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Dadam FM, Amigone JL, Vivas L, Macchione. Comparison of dipsogenic responses of adult rat offspring as a function of different perinatal programming models. Brain Res Bull 2022; 188:77-91. [PMID: 35882279 DOI: 10.1016/j.brainresbull.2022.07.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 07/12/2022] [Accepted: 07/20/2022] [Indexed: 11/30/2022]
Abstract
The perinatal environment interacts with the genotype of the developing organism resulting in a unique phenotype through a developmental or perinatal programming phenomenon. However, it remains unclear how this phenomenon differentially affects particular targets expressing specific drinking responses depending on the perinatal conditions. The main goal of the present study was to compare the dipsogenic responses induced by different thirst models as a function of two perinatal manipulation models, defined by the maternal free access to hypertonic sodium solution and a partial aortic ligation (PAL-W/Na) or a sham-ligation (Sham-W/Na). The programmed adult offspring of both perinatal manipulated models responded similarly when was challenged by overnight water dehydration or after a sodium depletion showing a reduced water intake in comparison to the non-programmed animals. However, when animals were evaluated after a body sodium overload, only adult Sham-W/Na offspring showed drinking differences compared to PAL and control offspring. By analyzing the central neurobiological substrates involved, a significant increase in the number of Fos + cells was found after sodium depletion in the subfornical organ of both programmed groups and an increase in the number of Fos + cells in the dorsal raphe nucleus was only observed in adult depleted PAL-W/Na. Our results suggest that perinatal programming is a phenomenon that differentially affects particular targets which induce specific dipsogenic responses depending on matching between perinatal programming conditions and the osmotic challenge in the latter environment. Probably, each programmed-drinking phenotype has a particular set point to elicit specific repertoires of mechanisms to reestablish fluid balance.
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Affiliation(s)
- F M Dadam
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - J L Amigone
- Sección de Bioquímica Clínica, Hospital Privado, Córdoba, Argentina
| | - L Vivas
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina; Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Macchione
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina.
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Wang YF, Parpura V. Astroglial Modulation of Hydromineral Balance and Cerebral Edema. Front Mol Neurosci 2018; 11:204. [PMID: 29946238 PMCID: PMC6007284 DOI: 10.3389/fnmol.2018.00204] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 05/22/2018] [Indexed: 12/11/2022] Open
Abstract
Maintenance of hydromineral balance (HB) is an essential condition for life activity at cellular, tissue, organ and system levels. This activity has been considered as a function of the osmotic regulatory system that focuses on hypothalamic vasopressin (VP) neurons, which can reflexively release VP into the brain and blood to meet the demand of HB. Recently, astrocytes have emerged as an essential component of the osmotic regulatory system in addition to functioning as a regulator of the HB at cellular and tissue levels. Astrocytes express all the components of osmoreceptors, including aquaporins, molecules of the extracellular matrix, integrins and transient receptor potential channels, with an operational dynamic range allowing them to detect and respond to osmotic changes, perhaps more efficiently than neurons. The resultant responses, i.e., astroglial morphological and functional plasticity in the supraoptic and paraventricular nuclei, can be conveyed, physically and chemically, to adjacent VP neurons, thereby influencing HB at the system level. In addition, astrocytes, particularly those in the circumventricular organs, are involved not only in VP-mediated osmotic regulation, but also in regulation of other osmolality-modulating hormones, including natriuretic peptides and angiotensin. Thus, astrocytes play a role in local/brain and systemic HB. The adaptive astrocytic reactions to osmotic challenges are associated with signaling events related to the expression of glial fibrillary acidic protein and aquaporin 4 to promote cell survival and repair. However, prolonged osmotic stress can initiate inflammatory and apoptotic signaling processes, leading to glial dysfunction and a variety of brain diseases. Among many diseases of brain injury and hydromineral disorders, cytotoxic and osmotic cerebral edemas are the most common pathological manifestation. Hyponatremia is the most common cause of osmotic cerebral edema. Overly fast correction of hyponatremia could lead to central pontine myelinolysis. Ischemic stroke exemplifies cytotoxic cerebral edema. In this review, we summarize and analyze the osmosensory functions of astrocytes and their implications in cerebral edema.
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Affiliation(s)
- Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin, China
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, United States
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Yang F, Zhou L, Qian X, Wang D, He WJ, Tang ZW, Yin J, Huang QY. Adropin Is a Key Mediator of Hypoxia Induced Anti-Dipsogenic Effects via TRPV4-CamKK-AMPK Signaling in the Circumventricular Organs of Rats. Front Mol Neurosci 2017; 10:105. [PMID: 28473751 PMCID: PMC5397471 DOI: 10.3389/fnmol.2017.00105] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 03/27/2017] [Indexed: 12/19/2022] Open
Abstract
Water intake reduction (anti-dipsogenic effects) under hypoxia has been well established, but the underlying reason remains unknown. Our previous report indicated that activated TRPV4 neurons in SFO are associated with anti-dipsogenic effects under hypoxia. Although low partial pressure of blood oxygen directly activates TRPV4, humoral factors could also be involved. In the present study, we hypothesize that adropin, a new endogenous peptide hormone, was rapidly increased (serum and brain) concomitant with reduced water intake in early hypoxia. Also, the nuclear expression of c-Fos, a marker for neuronal activation, related to water-consumption (SFO and MnPO) was inhibited. These effects were mitigated by a scavenger, rat adropin neutralizing antibody, which effectively neutralized adropin under hypoxia. Interestingly, injection of recombinant adropin in the third ventricle of the rats also triggered anti-dipsogenic effects and reduced c-Fos positive cells in SFO, but these effects were absent when TRPV4 was knocked down by shRNA. Moreover, adropin-activated CamKK-AMPK signaling related to TRPV4 calcium channel in SFO in normoxia. These results revealed that dissociative adropin was elevated in acute hypoxia, which was responsible for anti-dipsogenic effects by altering TRPV4-CamKK-AMPK signaling in SFO.
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Affiliation(s)
- Fan Yang
- Department of Pathophysiology and High Altitude Pathology, College of High Altitude Military Medicine, Third Military Medical UniversityChongqing, China.,Key Laboratory of High Altitude Medicine, Third Military Medical University, Ministry of EducationChongqing, China.,Key Laboratory of High Altitude Medicine, PLA, Third Military Medical UniversityChongqing, China
| | - Li Zhou
- Department of Pharmacy, Xinqiao Hospital and The Second Affiliated Hospital, The Third Military Medical UniversityChongqing, China
| | - Xu Qian
- Ba Gong li Sanatorium, The Chinese People's Liberation Army 77200 TroopsKunming, China
| | - Dong Wang
- Department of Pathophysiology and High Altitude Pathology, College of High Altitude Military Medicine, Third Military Medical UniversityChongqing, China.,Key Laboratory of High Altitude Medicine, Third Military Medical University, Ministry of EducationChongqing, China.,Key Laboratory of High Altitude Medicine, PLA, Third Military Medical UniversityChongqing, China
| | - Wen-Juan He
- Department of Pathophysiology and High Altitude Pathology, College of High Altitude Military Medicine, Third Military Medical UniversityChongqing, China.,Key Laboratory of High Altitude Medicine, Third Military Medical University, Ministry of EducationChongqing, China.,Key Laboratory of High Altitude Medicine, PLA, Third Military Medical UniversityChongqing, China
| | - Zhong-Wei Tang
- Department of Pathophysiology and High Altitude Pathology, College of High Altitude Military Medicine, Third Military Medical UniversityChongqing, China.,Key Laboratory of High Altitude Medicine, Third Military Medical University, Ministry of EducationChongqing, China.,Key Laboratory of High Altitude Medicine, PLA, Third Military Medical UniversityChongqing, China
| | - Jun Yin
- Department of Pathophysiology and High Altitude Pathology, College of High Altitude Military Medicine, Third Military Medical UniversityChongqing, China.,Key Laboratory of High Altitude Medicine, Third Military Medical University, Ministry of EducationChongqing, China.,Key Laboratory of High Altitude Medicine, PLA, Third Military Medical UniversityChongqing, China
| | - Qing-Yuan Huang
- Department of Pathophysiology and High Altitude Pathology, College of High Altitude Military Medicine, Third Military Medical UniversityChongqing, China.,Key Laboratory of High Altitude Medicine, Third Military Medical University, Ministry of EducationChongqing, China.,Key Laboratory of High Altitude Medicine, PLA, Third Military Medical UniversityChongqing, China
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Kawano H. Synaptic contact between median preoptic neurons and subfornical organ neurons projecting to the paraventricular hypothalamic nucleus. Exp Brain Res 2017; 235:1053-1062. [DOI: 10.1007/s00221-016-4862-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 12/20/2016] [Indexed: 11/28/2022]
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5
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CNS sites activated by renal pelvic epithelial sodium channels (ENaCs) in response to hypertonic saline in awake rats. Auton Neurosci 2016; 204:35-47. [PMID: 27717709 DOI: 10.1016/j.autneu.2016.09.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 09/17/2016] [Accepted: 09/19/2016] [Indexed: 12/18/2022]
Abstract
In some patients, renal nerve denervation has been reported to be an effective treatment for essential hypertension. Considerable evidence suggests that afferent renal nerves (ARN) and sodium balance play important roles in the development and maintenance of high blood pressure. ARN are sensitive to sodium concentrations in the renal pelvis. To better understand the role of ARN, we infused isotonic or hypertonic NaCl (308 or 500mOsm) into the left renal pelvis of conscious rats for two 2hours while recording arterial pressure and heart rate. Subsequently, brain tissue was analyzed for immunohistochemical detection of the protein Fos, a marker for neuronal activation. Fos-immunoreactive neurons were identified in numerous sites in the forebrain and brainstem. These areas included the nucleus tractus solitarius (NTS), the lateral parabrachial nucleus, the paraventricular nucleus of the hypothalamus (PVH) and the supraoptic nucleus (SON). The most effective stimulus was 500mOsm NaCl. Activation of these sites was attenuated or prevented by administration of benzamil (1μM) or amiloride (10μM) into the renal pelvis concomitantly with hypertonic saline. In anesthetized rats, infusion of hypertonic saline but not isotonic saline into the renal pelvis elevated ARN activity and this increase was attenuated by simultaneous infusion of benzamil or amiloride. We propose that renal pelvic epithelial sodium channels (ENaCs) play a role in activation of ARN and, via central visceral afferent circuits, this system modulates fluid volume and peripheral blood pressure. These pathways may contribute to the development of hypertension.
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Dampney RAL. Central neural control of the cardiovascular system: current perspectives. ADVANCES IN PHYSIOLOGY EDUCATION 2016; 40:283-296. [PMID: 27445275 DOI: 10.1152/advan.00027.2016] [Citation(s) in RCA: 151] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 05/23/2016] [Indexed: 06/06/2023]
Abstract
This brief review, which is based on a lecture presented at the American Physiological Society Teaching Refresher Course on the Brain and Systems Control as part of the Experimental Biology meeting in 2015, aims to summarize current concepts of the principal mechanisms in the brain that regulate the autonomic outflow to the cardiovascular system. Such cardiovascular regulatory mechanisms do not operate in isolation but are closely coordinated with respiratory and other regulatory mechanisms to maintain homeostasis. The brain regulates the cardiovascular system by two general means: 1) feedforward regulation, often referred to as "central command," and 2) feedback or reflex regulation. In most situations (e.g., during exercise, defensive behavior, sleep, etc.), both of these general mechanisms contribute to overall cardiovascular homeostasis. The review first describes the mechanisms and central circuitry subserving the baroreceptor, chemoreceptor, and other reflexes that work together to regulate an appropriate level of blood pressure and blood oxygenation and then considers the brain mechanisms that defend the body against more complex environmental challenges, using dehydration and cold and heat stress as examples. The last section of the review considers the central mechanisms regulating cardiovascular function associated with different behaviors, with a specific focus on defensive behavior and exercise.
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Affiliation(s)
- Roger A L Dampney
- School of Medical Sciences (Physiology) and Bosch Institute, The University of Sydney, Sydney, New South Wales, Australia
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Graebner AK, Iyer M, Carter ME. Understanding how discrete populations of hypothalamic neurons orchestrate complicated behavioral states. Front Syst Neurosci 2015; 9:111. [PMID: 26300745 PMCID: PMC4523943 DOI: 10.3389/fnsys.2015.00111] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 07/16/2015] [Indexed: 01/01/2023] Open
Abstract
A major question in systems neuroscience is how a single population of neurons can interact with the rest of the brain to orchestrate complex behavioral states. The hypothalamus contains many such discrete neuronal populations that individually regulate arousal, feeding, and drinking. For example, hypothalamic neurons that express hypocretin (Hcrt) neuropeptides can sense homeostatic and metabolic factors affecting wakefulness and orchestrate organismal arousal. Neurons that express agouti-related protein (AgRP) can sense the metabolic needs of the body and orchestrate a state of hunger. The organum vasculosum of the lamina terminalis (OVLT) can detect the hypertonicity of blood and orchestrate a state of thirst. Each hypothalamic population is sufficient to generate complicated behavioral states through the combined efforts of distinct efferent projections. The principal challenge to understanding these brain systems is therefore to determine the individual roles of each downstream projection for each behavioral state. In recent years, the development and application of temporally precise, genetically encoded tools has greatly improved our understanding of the structure and function of these neural systems. This review will survey recent advances in our understanding of how these individual hypothalamic populations can orchestrate complicated behavioral states due to the combined efforts of individual downstream projections.
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Affiliation(s)
- Allison K Graebner
- Program in Neuroscience, Department of Biology, Williams College Williamstown, MA, USA
| | - Manasi Iyer
- Program in Neuroscience, Department of Biology, Williams College Williamstown, MA, USA
| | - Matthew E Carter
- Program in Neuroscience, Department of Biology, Williams College Williamstown, MA, USA
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8
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Macchione AF, Beas C, Dadam FM, Caeiro XE, Godino A, Ponce LF, Amigone JL, Vivas L. Early free access to hypertonic NaCl solution induces a long-term effect on drinking, brain cell activity and gene expression of adult rat offspring. Neuroscience 2015; 298:120-36. [PMID: 25872186 DOI: 10.1016/j.neuroscience.2015.04.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 04/03/2015] [Accepted: 04/03/2015] [Indexed: 12/20/2022]
Abstract
Exposure to an altered osmotic environment during a pre/postnatal period can differentially program the fluid intake and excretion pattern profile in a way that persists until adulthood. However, knowledge about the programming effects on the underlying brain neurochemical circuits of thirst and hydroelectrolyte balance, and its relation with behavioral outputs, is limited. We evaluated whether early voluntary intake of hypertonic NaCl solution may program adult offspring fluid balance, plasma vasopressin, neural activity, and brain vasopressin and angiotensinergic receptor type 1a (AT1a)-receptor gene expression. The manipulation (M) period covered dams from 1 week before conception until offspring turned 1-month-old. The experimental groups were (i) Free access to hypertonic NaCl solution (0.45 M NaCl), food (0.18% NaCl) and water [M-Na]; and (ii) Free access to food and water only [M-Ctrol]. Male offspring (2-month-old) were subjected to iv infusion (0.15 ml/min) of hypertonic (1.5M NaCl), isotonic (0.15M NaCl) or sham infusion during 20 min. Cumulative water intake (140 min) and drinking latency to the first lick were recorded from the start of the infusion. Our results indicate that, after systemic sodium overload, the M-Na group had increased water intake, and diminished neuronal activity (Fos-immunoreactivity) in the subfornical organ (SFO) and nucleus of the solitary tract. They also showed reduced relative vasopressin (AVP)-mRNA and AT1a-mRNA expression at the supraoptic nucleus and SFO, respectively. The data indicate that the availability of a rich source of sodium during the pre/postnatal period induces a long-term effect on drinking, neural activity, and brain gene expression implicated in the control of hydroelectrolyte balance.
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Affiliation(s)
- A F Macchione
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina; Facultad de Odontología, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - C Beas
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - F M Dadam
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - X E Caeiro
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - A Godino
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - L F Ponce
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - J L Amigone
- Sección de Bioquímica Clínica, Hospital Privado, Córdoba, Argentina
| | - L Vivas
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina; Facultad de Odontología, Universidad Nacional de Córdoba, Córdoba, Argentina; Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina.
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Coble JP, Grobe JL, Johnson AK, Sigmund CD. Mechanisms of brain renin angiotensin system-induced drinking and blood pressure: importance of the subfornical organ. Am J Physiol Regul Integr Comp Physiol 2014; 308:R238-49. [PMID: 25519738 DOI: 10.1152/ajpregu.00486.2014] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is critical for cells to maintain a homeostatic balance of water and electrolytes because disturbances can disrupt cellular function, which can lead to profound effects on the physiology of an organism. Dehydration can be classified as either intra- or extracellular, and different mechanisms have developed to restore homeostasis in response to each. Whereas the renin-angiotensin system (RAS) is important for restoring homeostasis after dehydration, the pathways mediating the responses to intra- and extracellular dehydration may differ. Thirst responses mediated through the angiotensin type 1 receptor (AT1R) and angiotensin type 2 receptors (AT2R) respond to extracellular dehydration and intracellular dehydration, respectively. Intracellular signaling factors, such as protein kinase C (PKC), reactive oxygen species (ROS), and the mitogen-activated protein (MAP) kinase pathway, mediate the effects of central angiotensin II (ANG II). Experimental evidence also demonstrates the importance of the subfornical organ (SFO) in mediating some of the fluid intake effects of central ANG II. The purpose of this review is to highlight the importance of the SFO in mediating fluid intake responses to dehydration and ANG II.
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Affiliation(s)
| | - Justin L Grobe
- Department of Pharmacology, Center for Hypertension Research, Roy J. and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | | | - Curt D Sigmund
- Department of Pharmacology, Center for Hypertension Research, Roy J. and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa
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Stone S, Bibens M, Jones A, Curtis K. Running longer, running stronger: a brief review of endurance exercise and oestrogen. COMPARATIVE EXERCISE PHYSIOLOGY 2014. [DOI: 10.3920/cep140007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Athletic performance in endurance exercise is determined by an interplay among many physiological factors. Body fluid regulation, influenced by both hormonal and osmotic stimuli, is particularly important for maximising performance in endurance sports, as dehydration markedly decreases endurance. Oestrogen has a broad range of effects on the regulation of body fluid balance, as well as on aerobic capacity, metabolism, and other factors that impact endurance exercise performance, yet the role of oestrogen in endurance exercise performance has not been thoroughly examined. This review discusses the effects of oestrogen on compensatory hormonal and behavioural responses to dehydration, such as renin-angiotensin-aldosterone system activation and thirst, that restore body fluid balance and thereby affect exercise performance. Oestrogen-mediated effects and their potential consequences for endurance performance are also evaluated in the context of thermoregulation and aerobic capacity, as well as substrate utilisation during exercise. In addressing the role of oestrogen in endurance exercise, this review will examine human and animal models of endurance exercise and discuss similarities, differences, and limitations. Our aim is to integrate research from neuroscience, physiology, and exercise science to advance understanding of how oestrogen may impact exercise. Such understanding will have particularly important implications for female endurance athletes experiencing the hormonal fluctuations that occur during the reproductive cycle.
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Affiliation(s)
- S.A. Stone
- Mary Baldwin College, 318 Prospect St., Staunton, VA 24401, USA
| | - M.E. Bibens
- Oklahoma State University, Center for Health Sciences, 1111 West 17th Street, Tulsa, OK 74107, USA
| | - A.B. Jones
- Oklahoma State University, Center for Health Sciences, 1111 West 17th Street, Tulsa, OK 74107, USA
| | - K.S. Curtis
- Oklahoma State University, Center for Health Sciences, 1111 West 17th Street, Tulsa, OK 74107, USA
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Miller RL, Wang MH, Gray PA, Salkoff LB, Loewy AD. ENaC-expressing neurons in the sensory circumventricular organs become c-Fos activated following systemic sodium changes. Am J Physiol Regul Integr Comp Physiol 2013; 305:R1141-52. [PMID: 24049115 DOI: 10.1152/ajpregu.00242.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The sensory circumventricular organs (CVOs) are specialized collections of neurons and glia that lie in the midline of the third and fourth ventricles of the brain, lack a blood-brain barrier, and function as chemosensors, sampling both the cerebrospinal fluid and plasma. These structures, which include the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and area postrema (AP), are sensitive to changes in sodium concentration but the cellular mechanisms involved remain unknown. Epithelial sodium channel (ENaC)-expressing neurons of the CVOs may be involved in this process. Here we demonstrate with immunohistochemical and in situ hybridization methods that ENaC-expressing neurons are densely concentrated in the sensory CVOs. These neurons become c-Fos activated, a marker for neuronal activity, after various manipulations of peripheral levels of sodium including systemic injections with hypertonic saline, dietary sodium deprivation, and sodium repletion after prolonged sodium deprivation. The increases seen c-Fos activity in the CVOs were correlated with parallel increases in plasma sodium levels. Since ENaCs play a central role in sodium reabsorption in kidney and other epithelia, we present a hypothesis here suggesting that these channels may also serve a related function in the CVOs. ENaCs could be a significant factor in modulating CVO neuronal activity by controlling the magnitude of sodium permeability in neurons. Hence, some of the same circulating hormones controlling ENaC expression in kidney, such as angiotensin II and atrial natriuretic peptide, may coordinate ENaC expression in sensory CVO neurons and could potentially orchestrate sodium appetite, osmoregulation, and vasomotor sympathetic drive.
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Affiliation(s)
- Rebecca L Miller
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
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12
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Hindmarch CCT, Fry M, Smith PM, Yao ST, Hazell GGJ, Lolait SJ, Paton JFR, Ferguson AV, Murphy D. The transcriptome of the medullary area postrema: the thirsty rat, the hungry rat and the hypertensive rat. Exp Physiol 2011; 96:495-504. [DOI: 10.1113/expphysiol.2010.056515] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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13
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Colombari E, Colombari DSA, Li H, Shi P, Dong Y, Jiang N, Raizada MK, Sumners C, Murphy D, Paton JFR. Macrophage migration inhibitory factor in the paraventricular nucleus plays a major role in the sympathoexcitatory response to salt. Hypertension 2010; 56:956-63. [PMID: 20937969 DOI: 10.1161/hypertensionaha.110.155101] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Central hyperosmotic stimulation (HS) evokes increases in sympathetic nerve activity mediated by activation of angiotensin type 1 receptors in the hypothalamic paraventricular nucleus (PVN). Macrophage inhibitory migration factor (MIF) is an intracellular inhibitory regulator of angiotensin type 1 receptor-mediated actions of angiotensin II within neurons of the PVN. MIF mediates its actions via its intrinsic thiol-protein oxidoreductase activity. We demonstrate that intracerebroventricular injection of hypertonic saline into Sprague-Dawley rats elicits a significant (≈112%) increase in MIF mRNA expression in the PVN. Next, we evaluated the effect of viral-mediated expression of either MIF or [C60S]-MIF (which lacks thiol-protein oxidoreductase activity) in the PVN on the sympathoexcitation evoked by HS. We used a decorticate, arterially perfused in situ preparation of male Wistar rats (60 to 80 g). HS was induced by raising perfusate osmolality from 290 to 380 milliosmoles for 40 seconds. Seven to 10 days before experiments, rats were injected bilaterally (500 nL per side) with 0.9% saline (control) or with adenoassociated virus to express MIF, [C60S]-MIF, or enhanced green fluorescent protein in the PVN. HS produced sympathoexcitation in both the 0.9% saline and enhanced green fluorescent protein groups (sympathetic nerve activity increase of +27±4% and +25±4%, respectively; P<0.05), an effect that was not observed in the MIF group (+4±5%). Conversely, the HS-induced increase in sympathetic nerve activity was potentiated in the [C60S]-MIF group (+45±6%; P<0.05). We propose that MIF acting within the PVN is a major counterregulator of HS-induced sympathoexcitation, an effect that depends on thiol-protein oxidoreductase activity.
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Affiliation(s)
- Eduardo Colombari
- School of Physiology and Pharmacology, Bristol Heart Institute, University of Bristol, Bristol, UK
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14
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Yuan H, Gao B, Duan L, Jiang S, Cao R, Xiong YF, Rao ZR. Acute hyperosmotic stimulus-induced Fos expression in neurons depends on activation of astrocytes in the supraoptic nucleus of rats. J Neurosci Res 2010; 88:1364-73. [PMID: 19938175 DOI: 10.1002/jnr.22297] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Acute hyperosmolarity induced a time-dependent expression of Fos protein in both neurons and astrocytes of the rat supraoptic nucleus, with peak Fos expression occurring at 45 min in astrocytes and at 90 min in neurons after hypertonic stimulation in vivo. To determine whether the two cell types were activated separately or in an integrated manner, animals were pretreated with fluorocitrate, a glial metabolic blocker or carbenoxolone, a gap junction blocker followed by an acute hypertonic stimulation similar to that of the controls. Antibodies against glial fibrillary acidic protein, connexin 43, vasopressin, and oxytocin were used in serial sections to identify the cellular elements of the supraoptic nucleus. It was found that interruption of astrocyte metabolism with fluorocitrate significantly reduced Fos protein expression in both astrocytes and neurons, whereas blockage of gap junctions with carbenoxolone clearly reduced Fos protein expression in neurons, but not in astrocytes. These results indicate that both neurons and astrocytes in the rat supraoptic nucleus are involved in regulating osmolarity. Astrocytes are activated first, whereas connexin 43 functional hemichannels in SON astrocytes are required for the subsequent activation of the neurons.
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Affiliation(s)
- Hua Yuan
- Institute of Neuroscience, The Fourth Military Medical University, Xi'an, China
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Shi P, Martinez MA, Calderon AS, Chen Q, Cunningham JT, Toney GM. Intra-carotid hyperosmotic stimulation increases Fos staining in forebrain organum vasculosum laminae terminalis neurones that project to the hypothalamic paraventricular nucleus. J Physiol 2008; 586:5231-45. [PMID: 18755745 DOI: 10.1113/jphysiol.2008.159665] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Body fluid hyperosmolality has long been known to elicit homeostatic responses that range from drinking to inhibition of salt appetite to release of neurohypohyseal hormones (i.e. vasopressin and oxytocin). More recently, it has been recognized that hyperosmolality is capable of also provoking a significant increase of sympathetic nerve activity (SNA). It has been reported that neurones in the forebrain organum vasculosum laminae terminalis (OVLT) and hypothalamic paraventricular nucleus (PVN) each contribute significantly to this response. Here we sought to determine if sympathoexcitatory levels of hyperosmolality activate specifically those OVLT neurones that form a monosynaptic pathway to the PVN. First, we established in anaesthetized rats that graded concentrations of hypertonic NaCl (1.5 and 3.0 osmol kg(-1)) elicit graded increases of renal SNA (RSNA) when infused at a rate of 0.1 ml min(-1) through an internal carotid artery (ICA) - the major vascular supply of the forebrain. Next, infusions were performed in conscious rats in which OVLT neurones projecting to the PVN (OVLT-PVN) were retrogradely labelled with cholera toxin subunit B (CTB). Immunostaining of the immediate early gene product Fos and CTB was performed to quantify osmotic activation of OVLT-PVN neurones. ICA infusions of hypertonic NaCl and mannitol each significantly (P < 0.01-0.001) increased the number of Fos immunoreactive (Fos-ir) neuronal nuclei in the dorsal cap (DC) and lateral margins (LM) of OVLT. In the LM, infusions of 1.5 and 3.0 osmol kg(-1) NaCl produced similar increases in the number of Fos-ir neurones. In the DC, these infusions produced graded increases in Fos expression. Among OVLT neurones with axons projecting directly to the PVN (i.e. CTB-ir), graded hypertonic NaCl infusions again produced graded increases in Fos expression and this was observed in both the DC and LM. Although the DC and LM contained a similar number of OVLT-PVN neurones, the proportion of such neurones that expressed Fos-ir in responses to ICA hypertonic NaCl infusions was greater in the DC (P < 0.001). These findings support the conclusion that PVN-projecting neurones in the DC and LM of OVLT could participate in behavioural, neuroendocrine, and sympathetic nervous system responses to body fluid hyperosmolality.
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Affiliation(s)
- Peng Shi
- Department of Physiology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
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Shi P, Stocker SD, Toney GM. Organum vasculosum laminae terminalis contributes to increased sympathetic nerve activity induced by central hyperosmolality. Am J Physiol Regul Integr Comp Physiol 2007; 293:R2279-89. [PMID: 17898124 PMCID: PMC3575105 DOI: 10.1152/ajpregu.00160.2007] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The contribution of the organum vasculosum laminae terminalis (OVLT) in mediating central hyperosmolality-induced increases of sympathetic nerve activity (SNA) and arterial blood pressure (ABP) was assessed in anesthetized rats. Solutions of graded NaCl concentration (150, 375, and 750 mM) were injected (150 mul) into the forebrain vascular supply via an internal carotid artery (ICA). Time-control experiments (n = 6) established that ICA NaCl injections produced short-latency, transient increases of renal SNA (RSNA) and mean ABP (MAP) (P < 0.05-0.001). Responses were graded, highly reproducible, and unaltered by systemic blockade of vasopressin V1 receptors (n = 4). In subsequent studies, stimulus-triggered averaging of RSNA was used to accurately locate the OVLT. Involvement of OVLT in responses to ICA NaCl was assessed by recording RSNA and MAP responses before and 15 min after electrolytic lesion of the OVLT (n = 6). Before lesion, NaCl injections increased RSNA and MAP (P < 0.05-0.001), similar to time control experiments. After lesion, RSNA responses were significantly reduced (P < 0.05-0.001), but MAP responses were unaltered. To exclude a role for fibers of passage, the inhibitory GABA-A receptor agonist muscimol was microinjected into the OVLT (50 pmol in 50 nl) (n = 6). Before muscimol, hypertonic NaCl increased RSNA, lumbar SNA (LSNA), and MAP (P < 0.05-0.001). After muscimol, both RSNA and LSNA were significantly reduced in response to 375 and 750 mM NaCl (P < 0.05). MAP responses were again unaffected. Injections of vehicle (saline) into OVLT (n = 6) and muscimol lateral to OVLT (n = 5) each failed to alter responses to ICA NaCl. We conclude that OVLT neurons contribute to sympathoexcitation by central hyperosmolality.
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Affiliation(s)
- Peng Shi
- Dept. of Physiology-MC 7756, Univ. of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78229-3900, USA
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