, Boston, MA, 02115, USA,
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Okamura H, Tsukamura H, Ohkura S, Uenoyama Y, Wakabayashi Y, Maeda KI. Kisspeptin and GnRH pulse generation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 784:297-323. [PMID: 23550012 DOI: 10.1007/978-1-4614-6199-9_14] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The reproductive neuropeptide gonadotropin-releasing hormone (GnRH) has two modes of secretion. Besides the surge mode, which induces ovulation in females, the pulse mode of GnRH release is essential to cause various reproductive events in both sexes, such as spermatogenesis, follicular development, and sex steroid synthesis. Some environmental cues control gonadal activities through modulating GnRH pulse frequency. Researchers have looked for the anatomical location of the mechanism generating GnRH pulses, the GnRH pulse generator, in the brain, because an artificial manipulation of GnRH pulse frequency is of therapeutic importance to stimulate or suppress gonadal activity. Discoveries of kisspeptin and, consequently, KNDy (kisspeptin/neurokinin B/dynorphin) neurons in the hypothalamus have provided a clue to the possible location of the GnRH pulse generator. Our analyses of hypothalamic multiple-unit activity revealed that KNDy neurons located in the hypothalamic arcuate nucleus might play a central role in the generation of GnRH pulses in goats, and perhaps other mammalian species. This chapter further discusses the possible mechanisms for GnRH pulse generation.
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Affiliation(s)
- Hiroaki Okamura
- National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
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Alçin E, Sahu A, Ramaswamy S, Hutz E, Keen K, Terasawa E, Bethea C, Plant T. Ovarian regulation of kisspeptin neurones in the arcuate nucleus of the rhesus monkey (macaca mulatta). J Neuroendocrinol 2013; 25:488-96. [PMID: 23331967 PMCID: PMC3928808 DOI: 10.1111/jne.12025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 01/03/2013] [Accepted: 01/10/2013] [Indexed: 11/28/2022]
Abstract
Tonic gonadotrophin secretion throughout the menstrual cycle is regulated by the negative-feedback actions of ovarian oestradiol (E₂) and progesterone. Although kisspeptin neurones in the arcuate nucleus (ARC) of the hypothalamus appear to play a major role in mediating these feedback actions of the steroids in nonprimate species, this issue has been less well studied in the monkey. In the present study, we used immunohistochemistry and in situ hybridisation to examine kisspeptin and KISS1 expression, respectively, in the mediobasal hypothalamus (MBH) of adult ovariectomised (OVX) rhesus monkeys. We also examined kisspeptin expression in the MBH of ovarian intact females, and the effect of E₂, progesterone and E₂ + progesterone replacement on KISS1 expression in OVX animals. Kisspeptin or KISS1 expressing neurones and pronounced kisspeptin fibres were readily identified throughout the ARC of ovariectomised monkeys but, on the other hand, in intact animals, kisspeptin cell bodies were small in size and number and only fine fibres were observed. Replacement of OVX monkeys with physiological levels of E₂, either alone or with luteal phase levels of progesterone, abolished KISS1 expression in the ARC. Interestingly, progesterone replacement alone for 14 days also resulted in a significant down-regulation of KISS1 expression. These findings support the view that, in primates, as in rodents and sheep, kisspeptin signalling in ARC neurones appears to play an important role in mediating the negative-feedback action of E₂ on gonadotrophin secretion, and also indicate the need to study further their regulation by progesterone.
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Affiliation(s)
- E. Alçin
- University of Pittsburgh, Department of Obstetrics, Gynecology and Reproductive Sciences, Magee-Womens Research Institute, Pittsburgh, PA 15213 USA
| | - A. Sahu
- University of Pittsburgh, Department of Obstetrics, Gynecology and Reproductive Sciences, Magee-Womens Research Institute, Pittsburgh, PA 15213 USA
| | - S. Ramaswamy
- University of Pittsburgh, Department of Obstetrics, Gynecology and Reproductive Sciences, Magee-Womens Research Institute, Pittsburgh, PA 15213 USA
| | - E.D. Hutz
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715 USA
| | - K.L. Keen
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715 USA
| | - E. Terasawa
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715 USA
- Department of Pediatrics, University of Wisconsin, Madison, WI 53715 USA
| | - C.L. Bethea
- Division of Reproductive Sciences and Neuroscience, Oregon National Primate Research Center, Beaverton, OR 97006 USA
| | - T.M. Plant
- University of Pittsburgh, Department of Obstetrics, Gynecology and Reproductive Sciences, Magee-Womens Research Institute, Pittsburgh, PA 15213 USA
- Corresponding author: Dr. Tony M. Plant, University of Pittsburgh, Dept. OB/GYN & Reprod Sci, Magee-Womens Research Institute, 204 Craft Avenue, Pittsburgh, PA 15213,
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Kelly MJ, Rønnekleiv OK. Membrane-initiated actions of estradiol that regulate reproduction, energy balance and body temperature. Front Neuroendocrinol 2012; 33:376-87. [PMID: 22871514 PMCID: PMC3618441 DOI: 10.1016/j.yfrne.2012.07.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 07/07/2012] [Accepted: 07/11/2012] [Indexed: 12/21/2022]
Abstract
It is well known that many of the actions of estrogens in the central nervous system are mediated via intracellular receptor/transcription factors that interact with steroid response elements on target genes. However, there now exists compelling evidence for membrane estrogen receptors in hypothalamic and other brain neurons. But, it is not well understood how estrogens signal via membrane receptors, and how these signals impact not only membrane excitability but also gene transcription in neurons. Indeed, it has been known for sometime that estrogens can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane delimited events. In addition, estrogens can affect second messenger systems including calcium mobilization and a plethora of kinases to alter cell signaling. Therefore, this review will consider our current knowledge of rapid membrane-initiated and intracellular signaling by estrogens in the hypothalamus, the nature of receptors involved and how they contribute to homeostatic functions.
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Affiliation(s)
- Martin J. Kelly
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR 97239
- Division of Neuroscience, Oregon Regional Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006
| | - Oline K. Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR 97239
- Division of Neuroscience, Oregon Regional Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR 97239
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Eghlidi DH, Haley GE, Noriega NC, Kohama SG, Urbanski HF. Influence of age and 17beta-estradiol on kisspeptin, neurokinin B, and prodynorphin gene expression in the arcuate-median eminence of female rhesus macaques. Endocrinology 2010; 151:3783-94. [PMID: 20519367 PMCID: PMC2940528 DOI: 10.1210/en.2010-0198] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Accepted: 05/06/2010] [Indexed: 11/19/2022]
Abstract
The neuropeptides kisspeptin, neurokinin B, and dynorphin A (collectively abbreviated as KNDy) are, respectively, encoded by KiSS-1, NKB, and PDYN and are coexpressed by neurons of the hypothalamic arcuate nucleus (ARC). Here, using quantitative real-time PCR, we examined age-related changes in the expression of genes encoding KNDy and associated receptors G protein-coupled receptor 54 (encoded by GPR54), neurokinin 3 receptor (encoded by NK3), and kappa-opioid receptor (encoded by KOR), in the female rhesus macaque ARC-median eminence (ARC-ME). Expression of KiSS-1 and NKB was highly elevated in old perimenopausal compared with young or middle-aged premenopausal animals. To test whether these age-related changes could be attributed to perimenopausal loss of sex steroids, we then examined KNDy, GPR54, NK3, and KOR expression changes in response to ovariectomy (OVX) and exposure to 17beta-estradiol (E(2)). Short-term (7 months) OVX (with or without 1 month of estrogen replacement) failed to modulate the expression of any of the KNDy-related genes. In contrast, long-term ( approximately 4 yr) OVX significantly increased KiSS-1 and NKB expression, and this was reversed by E(2) administration. Finally, we examined the expression of KNDy-related genes in young adult females during the early follicular, late follicular, or midluteal phases of their menstrual cycle but found no difference. Together, the results suggest that short-term alterations in circulating E(2) levels, such as those occurring during the menstrual cycle, may have little effect on the ARC-ME expression of KNDy and associated receptors. Nevertheless, they clearly demonstrate that loss of ovarian steroid negative feedback that occurs during perimenopause plays a major role in modulating the activity of KNDy circuits of the aging primate ARC-ME.
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Affiliation(s)
- Dominique H Eghlidi
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, Oregon 97006, USA
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Christian CA, Moenter SM. The neurobiology of preovulatory and estradiol-induced gonadotropin-releasing hormone surges. Endocr Rev 2010; 31:544-77. [PMID: 20237240 PMCID: PMC3365847 DOI: 10.1210/er.2009-0023] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Accepted: 02/18/2010] [Indexed: 12/14/2022]
Abstract
Ovarian steroids normally exert homeostatic negative feedback on GnRH release. During sustained exposure to elevated estradiol in the late follicular phase of the reproductive cycle, however, the feedback action of estradiol switches to positive, inducing a surge of GnRH release from the brain, which signals the pituitary LH surge that triggers ovulation. In rodents, this switch appears dependent on a circadian signal that times the surge to a specific time of day (e.g., late afternoon in nocturnal species). Although the precise nature of this daily signal and the mechanism of the switch from negative to positive feedback have remained elusive, work in the past decade has provided much insight into the role of circadian/diurnal and estradiol-dependent signals in GnRH/LH surge regulation and timing. Here we review the current knowledge of the neurobiology of the GnRH surge, in particular the actions of estradiol on GnRH neurons and their synaptic afferents, the regulation of GnRH neurons by fast synaptic transmission mediated by the neurotransmitters gamma-aminobutyric acid and glutamate, and the host of excitatory and inhibitory neuromodulators including kisspeptin, vasoactive intestinal polypeptide, catecholamines, neurokinin B, and RFamide-related peptides, that appear essential for GnRH surge regulation, and ultimately ovulation and fertility.
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Affiliation(s)
- Catherine A Christian
- Departments of Medicine and Cell Biology, University of Virginia, Charlottesville, 22908, USA.
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16
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Estradiol attenuates multiple tetrodotoxin-sensitive sodium currents in isolated gonadotropin-releasing hormone neurons. Brain Res 2010; 1345:137-45. [PMID: 20580637 DOI: 10.1016/j.brainres.2010.05.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Revised: 05/06/2010] [Accepted: 05/11/2010] [Indexed: 12/19/2022]
Abstract
Secretion from gonadotropin-releasing hormone (GnRH) neurons is necessary for the production of gametes and hormones from the gonads. Subsequently, GnRH release is regulated by steroid feedback. However, the mechanisms by which steroids, specifically estradiol, modulate GnRH secretion are poorly understood. We have previously shown that estradiol administered to the female mouse decreases inward currents in fluorescently labeled GnRH neurons. The purpose of this study was to examine the contribution of sodium currents in the negative feedback action of estradiol. Electrophysiology was performed on GnRH neurons dissociated from young, middle-aged, or old female mice. All mice were ovariectomized; half were estradiol replaced. The amplitude of the sodium current underlying the action potential was significantly decreased in GnRH neurons from young estradiol-treated animals. In addition, in vivo estradiol significantly decreased the transient sodium current amplitude, but prolonged the sodium current inactivation time constant. Estradiol decreased the persistent sodium current amplitude, and induced a significant negative shift in peak current potential. In contrast to results obtained from cells from young reproductive animals, estradiol did not significantly attenuate the sodium current underlying the action potential in cells isolated from middle-aged or old mice. Sodium channels can modulate cell threshold, latency of firing, and action potential characteristics. The reduction of sodium current amplitude by estradiol suggests a negative feedback on GnRH neurons, which could lead to a downregulation of cell excitability and hormone release. The attenuation of estradiol regulation in peripostreproductive and postreproductive animals could lead to dysregulated hormone release with advancing age.
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17
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Age- and sex-specific changes in naloxone-induced luteinizing hormone secretion and Fos expression in gonadotropin-releasing hormone neurons of gonadectomized rats. Neurosci Lett 2010; 471:157-61. [DOI: 10.1016/j.neulet.2010.01.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2009] [Revised: 12/29/2009] [Accepted: 01/15/2010] [Indexed: 11/23/2022]
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18
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McCartney CR, Blank SK, Marshall JC. Estradiol and progesterone-induced slowing of gonadotropin-releasing hormone pulse frequency is not reversed by subsequent administration of mifepristone. Endocrine 2009; 36:239-45. [PMID: 19609733 PMCID: PMC2758640 DOI: 10.1007/s12020-009-9215-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Accepted: 06/04/2009] [Indexed: 12/01/2022]
Abstract
Subsequent to suppression of LH (GnRH) pulse frequency by progesterone (P) and estradiol (E(2)), LH pulse frequency remains slow for 7 days after P withdrawal if mid-luteal E(2) concentrations are maintained. This may reflect an ability of E(2) to potentiate the suppressive effects of low P levels. We explored this notion in a similar experimental paradigm by administering a P-receptor antagonist (mifepristone) after P withdrawal while continuing E(2). Studies were performed in seven ovulatory, non-obese women. Transdermal E(2) (0.2 mg/day) and oral micronized P (100 mg every 8 h) were started within 24 h of the LH surge and continued for 10 days. Subjects then underwent a 13-h blood sampling protocol for determination of LH pulse characteristics and various hormone concentrations. Oral P was then discontinued, and oral mifepristone (50, 100, or 200 mg daily) and transdermal E(2) (0.2 mg/day) were administered for 7 days, after which the above sampling protocol was repeated. Results with all mifepristone doses were similar and therefore pooled. Mean LH, LH amplitude, and mean FSH markedly decreased after 7 days of mifepristone, but LH pulse frequency did not change (3.3 +/- 1.5 vs. 2.4 +/- 1.5 pulses/13 h). Prolactin and androstenedione increased between the first and second admissions, with no changes in E(2), cortisol, testosterone, or DHEAS. In conclusion, blockade of P action by mifepristone does not reverse a suppressed LH pulse frequency within 7 days when E(2) concentrations are maintained, suggesting that P withdrawal alone may not explain the luteal-follicular increase of GnRH pulse frequency.
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Affiliation(s)
- Christopher R McCartney
- Center for Research in Reproduction, University of Virginia Health System, Box 800391, Charlottesville, VA, 22908, USA.
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19
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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.
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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.
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20
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Affiliation(s)
- Suhail A R Doi
- Division of Endocrinology, Mubarak Al-Kabeer Hospital and Kuwait University, Kuwait.
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21
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Rometo AM, Krajewski SJ, Voytko ML, Rance NE. Hypertrophy and increased kisspeptin gene expression in the hypothalamic infundibular nucleus of postmenopausal women and ovariectomized monkeys. J Clin Endocrinol Metab 2007; 92:2744-50. [PMID: 17488799 DOI: 10.1210/jc.2007-0553] [Citation(s) in RCA: 256] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Human menopause is characterized by ovarian failure, gonadotropin hypersecretion, and neuronal hypertrophy in the hypothalamic infundibular (arcuate) nucleus. Recent studies have demonstrated a critical role for kisspeptins in reproductive regulation, but it is not known whether menopause is accompanied by changes in hypothalamic kisspeptin neurons. OBJECTIVES Our objective was to map the location of neurons expressing kisspeptin gene (KiSS-1) transcripts in the human hypothalamus and determine whether menopause is associated with changes in the size and gene expression of kisspeptin neurons. In monkeys, our objective was to evaluate the effects of ovariectomy and hormone replacement on neurons expressing KiSS-1 mRNA in the infundibular nucleus. SUBJECTS Hypothalamic tissues were collected at autopsy from eight premenopausal and nine postmenopausal women and from 42 young cynomolgus monkeys in various endocrine states. METHODS We used hybridization histochemistry, quantitative autoradiography, and computer-assisted microscopy. RESULTS Examination of human hypothalamic sections revealed that KiSS-1 neurons were located predominantly in the infundibular nucleus. In the infundibular nucleus of postmenopausal women, there was a significant increase in the size of neurons expressing KiSS-1 mRNA and the number of labeled cells and autoradiographic grains per neuron. Similar to postmenopausal women, ovariectomy induced neuronal hypertrophy and increased KiSS-1 gene expression in the monkey infundibular nucleus. Conversely, in ovariectomized monkeys, estrogen replacement markedly reduced KiSS-1 gene expression. CONCLUSIONS The cynomolgus monkey experiments provide strong evidence that the increase in KiSS-1 neuronal size and gene expression in postmenopausal women is secondary to ovarian failure. These studies suggest that kisspeptin neurons regulate estrogen negative feedback in the human.
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Affiliation(s)
- Adonna M Rometo
- Department of Pathology, University of Arizona College of Medicine, 1501 North Campbell Avenue, Tucson, Arizona 85724, USA
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22
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Doi SAR, Al-Zaid M, Towers PA, Scott CJ, Al-Shoumer KAS. Ovarian steroids modulate neuroendocrine dysfunction in polycystic ovary syndrome. J Endocrinol Invest 2005; 28:882-92. [PMID: 16419490 DOI: 10.1007/bf03345319] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
OBJECTIVE Neuroendocrine dysfunction in polycystic ovary syndrome (PCOS) was addressed by studying the steroid hormone changes in women with PCOS with either high or normal LH levels leading to inferences regarding the primacy of elevated LH in the pathophysiology of PCOS. METHODS A cross-sectional study was designed in an academic clinical facility involving 234 women with PCOS. Patients were divided into two groups based on an LH/FSH ratio < or >1 and hormonal and metabolic studies were performed in both groups. Factors were determined by binomial logistic regression that predicted group membership of these women. RESULTS Higher follicular phase estradiol (E2) and androstenedione (A4) levels as well as greater insulin sensitivity were the only factors that predicted the presence of neuroendocrine dysfunction with elevated A4 being necessary for neuroendocrine dysfunction. CONCLUSIONS It was concluded that uncoupling of hypothalamic E2 inhibition by elevated ovarian A4 associated with E2 related sensitization of pituitary LH leads to neuroendocrine dysfunction in PCOS.
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Affiliation(s)
- S A R Doi
- Division of Endocrinology, Mubarak Al-Kabeer Hospital and Department of Medicine, Faculty of Medicine, Kuwait University, Kuwait.
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23
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Mizuno M, Terasawa E. Search for neural substrates mediating inhibitory effects of oestrogen on pulsatile luteinising hormone-releasing hormone release in vivo in ovariectomized female rhesus monkeys (Macaca mulatta). J Neuroendocrinol 2005; 17:238-45. [PMID: 15842235 DOI: 10.1111/j.1365-2826.2005.01295.x] [Citation(s) in RCA: 27] [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: 11/27/2022]
Abstract
Neural substrates mediating the negative feedback effects of oestrogen on luteinising hormone-releasing hormone (LHRH) release were studied using the in vivo push-pull perfusion method in female rhesus monkeys. Twelve long-term ovariectomized female monkeys were implanted with Silastic capsules containing 17beta-oestradiol 2 weeks before the experiments and, on the day of the experiment, oestradiol benzoate (EB, 50 microg/kg) or oil was subcutaneously injected. Push-pull perfusate samples from the stalk-median eminence were collected in 10-min fractions from 4 h before to 18-20 h after EB or oil injection. LHRH and neuropeptide Y (NPY) levels in the same perfusates were measured by radioimmunoassay, and glutamate and GABA in the same perfusates were assessed by high-performance liquid chromatography (HPLC). The results indicate that EB significantly suppressed LHRH release (P < 0.005) starting within 2 h after EB, and continued for 18 h or until the experiment was terminated. Pulse analysis suggested that oestrogen suppressed the pulse amplitude, but not pulse frequency, of LHRH release. By contrast, EB did not alter any parameters (mean release, pulse amplitude or frequency) of pulsatile NPY release throughout the experiment. HPLC analysis further suggested that neither glutamate nor GABA levels in the stalk-median eminence were changed with oestrogen-induced LHRH suppression. Oil treatment did not alter LHRH, NPY, GABA and glutamate levels. It is concluded that oestrogen induces suppression of pulsatile LHRH release within 2 h, but the inhibitory effect of oestrogen on LHRH release does not appear to be mediated by NPY, GABAergic, or glutamatergic neurones.
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Affiliation(s)
- M Mizuno
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, WI 53715-1299, USA
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24
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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.
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Affiliation(s)
- Andrea C Gore
- University of Texas at Austin, Division of Pharmacology/Toxicology, Austin, Texas 78712, USA.
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25
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Nunemaker CS, DeFazio RA, Moenter SM. Estradiol-sensitive afferents modulate long-term episodic firing patterns of GnRH neurons. Endocrinology 2002; 143:2284-92. [PMID: 12021193 DOI: 10.1210/endo.143.6.8869] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GnRH neurons comprise the final common pathway of an estrogen-sensitive pattern generator controlling fertility. To determine estradiol effects on GnRH neuron firing patterns, adult transgenic mice were ovariectomized (OVX), and half were treated with estradiol (OVX+E). One week later targeted single-unit extracellular recordings were made from GnRH neurons identified by green fluorescent protein expression. Estradiol markedly affected GnRH neuron firing patterns, increasing the percentage and duration of time these cells were quiescent (< or = 1 action current/min). Estradiol increased the interval between episodes of increased firing rate determined by Cluster analysis of recordings more than 45 min (OVX+E 38.8 +/- 7.2 min, OVX 16.7 +/- 2.1 min, n = 6 each). Possible mechanisms of estradiol modulation were examined by simultaneously blocking ionotropic secretion of gamma-aminobutyric acid and glutamatergic receptors. This treatment had no effect on cells from OVX mice (n = 10), indicating episodic firing of GnRH neurons is not driven by activation of these receptors. Receptor blockade eliminated estradiol effects on GnRH neurons in the midventral preoptic area (n = 7) but not elsewhere (n = 7). Individual GnRH neurons thus display episodic firing patterns at intervals previously reported for secretory pulses. Estradiol modulates episode frequency to exert feedback control; in a substantial subset of GnRH neurons, estradiol feedback is enforced via GABAergic and/or glutamatergic afferents.
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Affiliation(s)
- Craig S Nunemaker
- Department of Internal Medicine and National Science Foundation Center for Biological Timing, University of Virginia, Charlottesville, Virginia 22908, USA
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26
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Pitts GR, Nunemaker CS, Moenter SM. Cycles of transcription and translation do not comprise the gonadotropin-releasing hormone pulse generator in GT1 cells. Endocrinology 2001; 142:1858-64. [PMID: 11316751 DOI: 10.1210/endo.142.5.8137] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Neural control of reproduction is achieved through episodic GnRH secretion, but little is known about the molecular mechanisms underlying pulse generation. The ultradian time domain of GnRH release suggests mechanisms ranging from macromolecular synthesis to posttranslational modification could be involved. We tested if messenger RNA (mRNA) or protein synthesis are components of the pulse generator by determining the effects of transcription and translation inhibitors on episodic GnRH release from immortalized GT1-1 GnRH neurons. Time course and efficacy of transcription and translation blockade were assessed by determining the ability of specific inhibitors to block the robust, rapid induction of c-fos mRNA or protein accumulation by forskolin (10 microM). The transcription inhibitors actinomycin D (ACT-D, 20 microM) or 5,6-dichlorobenzimidazole riboside (DRB, 100 microM), or the translation inhibitors anisomycin (ANI, 10 microM) or puromycin (PUR, 10 microM) were applied to GT1-1 cells 30, 15, or 0 min before forskolin. Northern and Western blots revealed blockade of transcription and translation was rapid and essentially complete. GT1-1 cells were perifused for a 90- to 120-min control period then for 100-130 min with vehicle or inhibitor to examine pulsatile GnRH secretion. GnRH interpeak intervals, peak amplitude, and peak area were not different between control and experimental periods of cells treated with vehicle (n = 15), ACT-D (n = 10), DRB (n = 6), ANI (n = 8), and PUR (n = 6; P > 0.05). This study presents the first clear evidence that the series of reactions resulting in secretion of a GnRH pulse do not include cycles of transcription and translation. Although these mechanisms would be required to replenish components of the pulse generator, they are not integral components of this oscillator. We hypothesize that posttranslational events underlie episodic GnRH release in GT1-1 cells.
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Affiliation(s)
- G R Pitts
- Departments of Internal Medicine, Cell Biology, and the National Science Foundation Center for Biological Timing, University of Virginia, Charlottesville, Virginia 22908
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27
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McGarvey C, Cates PA, Brooks A, Swanson IA, Milligan SR, Coen CW, O'Byrne KT. Phytoestrogens and gonadotropin-releasing hormone pulse generator activity and pituitary luteinizing hormone release in the rat. Endocrinology 2001; 142:1202-8. [PMID: 11181536 DOI: 10.1210/endo.142.3.8015] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Phytoestrogens can produce inhibitory effects on gonadotropin secretion in both animals and humans. The aims of this study were 2-fold: 1) to determine in vivo whether genistein and coumestrol act on the GnRH pulse generator to suppress hypothalamic multiunit electrical activity volleys and associated LH pulses and/or on the pituitary to suppress the LH response to GnRH; and 2) to examine the effect of these phytoestrogens on GnRH-induced pituitary LH release in vitro and to determine whether estrogen receptors are involved. Wistar rats were ovariectomized and chronically implanted with recording electrodes and/or indwelling cardiac catheters, and blood samples were taken every 5 min for 7--11 h. Intravenous infusion of coumestrol (1.6-mg bolus followed by 2.4 mg/h for 8.5 h) resulted in a profound inhibition of pulsatile LH secretion, a 50% reduction in the frequency of hypothalamic multiunit electrical activity volleys, and a complete suppression of the LH response to exogenous GnRH. In contrast, both genistein (1.6-mg bolus followed by 2.4 mg/h for 8.5 h) and vehicle were without effect on pulsatile LH secretion. Coumestrol (10(-5) M; over 2 or 4 h) suppressed GnRH-induced pituitary LH release in vitro, an effect blocked by the antiestrogen ICI 182,780. It is concluded that coumestrol acts centrally to reduce the frequency of the hypothalamic GnRH pulse generator. In addition, the inhibitory effects of coumestrol on LH pulses occur at the level of the pituitary by reducing responsiveness to GnRH via an estrogen receptor-mediated process.
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Affiliation(s)
- C McGarvey
- Division of Anatomy, Cell and Human Biology, Division of Physiology, GKT School of Biomedical Sciences, King's College London, Guy's Campus, London, United Kingdom SE1 1UL
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28
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Goodman RL, Thiery JC, Delaleu B, Malpaux B. Estradiol increases multiunit electrical activity in the A15 area of ewes exposed to inhibitory photoperiods. Biol Reprod 2000; 63:1352-7. [PMID: 11058538 DOI: 10.1095/biolreprod63.5.1352] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Seasonal anestrus in ewes results from an increase in response to the negative feedback action of estradiol (E(2)). This increase in the inhibitory effects of E(2) is controlled by photoperiod and appears to be mediated, in part, by dopaminergic neurons in the retrochiasmatic area of the hypothalamus (A15 group). This study was designed to test the hypothesis that E(2) increases multiunit electrical activity (MUA) in the A15 during inhibitory long days. MUA was monitored in the retrochiasmatic area of 14 ovariectomized ewes from 4 h before to 24 h after insertion of an E(2)-containing implant subcutaneously. In six of these ewes, MUA activity was also monitored before and after insertion of blank implants. Three of the 14 ewes were excluded from analysis because E(2) failed to inhibit LH. When MUA was recorded within the A15, E(2) produced a gradual increase in MUA that was sustained for 24 h. Blank implants failed to increase MUA in the A15 area, and E(2) did not alter MUA if recording electrodes were outside the A15. These data demonstrate that E(2) increases MUA in the A15 region of ewes and are consistent with the hypothesis that these neurons mediate E(2) negative feedback during long photoperiods.
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Affiliation(s)
- R L Goodman
- INRA, Physiologie de la Reproduction et des Comportements, 37380, Nouzilly, France.
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29
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Roy BN, Reid RL, Van Vugt DA. The effects of estrogen and progesterone on corticotropin-releasing hormone and arginine vasopressin messenger ribonucleic acid levels in the paraventricular nucleus and supraoptic nucleus of the rhesus monkey. Endocrinology 1999; 140:2191-8. [PMID: 10218971 DOI: 10.1210/endo.140.5.6684] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Ovarian steroids increase hypothalamic-pituitary-adrenal (HPA) axis activity and sensitize the hypothalamic-pituitary-ovarian (HPO) axis to stress-induced inhibition. The present study investigated the effect of ovarian steroids on CRH and arginine vasopressin (AVP) messenger RNA (mRNA) levels in the rhesus monkey hypothalamus, as both neuropeptides have been shown to stimulate the HPA axis and inhibit the HPO axis in this species. This was accomplished by measuring CRH and AVP mRNA in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) by in situ hybridization histochemistry. Menstrual cycles were simulated in ovariectomized (OVX) rhesus monkeys by sequential addition and removal of SILASTIC brand (Dow Corning Corp.) tubing containing either 17beta-estradiol (E2) or progesterone (P4). On the morning of day 11 of the simulated follicular phase (E2 alone) or day 21 of the luteal phase (E2 + P4), animals were anesthetized, and the brains were perfused with paraformaldehyde via the carotid artery. Coronal sections (30 microm) were cut, and mRNA for CRH and AVP in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) were semiquantified by in situ hybridization. CRH mRNA in the PVN of E2-replaced OVX animals (n = 7) was 2-fold greater than that in untreated OVX controls (n = 4), whereas CRH mRNA after E2 + P4 (n = 4) was no different from that in controls (optical density + SEM, 0.38 +/- 0.06, 0.13 +/- 0.08, and 0.14 +/- 0.09 for OVX + E2, OVX + E2 + P4, and OVX, respectively; P = 0.02). CRH in the SON was undetectable. In contrast to CRH, AVP mRNA in the PVN and the SON was similar in the three treatment groups. We conclude that E2 and E2 + P4 replacement to OVX monkeys exert different effects on CRH and AVP gene expression, as estrogen stimulation of CRH mRNA in the PVN was abrogated by progesterone, whereas no effect of ovarian steroids on AVP mRNA in either the PVN or SON was observed. We postulate that ovarian steroid regulation of CRH synthesis and release may in part explain the central nervous system mechanisms by which ovarian steroids affect the HPA and HPO axes during basal and stress conditions.
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Affiliation(s)
- B N Roy
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
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30
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Ordög T, Goldsmith JR, Chen MD, Connaughton MA, Hotchkiss J, Knobil E. On the mechanism of the positive feedback action of estradiol on luteinizing hormone secretion in the rhesus monkey. J Clin Endocrinol Metab 1998; 83:4047-53. [PMID: 9814490 DOI: 10.1210/jcem.83.11.5230] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In women and rhesus monkeys, both the negative and positive feedback actions of estradiol (E2) on gonadotropin secretion (inhibition followed by a surge) can be exerted directly at the level of the pituitary gland. We have tested the hypothesis that the positive feedback action of E2 represents but an "escape" from its negative feedback inhibition of gonadotropin secretion consequent to a desensitization of the gonadotropes occasioned by sustained exposure to elevated concentrations of the steroid. We have attempted to replicate such a desensitization by blocking the negative feedback action of E2 by the administration of a potent estrogen receptor antagonist devoid of any agonistic properties (ZM 182,780) to rhesus monkeys in the midfollicular phase of the menstrual cycle (n = 14). The estrogen antagonist, administered at a dose that in separate experiments completely blocked both the negative and the positive feedback effect of exogenous E2 on pituitary LH secretion, failed to produce a surge-like increase in serum LH concentrations. The present results do not support the hypothesis that the LH surge is the consequence of the removal of the negative feedback action of E2. Evidence is presented that ZM 182,780, in contrast to its inhibition of E2-induced LH surges, cannot block the inhibition of hypothalamic GnRH pulse generator activity by E2.
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Affiliation(s)
- T Ordög
- Department of Integrative Biology and Pharmacology, The University of Texas-Houston Medical School, 77225, USA
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Medina CL, Nagatani S, Darling TA, Bucholtz DC, Tsukamura H, Maeda K, Foster DL. Glucose availability modulates the timing of the luteinizing hormone surge in the ewe. J Neuroendocrinol 1998; 10:785-92. [PMID: 9792330 DOI: 10.1046/j.1365-2826.1998.00264.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To determine if glucose availability modulates the timing of the positive feedback action of oestrogen on gonadotropin secretion, we monitored the estradiol-induced luteinizing hormone (LH) surge in sheep (n = 5/group) made transiently hypoglycemic by insulin. Experiment 1 determined an effective insulin treatment, one which would depress tonic LH secretion. Two injections of insulin (5 IU/kg iv) 4 h apart were found to induce extended hypoglycemia (10-13 h) and to decrease the LH pulse frequency for 8 h (5.0 +/-0.32 pulses/4 h before versus 2.5+/-0.34 pulses/4 h after insulin; P<0.05; mean +/- SEM). Using this same paradigm, experiment 2 determined the influence of the transient hypoglycemia on the LH surge mechanism. In control sheep, estradiol (subcutaneous implants at hour 0) evoked an LH surge with a latency period of 12.4+/-0.5 h. When insulin was administered either before (hours -4 and 0) or after the estradiol stimulus (hours 4 and 8, or 12 and 16), the onset of the LH surge was delayed to 29.0+/-2.4 h (average of all three time groups, P <0.05). Infusion of glucose from hours 12-30, along with insulin, prevented hypoglycemia and restored the normal timing of the oestrogen-induced LH surge to that of controls (15.4+/-0.93 h, P>0.05). These findings suggest that not only is the tonic mode of LH secretion sensitive to metabolic fuel availability, but the surge mode of LH secretion is as well.
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Affiliation(s)
- C L Medina
- Reproductive Sciences Program, Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, USA
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32
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Affiliation(s)
- A E Herbison
- Laboratory of Neuroendocrinology, Babraham Institute, Cambridge, United Kingdom.
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33
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Zheng L, Krsmanovic LZ, Vergara LA, Catt KJ, Stojilkovic SS. Dependence of intracellular signaling and neurosecretion on phospholipase D activation in immortalized gonadotropin-releasing hormone neurons. Proc Natl Acad Sci U S A 1997; 94:1573-8. [PMID: 9037095 PMCID: PMC19833 DOI: 10.1073/pnas.94.4.1573] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The excitability of gonadotropin-releasing hormone (GnRH) neurons is essential for episodic neuropeptide release, but the mechanism by which electrical activity controls GnRH secretion is not well characterized. The role of phospholipase D (PLD) in mediating the activity-dependent secretory pathway was investigated in immortalized GT1 neurons, which both secrete GnRH and express GnRH receptors. Activation of these Ca2+-mobilizing receptors was associated with transient hyperpolarization of GT1 cells, followed by sustained firing of action potentials. This was accompanied by an increase in PLD activity, as indicated by elevated phosphatidylethanol (PEt) production. GnRH-induced PEt production was reduced by inhibition of phospholipase C-dependent phosphoinositide hydrolysis by U73122 and neomycin, suggesting that signaling from phospholipase C led to activation of PLD. The intermediate role of protein kinase C (PKC) in this process was indicated by the ability of phorbol 12-myristate 13-acetate to induce time- and dose-dependent increases in PEt and diacylglycerol, but not inositol trisphosphate, and by reduction of GnRH-induced PEt accumulation in PKC-depleted cells. Consistent with the role of action potential-driven Ca2+ entry in this process, agonist-induced PLD activity was also reduced by nifedipine and low extracellular Ca2+. Inhibition of the PLD pathway by ethanol and propranolol reduced diacylglycerol production and caused a concomitant fall in GnRH release. These data indicate that voltage-gated Ca2+ entry and PKC act in an independent but cooperative manner to regulate PLD activity, which contributes to the secretory response in GT1 cells. Thus, the electrical activity of the GnRH-secreting neuron participates in the functional coupling between GnRH receptors and PLD pathway.
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Affiliation(s)
- L Zheng
- Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Abstract
The hypothalamic gonadotropin-releasing hormone (GnRH) pulse generator presides over the pulsatile and feedback-regulated activities of the pituitary-gonadal axis. Awakening of synchronous activity of the GnRH neuronal ensemble in the earliest stages of puberty heralds the onset of full activation of the reproductive axis in girls and boys. Progression from prepuberty to adulthood in boys is directed by marked (30-fold) amplitude enhancement of pulsatile luteinizing hormone (LH) secretion, as assessed by an ultrasensitive immunofluorometric assay and deconvolution analysis. There is a much less apparent rise in LH secretory burst frequency (approximately 1.3-fold increase). Consequently, human puberty is an amplitude-driven neuroendocrine maturational process. However, less is known about pulsatile follicle-stimulating hormone (FSH) release in puberty. Multiple pathophysiologies that result in hypogonadotropic hypogonadism can converge on a final common mechanism of attenuated hypothalamic GnRH pulse generator output and hence reduced LH (and FSH) secretion. Disturbances may take the form of reduced GnRH pulse frequency and/or attenuated GnRH secretory burst mass. When the pathophysiology of hypogonadism originates exclusively in a failed GnRH pulse generator, then either treatment of the primary disease process where possible (e.g., by refeeding in starvation, improved metabolic control in diabetes mellitus, dopamine agonist treatment in hyperprolactinemia, etc) and/or treatment with pulsatile GnRH (e.g., in Kallmann's syndrome, isolated hypothalamic lesions, etc.) can provide relevant therapeutic options in children and adults.
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Affiliation(s)
- J D Veldhuis
- Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, USA
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Ordög T, Knobil E. Estradiol and the inhibition of hypothalamic gonadotropin-releasing hormone pulse generator activity in the rhesus monkey. Proc Natl Acad Sci U S A 1995; 92:5813-6. [PMID: 7597033 PMCID: PMC41591 DOI: 10.1073/pnas.92.13.5813] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In mammals, gonadal function is controlled by a hypothalamic signal generator that directs the pulsatile release of gonadotropin-releasing hormone (GnRH) and the consequent pulsatile secretion of luteinizing hormone. In female rhesus monkeys, the electrophysiological correlates of GnRH pulse generator activity are abrupt, rhythmic increases in hypothalamic multiunit activity (MUA volleys), which represent the simultaneous increase in firing rate of individual neurons. MUA volleys are arrested by estradiol, either spontaneously at midcycle or after the administration of the steroid. Multiunit recordings, however, provide only a measure of total neuronal activity, leaving the behavior of the individual cells obscure. This study was conducted to determine the mode of action of estradiol at the level of single neurons associated with the GnRH pulse generator. Twenty-three such single units were identified by cluster analysis of multiunit recordings obtained from a total of six electrodes implanted in the mediobasal hypothalamus of three ovariectomized rhesus monkeys, and their activity was monitored before and after estradiol administration. The bursting of all 23 units was arrested within 4 h of estradiol administration although their baseline activity was maintained. The bursts of most units reappeared at the same time as the MUA volleys, the recovery of some was delayed, and one remained inhibited for the duration of the study (43 days). The results indicate that estradiol does not desynchronize the bursting of single units associated with the GnRH pulse generator but that it inhibits this phenomenon. The site and mechanism of action of estradiol in this regard remain to be determined.
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Affiliation(s)
- T Ordög
- Laboratory for Neuroendocrinology, Medical School, University of Texas Health Science Center at Houston 77225, USA
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36
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Terasawa E. Control of luteinizing hormone-releasing hormone pulse generation in nonhuman primates. Cell Mol Neurobiol 1995; 15:141-64. [PMID: 7648606 DOI: 10.1007/bf02069563] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
1. The pulsatile release of luteinizing hormone-releasing hormone (LHRH) is critical for reproductive function. However, the exact mechanism of LHRH pulse generation is unclear. The purpose of this article is to review the current knowledge on LHRH pulse generation and to discuss a series of studies in our laboratory. 2. Using push-pull perfusion in the stalk-median eminence of the rhesus monkey several important facts have been revealed. There is evidence indicating that LHRH neurons themselves have endogenous pulse-generating mechanisms but that the pulsatility of LHRH release is also modulated by input from neuropeptide Y (NPY) and norepinephrine (NE) neurons. The release of NPY and NE is pulsatile, with their pulses preceding or occurring simultaneously with LHRH pulses, and the neuroligands NPY and NE and their agonists stimulate LHRH pulses, while the antagonists of the ligands suppress LHRH pulses. 3. The pulsatile release of LHRH increases during the estrogen-induced LH surge as well as the progesterone-induced LH surge. These increases are partly due to the stimulatory effects of estrogen and progesterone on NPY neurons. 4. An increase in pulsatile LHRH release occurs at the onset of puberty. This pubertal increase in LHRH release appears to be due to the removal of tonic inhibition from gamma aminobutyric acid (GABA) neurons and a subsequent increase in the inputs of NPY and NE neurons to LHRH neurons. 5. There are indications that additional neuromodulators are involved in the control of the LHRH pulse generation and that glia may play a role in coordinating pulses of the release of LHRH and neuromodulators. 6. It is concluded that the mechanism generating LHRH pulses appears to comprise highly complex cellular elements in the hypothalamus. The study of neuronal and nonneuronal elements of LHRH pulse generation may serve as a model to study the oscillatory behavior of neurosecretion.
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Affiliation(s)
- E Terasawa
- Wisconsin Regional Primate Research Center, University of Wisconsin-Madison 53715-1299, USA
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37
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Electrophysiological Analysis of GnRH Pulse Generator Activity in the Rhesus Monkey. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/b978-0-12-185289-4.50012-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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38
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Cardenas H, Ordög T, O'Byrne KT, Knobil E. Single unit components of the hypothalamic multiunit electrical activity associated with the central signal generator that directs the pulsatile secretion of gonadotropic hormones. Proc Natl Acad Sci U S A 1993; 90:9630-4. [PMID: 8415752 PMCID: PMC47623 DOI: 10.1073/pnas.90.20.9630] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Vertebrate reproduction is dependent on the operation of a central signal generator that directs the episodic release of gonadotropin-releasing hormone, a neuropeptide that stimulates secretion of the pituitary gonadotropic hormones and, thereby, controls gonadal function. The electrophysiological correlates of this pulse generator are characterized by abrupt increases in hypothalamic multiunit electrical activity (MUA volleys) invariably associated with the initiation of secretory episodes of luteinizing hormone. Using cluster analysis, we extracted single units from the multiunit signals recorded from the mediobasal hypothalamus of four intact and four ovariectomized rhesus monkeys. Of the 40 individual units identified in this manner, 24 increased their frequency with the MUA volleys. The onset and termination of these single-unit bursts occurred coincidently with those of the MUA volleys in both intact and ovariectomized animals, indicating that the longer duration of the MUA volleys characteristic of the gonadectomized animals was due not to the sequential activation of different units but to the longer bursts of the individual cells. Four other units showed decreases in firing rate during the MUA volleys, while the frequency of the remainder did not change. All the examined units were active during the intervals between the volleys of electrical activity. The results indicate that the MUA volleys associated with the activity of the gonadotropin-releasing hormone pulse generator represent the simultaneous increase in firing rate of some individual hypothalamic neurons and the decrease in the frequency of others.
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Affiliation(s)
- H Cardenas
- Laboratory for Neuroendocrinology, Medical School, University of Texas Health Science Center, Houston 77225
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Abstract
The female reproductive axis in mammals is a highly complex dynamic system which goes through different transient or absorbent states during the course of a life-time. Little is known about the mechanisms controlling this system during fetal life and at birth, although it has been shown in numerous species, including primates, that the whole machinery is already functioning (Brooks et al., 1990; Plant, 1986). After a delay ranging from a few days to a few weeks, according to the species, the reproductive axis becomes quiescent and activity apparently resumes only at the time of puberty. Here again understanding of the phenomenon is still limited (Ojeda, 1991).
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Affiliation(s)
- J C Thalabard
- URA CNRS 1454, Faculté Lyon-Sud, Chemin du Petit Revoyet, Oullins, France
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40
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Affiliation(s)
- E Knobil
- Laboratory for Neuroendocrinology, University of Texas Health Science Center, Medical School, Houston
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41
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Williams CL, Thalabard JC, O'Byrne KT, Grosser PM, Nishihara M, Hotchkiss J, Knobil E. Duration of phasic electrical activity of the hypothalamic gonadotropin-releasing hormone pulse generator and dynamics of luteinizing hormone pulses in the rhesus monkey. Proc Natl Acad Sci U S A 1990; 87:8580-2. [PMID: 2236069 PMCID: PMC55000 DOI: 10.1073/pnas.87.21.8580] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The secretion of luteinizing hormone (LH) by the pituitary gland is a pulsatile phenomenon. In the rhesus monkey, each pulse of LH in the peripheral circulation is associated with a characteristic increase in multiunit electrical activity (MUA) recorded from the medial basal hypothalamus. These "volleys" of electrical activity initiate the release of gonadotropin-releasing hormone (GnRH) into the pituitary portal circulation from the terminals of neurosecretory cells. Their duration varies from 1-3 min in normal, adult intact females to 10-25 min in long-term ovariectomized monkeys. A variety of pharmacological interventions also modify volley duration. The purpose of this investigation was to determine the physiological significance of alterations in volley duration. The dynamics of LH pulses in ovariectomized animals were observed in a number of experimental circumstances in which MUA volley duration was reduced from a maximum of 23 min to a minimum of 4 min without significantly altering their frequency. The magnitude of each LH pulse was assessed by calculating the area under the curve delineated by the time course of LH above baseline. In eight experiments, a linear regression of these values on volley duration failed to reveal a significant correlation between MUA volley duration and the magnitude of LH pulses. These results suggest that all of the GnRH secreted per pulse is released at the onset of each MUA volley, the remainder of the increase in electrical activity having no further action on GnRH secretion, although effects on other systems cannot be excluded.
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Affiliation(s)
- C L Williams
- Laboratory for Neuroendocrinology, University of Texas Medical School, Houston 77225
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42
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Wise PM, Weiland NG, Scarbrough K, Larson GH, Lloyd JM. Contribution of changing rhythmicity of hypothalamic neurotransmitter function to female reproductive aging. Ann N Y Acad Sci 1990; 592:31-43; discussion 44-51. [PMID: 1973887 DOI: 10.1111/j.1749-6632.1990.tb30314.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- P M Wise
- Department of Physiology, School of Medicine, University of Maryland, Baltimore 21201
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43
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Rossmanith WG, Liu CH, Laughlin GA, Mortola JF, Suh BY, Yen SS. Relative changes in LH pulsatility during the menstrual cycle: using data from hypogonadal women as a reference point. Clin Endocrinol (Oxf) 1990; 32:647-60. [PMID: 2364566 DOI: 10.1111/j.1365-2265.1990.tb00909.x] [Citation(s) in RCA: 39] [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: 12/31/2022]
Abstract
The basic premise of this study is that the GnRH-LH pulsatile activity, particularly its frequency characteristics, constitutes, in the absence of any considerable ovarian feedback, the intrinsic rhythm of the hypothalamic-pituitary unit at its maximal rate. Thus, LH pulse attributes determined in postpubertal hypogonadal subjects may be used as a reference in assessing the degree of influence exerted by endocrine factors that modulate GnRH-LH pulses. Accordingly, serum LH levels were determined in samples obtained at 15-min intervals for 24 h in 20 hypogonadal women: 13 postmenopausal women (PMW) and seven women with premature ovarian failure (POF). Similar measurements were performed in 60 normally cycling women: 25 in the early follicular phase (EFP), 13 in the late follicular phase (LFP), seven at midcycle surge (LH surge) and 15 in the midluteal phase (MLP). Significant pulses were identified by the cluster algorithm utilizing factors appropriate for 24 h data series of a sampling frequency of 15-min intervals. The results show a 24-h mean (+/- SE) LH pulse frequency of 78.2 +/- 2.8 and 85.5 +/- 2.4 min per pulse for young (POF) and older (PMW) hypogonadal women, respectively. During the follicular phase of the cycle, the LH pulse frequency is not significantly different from that of hypogonadal women, but there is a significant (P less than 0.05) increase from early to late follicular phases (95.4 +/- 3.3 vs 78.8 +/- 2.2 min per pulse). However, when the sleep periods are excluded from the 24-h data series because of the associated decrease of LH pulse frequency in EFP women, the resulting pulse frequencies are almost identical for EFP, LFP and PMW. An elevation beyond the basic pulse rhythm determined in PMW or POF is not observed in any phase of the menstrual cycle studied, including the midcycle surge. The decrease in LH pulse frequency during the luteal phase of the cycle (151.8 +/- 8.0 min per pulse, P less than 0.001 vs hypogonadal women) beyond the reference pulse frequency of hypogonadal women is unequivocal. By contrast, the pulse amplitude varies markedly among the groups with the largest found in POF (36.6 +/- 4.5 IU/l). It follows, in descending order, PMW (22.7 +/- 3.1 IU/l), midcycle surge (17.3 +/- 2.8 IU/l), MLP women (7.0 +/- 1.3 IU/l) and the EFP (4.9 +/- 0.3 IU/l) and LFP (4.0 +/- 0.4 IU/l).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- W G Rossmanith
- Department of Obstetrics-Gynecology, University of Ulm, FR Germany
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44
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Cagnacci A, Melis GB, Paoletti AM, Gambacciani M, Soldani R, Spinetti A, Fioretti P. Influence of oestradiol and progesterone on pulsatile LH secretion in postmenopausal women. Clin Endocrinol (Oxf) 1989; 31:541-50. [PMID: 2516785 DOI: 10.1111/j.1365-2265.1989.tb01278.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Pulsatile LH secretion was studied in six healthy postmenopausal women. Blood samples were obtained every 10 min during an 8-h saline infusion performed before and during the administration of transdermal oestradiol alone (E2; 50 micrograms/day) and in combination with vaginal progesterone (P; 100 mg twice daily). Plasma E2 and P levels reached values similar to those found in the early follicular phase and in the luteal phase of the menstrual cycle, respectively. The mean plasma LH levels significantly decreased (P less than 0.01) during transdermal E2 with and without vaginal P. A significant increase in the frequency (P less than 0.025) and the amplitude (P less than 0.05) of LH pulses was observed during transdermal E2. The administration of vaginal P to oestrongenized women significantly blunted the frequency (P less than 0.05) and enhanced the amplitude (P less than 0.05) of LH pulses. In all experimental conditions, the mean plasma LH levels showed a positive linear correlation with the amplitude of LH pulses. The present results show that peripheral levels of E2, similar to those of the early follicular phase of the menstrual cycle, can influence the pulsatile pattern of LH secretion, enhancing the frequency and the amplitude of LH pulses. In oestrogenized patients, the increase of peripheral P plasma levels to postovulatory values restored a pulsatile pattern of LH secretion similar to that of the early luteal phase of menstrual cycle.
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Affiliation(s)
- A Cagnacci
- Department of Obstetrics and Gynecology, University of Pisa School of Medicine, Italy
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45
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Devorshak-Harvey E, Bona-Gallo A, Gallo RV. Ovarian regulation of pulsatile luteinizing hormone secretion during late gestation in the rat*. J Neuroendocrinol 1989; 1:257-64. [PMID: 19210438 DOI: 10.1111/j.1365-2826.1989.tb00113.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Abstract The object of this study was to examine the influence of both estradiol (E(2)) and progesterone (P) alone or in combination on luteinizing hormone (LH) pulse amplitude and frequency during the interval between Days 21 and 22 of gestation. This was done by analyzing pulsatile LH release in rats bled on Days 21 and 22 of gestation, and in animals ovariectomized (OVX) on Day 21, implanted with silastic capsules producing plasma levels of E(2) and/or P characteristic of the Day 21 to 22 interval, and bled on Day 22 Pulsatile LH release increased between Days 21 and 22 due to an increase in pulse frequency and a small elevation in pulse amplitude. OVX produced no further increase in pulse frequency but markedly enhanced the small change in pulse amplitude. Preventing either the decline in plasma P that normally occurs between Days 21 and 22, or just the small additional decrease in plasma P levels produced by OVX, had no suppressive effect on pulse amplitude or frequency, although Day 22 levels of P alone augmented the normal increase in pulse frequency occurring between Days 21 and 22. Restoration of physiological plasma E(2) levels had no effect on the normal increase in pulse frequency, but partially attenuated the OVX-induced increase in pulse amplitude. Replacement of physiological Day 22 levels of both E(2) and P also decreased LH pulse amplitude, although amplitude was not significantly different from that seen following E(2) replacement alone, and was still greater than the normal Day 22 value. In contrast, restoration of physiological plasma levels of E(2)+ P caused a suppression of LH pulse frequency below that normally seen on Day 22. While E(2)+ P did not completely prevent the OVX-induced increase in pulse amplitude, administration of charcoal-extracted porcine follicular fluid to rats OVX on Day 21, and in which physiological plasma levels of E(2)+ P were restored, caused a further reduction in pulse amplitude. These data demonstrate that 1) marked increases in LH pulse amplitude are prevented from occurring between Days 21 and 22 of gestation by ovarian steroids, notably E(2), and that this suppression is enhanced by a non-steroidal factor present in porcine follicular fluid, 2) neither E(2) or P alone suppresses LH pulse frequency on Day 22 of gestation; LH pulse frequency increases on Day 22 because the plasma level of one of these steroids, P, markedly declines, and 3) restoration of physiological plasma levels of both steroids in the absence of the ovary produces an unphysiological suppression of pulse frequency, i.e. results in a lower pulse frequency than normally occurs in the presence of these same plasma steroid levels in animals with their ovaries intact. One hypothesis consistent with the latter observation is that at the end of gestation in the rat the ovary may produce a factor which 'protects' the frequency of the LH pulse generator from the negative feedback action of ovarian steroids. This allows an increase in LH pulse frequency and mean blood LH levels, and thereby facilitates ovarian follicular development and the normal progress of the first postpartum estrous cycle.
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Affiliation(s)
- E Devorshak-Harvey
- Department of Physiology and Neurobiology, The University of Connecticut, Storrs, Connecticut 06268, USA
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