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Hiyama TY. Brain sodium sensing for regulation of thirst, salt appetite, and blood pressure. Physiol Rep 2024; 12:e15970. [PMID: 38479999 PMCID: PMC10937250 DOI: 10.14814/phy2.15970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 02/29/2024] [Indexed: 03/17/2024] Open
Abstract
The brain possesses intricate mechanisms for monitoring sodium (Na) levels in body fluids. During prolonged dehydration, the brain detects variations in body fluids and produces sensations of thirst and aversions to salty tastes. At the core of these processes Nax , the brain's Na sensor, exists. Specialized neural nuclei, namely the subfornical organ (SFO) and organum vasculosum of the lamina terminalis (OVLT), which lack the blood-brain barrier, play pivotal roles. Within the glia enveloping the neurons in these regions, Nax collaborates with Na+ /K+ -ATPase and glycolytic enzymes to drive glycolysis in response to elevated Na levels. Lactate released from these glia cells activates nearby inhibitory neurons. The SFO hosts distinct types of angiotensin II-sensitive neurons encoding thirst and salt appetite, respectively. During dehydration, Nax -activated inhibitory neurons suppress salt-appetite neuron's activity, whereas salt deficiency reduces thirst neuron's activity through cholecystokinin. Prolonged dehydration increases the Na sensitivity of Nax via increased endothelin expression in the SFO. So far, patients with essential hypernatremia have been reported to lose thirst and antidiuretic hormone release due to Nax -targeting autoantibodies. Inflammation in the SFO underlies the symptoms. Furthermore, Nax activation in the OVLT, driven by Na retention, stimulates the sympathetic nervous system via acid-sensing ion channels, contributing to a blood pressure elevation.
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Affiliation(s)
- Takeshi Y. Hiyama
- Department of Integrative PhysiologyTottori University Graduate School and Faculty of MedicineYonagoJapan
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2
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de Melo IS, Sabino-Silva R, Cunha TM, Goulart LR, Reis WL, Jardim ACG, Shetty AK, de Castro OW. Hydroelectrolytic Disorder in COVID-19 patients: Evidence Supporting the Involvement of Subfornical Organ and Paraventricular Nucleus of the Hypothalamus. Neurosci Biobehav Rev 2021; 124:216-223. [PMID: 33577841 PMCID: PMC7872848 DOI: 10.1016/j.neubiorev.2021.02.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 02/07/2023]
Abstract
Multiple neurological problems have been reported in coronavirus disease-2019 (COVID-19) patients because severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) likely spreads to the central nervous system (CNS) via olfactory nerves or through the subarachnoid space along olfactory nerves into the brain's cerebrospinal fluid and then into the brain's interstitial space. We hypothesize that SARS-CoV-2 enters the subfornical organ (SFO) through the above routes and the circulating blood since circumventricular organs (CVOs) such as the SFO lack the blood-brain barrier, and infection of the SFO causes dysfunction of the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON), leading to hydroelectrolytic disorder. SARS-CoV-2 can readily enter SFO-PVN-SON neurons because these neurons express angiotensin-converting enzyme-2 receptors and proteolytic viral activators, which likely leads to neurodegeneration or neuroinflammation in these regions. Considering the pivotal role of SFO-PVN-SON circuitry in modulating hydroelectrolyte balance, SARS-CoV-2 infection in these regions could disrupt the neuroendocrine control of hydromineral homeostasis. This review proposes mechanisms by which SARS-CoV-2 infection of the SFO-PVN-SON pathway leads to hydroelectrolytic disorder in COVID-19 patients.
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Affiliation(s)
- Igor Santana de Melo
- Department of Physiology, Institute of Biological Sciences and Health, Federal University of Alagoas (UFAL), Maceio, Brazil
| | - Robinson Sabino-Silva
- Department of Physiology, Institute of Biomedical Sciences, Federal University of Uberlandia (UFU), Uberlândia, MG, Brazil.
| | - Thúlio Marquez Cunha
- Department of Pulmonology, School of Medicine, Federal University of Uberlandia, Minas Gerais, Brazil
| | - Luiz Ricardo Goulart
- Institute of Biotechnology, Federal University of Uberlandia, Minas Gerais, Brazil
| | - Wagner Luis Reis
- Department of Physiological, Sciences Biological Sciences Centre Federal University of Santa Catarina (UFSC) Florianopolis, Santa Catarina, Brazil
| | - Ana Carolina Gomes Jardim
- Laboratory of Virology, Institute of Biomedical Sciences, Federal University of Uberlandia, Minas Gerais, Brazil
| | - Ashok K Shetty
- Institute for Regenerative Medicine, Department of Molecular and Cellular Medicine, Texas A&M University College of Medicine, College Station, TX, 77843, USA.
| | - Olagide Wagner de Castro
- Department of Physiology, Institute of Biological Sciences and Health, Federal University of Alagoas (UFAL), Maceio, Brazil.
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Black EAE, Smith PM, McIsaac W, Ferguson AV. Brain-derived neurotrophic factor acts at neurons of the subfornical organ to influence cardiovascular function. Physiol Rep 2018; 6:e13704. [PMID: 29802680 PMCID: PMC5974716 DOI: 10.14814/phy2.13704] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 04/17/2018] [Indexed: 11/24/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF), a neurotrophin traditionally associated with neural plasticity, has more recently been implicated in fluid balance and cardiovascular regulation. It is abundantly expressed in both the central nervous system (CNS) and peripheral tissue, and is also found in circulation. Studies suggest that circulating BDNF may influence the CNS through actions at the subfornical organ (SFO), a circumventricular organ (CVO) characterized by the lack of a normal blood-brain barrier (BBB). The SFO, well-known for its involvement in cardiovascular regulation, has been shown to express BDNF mRNA and mRNA for the TrkB receptor at which BDNF preferentially binds. This study was undertaken to determine if: (1) BDNF influences the excitability of SFO neurons in vitro; and (2) the cardiovascular consequences of direct administration of BDNF into the SFO of anesthetized rats. Electrophysiological studies revealed that bath application of BDNF (1 nmol/L) influenced the excitability of the majority of neurons (60%, n = 13/22), the majority of which exhibited a membrane depolarization (13.8 ± 2.5 mV, n = 9) with the remaining affected cells exhibiting hyperpolarizations (-11.1 ± 2.3 mV, n = 4). BDNF microinjections into the SFO of anesthetized rats caused a significant decrease in blood pressure (mean [area under the curve] AUC = -364.4 ± 89.0 mmHg × sec, n = 5) with no effects on heart rate (mean AUC = -12.2 ± 3.4, n = 5). Together these observations suggest the SFO to be a CNS site at which circulating BDNF could exert its effects on cardiovascular regulation.
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Affiliation(s)
- Emily A. E. Black
- Department of Biomedical and Molecular SciencesQueen's UniversityKingstonOntarioCanada
| | - Pauline M. Smith
- Centre for Neuroscience StudiesQueen's UniversityKingstonOntarioCanada
| | - William McIsaac
- Centre for Neuroscience StudiesQueen's UniversityKingstonOntarioCanada
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Plyler KS, Daniels D. Fourth ventricle injection of ghrelin decreases angiotensin II-induced fluid intake and neuronal activation in the paraventricular nucleus of the hypothalamus. Physiol Behav 2017; 178:35-42. [PMID: 27876637 PMCID: PMC5438304 DOI: 10.1016/j.physbeh.2016.11.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/18/2016] [Accepted: 11/18/2016] [Indexed: 02/04/2023]
Abstract
Ghrelin acts in the CNS to decrease fluid intake under a variety of dipsogenic and natriorexigenic conditions. Previous studies on this topic, however, focused on the forebrain as a site of action for this effect of ghrelin. Because the hindbrain contains neural substrates that are capable of mediating the well-established orexigenic effects of ghrelin, the current study tested the hypothesis that ghrelin applied to the hindbrain also would affect fluid intake. To this end, water and saline intakes were stimulated by central injection of angiotensin II (AngII) in rats that also received injections of ghrelin (0.5μg/μl) into either the lateral or fourth ventricle. Ghrelin injected into either ventricle reduced both water and 1.8% NaCl intake that was stimulated by AngII. The nature of the intake effect revealed some differences between the injection sites. For example, forebrain application of ghrelin reduced saline intake by a reduction in both the number of licking bursts and the size of each licking burst, but hindbrain application of ghrelin had a more selective effect on burst number. In an attempt to elucidate a brain structure in which hindbrain-administered ghrelin and forebrain-administered AngII interact to cause the ingestive response, we used Fos-immunohistochemistry in rats given the treatments used in the behavioral experiments. Although several brain areas were found to respond to either ghrelin or AngII, of the sites examined, only the paraventricular nucleus of the hypothalamus (PVN) emerged as a potential site of interaction. Specifically, AngII treatment caused expression of Fos in the PVN that was attenuated by concomitant treatment with ghrelin. These experiments provide the novel finding that the hindbrain contains elements that can respond to ghrelin and cause decreases in AngII-induced fluid intake, and that direct actions by ghrelin on forebrain structures is not necessary. Moreover, these studies suggest that the PVN is an important site of interaction between these two peptides.
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Affiliation(s)
- Kimberly S Plyler
- Behavioral Neuroscience Program, Department of Psychology, The State University of New York at Buffalo, Buffalo, NY 14260, USA
| | - Derek Daniels
- Behavioral Neuroscience Program, Department of Psychology, The State University of New York at Buffalo, Buffalo, NY 14260, USA.
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Hiyama TY, Noda M. Sodium sensing in the subfornical organ and body-fluid homeostasis. Neurosci Res 2016; 113:1-11. [PMID: 27521454 DOI: 10.1016/j.neures.2016.07.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Revised: 07/22/2016] [Accepted: 07/28/2016] [Indexed: 01/28/2023]
Abstract
The brain monitors conditions of body fluids and levels of circulating neuroactive factors to maintain the systemic homeostasis. Unlike most regions in the brain, circumventricular organs (CVOs) lack the blood-brain barrier, and serve as the sensing center. Among the CVOs, the subfornical organ (SFO) is the sensing site of Na+ levels in body fluids to control water and salt intake. The SFO harbors neuronal cell bodies with a variety of hormone receptors and innervates many brain loci. In addition, the SFO harbors specialized glial cells (astrocytes and ependymal cells) expressing Nax, a Na+-level-sensitive sodium channel. These glial cells wrap a specific population of neurons with their processes, and control the firing activities of the neurons by gliotransmitters, such as lactate and epoxyeicosatrienoic acids (EETs), relevant to water/salt-intake behaviors. Recent advances in the understanding of physiological functions of the SFO are reviewed herein with a focus on the Na+-sensing mechanism by Nax.
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Affiliation(s)
- Takeshi Y Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology, and School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Aichi 444-8787, Japan.
| | - Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology, and School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Aichi 444-8787, Japan
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Nation HL, Nicoleau M, Kinsman BJ, Browning KN, Stocker SD. DREADD-induced activation of subfornical organ neurons stimulates thirst and salt appetite. J Neurophysiol 2016; 115:3123-9. [PMID: 27030736 DOI: 10.1152/jn.00149.2016] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 03/25/2016] [Indexed: 01/19/2023] Open
Abstract
The subfornical organ (SFO) plays a pivotal role in body fluid homeostasis through its ability to integrate neurohumoral signals and subsequently alter behavior, neuroendocrine function, and autonomic outflow. The purpose of the present study was to evaluate whether selective activation of SFO neurons using virally mediated expression of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) stimulated thirst and salt appetite. Male C57BL/6 mice (12-15 wk) received an injection of rAAV2-CaMKII-HA-hM3D(Gq)-IRES-mCitrine targeted at the SFO. Two weeks later, acute injection of clozapine N-oxide (CNO) produced dose-dependent increases in water intake of mice with DREADD expression in the SFO. CNO also stimulated the ingestion of 0.3 M NaCl. Acute injection of CNO significantly increased the number of Fos-positive nuclei in the SFO of mice with robust DREADD expression. Furthermore, in vivo single-unit recordings demonstrate that CNO significantly increases the discharge frequency of both ANG II- and NaCl-responsive neurons. In vitro current-clamp recordings confirm that bath application of CNO produces a significant membrane depolarization and increase in action potential frequency. In a final set of experiments, chronic administration of CNO approximately doubled 24-h water intake without an effect on salt appetite. These findings demonstrate that DREADD-induced activation of SFO neurons stimulates thirst and that DREADDs are a useful tool to acutely or chronically manipulate neuronal circuits influencing body fluid homeostasis.
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Affiliation(s)
- Haley L Nation
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
| | - Marvin Nicoleau
- Department of Biochemistry and Molecular Biology, Franklin & Marshall College, Lancaster, Pennsylvania
| | - Brian J Kinsman
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
| | - Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
| | - Sean D Stocker
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania; and
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Mecawi AS, Vilhena-Franco T, Araujo IG, Reis LC, Elias LLK, Antunes-Rodrigues J. Estradiol potentiates hypothalamic vasopressin and oxytocin neuron activation and hormonal secretion induced by hypovolemic shock. Am J Physiol Regul Integr Comp Physiol 2011; 301:R905-15. [PMID: 21632848 DOI: 10.1152/ajpregu.00800.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Estrogen receptors are located in important brain areas that integrate cardiovascular and hydroelectrolytic responses, including the subfornical organ (SFO) and supraoptic (SON) and paraventricular (PVN) nuclei. The aim of this study was to evaluate the influence of estradiol on cardiovascular and neuroendocrine changes induced by hemorrhagic shock in ovariectomized rats. Female Wistar rats (220-280 g) were ovariectomized and treated for 7 days with vehicle or estradiol cypionate (EC, 10 or 40 μg/kg, sc). On the 8th day, animals were subjected to hemorrhage (1.5 ml/100 g for 1 min). Hemorrhage induced acute hypotension and bradycardia in the ovariectomized-oil group, but EC treatment inhibited these responses. We observed increases in plasma angiotensin II concentrations and decreases in plasma atrial natriuretic peptide levels after hemorrhage; EC treatment produced no effects on these responses. There were also increases in plasma vasopressin (AVP), oxytocin (OT), and prolactin levels after the induction of hemorrhage in all groups, and these responses were potentiated by EC administration. SFO neurons and parvocellular and magnocellular AVP and OT neurons in the PVN and SON were activated by hemorrhagic shock. EC treatment enhanced the activation of SFO neurons and AVP and OT magnocellular neurons in the PVN and SON and AVP neurons in the medial parvocellular region of the PVN. These results suggest that estradiol modulates the cardiovascular responses induced by hemorrhage, and this effect is likely mediated by an enhancement of AVP and OT neuron activity in the SON and PVN.
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Affiliation(s)
- Andre S Mecawi
- Faculty of Medicine of Ribeirao Preto, Department of Physiology, University of Sao Paulo, Sao Paulo, Brazil
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Hashimoto H, Otsubo H, Fujihara H, Suzuki H, Ohbuchi T, Yokoyama T, Takei Y, Ueta Y. Centrally administered ghrelin potently inhibits water intake induced by angiotensin II and hypovolemia in rats. J Physiol Sci 2010; 60:19-25. [PMID: 19760484 PMCID: PMC10717457 DOI: 10.1007/s12576-009-0062-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 08/25/2009] [Indexed: 10/20/2022]
Abstract
Ghrelin is a potent, centrally acting orexigenic hormone. Recently, we showed that centrally administered ghrelin is a potent antidipsogenic hormone in 24-h water deprived rats. In this study, we examined the effect of intracerebroventricular (icv) injection of ghrelin on angiotensin II (AII)-induced water intake in rats. We also examined the effects of icv injection of ghrelin on drinking induced by intraperitoneal injection of an isotonic polyethylene glycol (PEG) solution that causes isotonic hypovolemia. Water intake induced by the icv injection of AII or ip injection of PEG was significantly reduced after icv injection of ghrelin, although food intake was stimulated by the hormone. The drinking induced by AII was also inhibited by the icv administration of 4alpha-phorbol 12, 13-didecanoate, an agonist of the osmosensitive TRPV4 channel. This study showed that ghrelin is a potent antidipsogenic peptide by antagonizing general dipsogenic mechanisms including those activated by AII and hypovolemia in rats.
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Affiliation(s)
- Hirofumi Hashimoto
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555 Japan
| | - Hiroki Otsubo
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555 Japan
| | - Hiroaki Fujihara
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555 Japan
| | - Hitoshi Suzuki
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555 Japan
| | - Toyoaki Ohbuchi
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555 Japan
| | - Toru Yokoyama
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555 Japan
| | - Yoshio Takei
- Laboratory of Physiology, Department of Marine Bioscience, Ocean Research Institute, University of Tokyo, Tokyo, 164-8639 Japan
| | - Yoichi Ueta
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu, 807-8555 Japan
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Hindmarch C, Fry M, Yao ST, Smith PM, Murphy D, Ferguson AV. Microarray analysis of the transcriptome of the subfornical organ in the rat: regulation by fluid and food deprivation. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1914-20. [DOI: 10.1152/ajpregu.90560.2008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have employed microarray technology using Affymetrix 230 2.0 genome chips to initially catalog the transcriptome of the subfornical organ (SFO) under control conditions and to also evaluate the changes (common and differential) in gene expression induced by the challenges of fluid and food deprivation. We have identified a total of 17,293 genes tagged as present in one of our three experimental conditions, transcripts, which were then used as the basis for further filtering and statistical analysis. In total, the expression of 46 genes was changed in the SFO following dehydration compared with control animals (22 upregulated and 24 downregulated), with the largest change being the greater than fivefold increase in brain-derived neurotrophic factor (BDNF) expression, while significant changes in the expression of the calcium-sensing (upregulated) and apelin (downregulated) receptors were also reported. In contrast, food deprivation caused greater than twofold changes in a total of 687 transcripts (222 upregulated and 465 downregulated), including significant reductions in vasopressin, oxytocin, promelanin concentrating hormone, cocaine amphetamine-related transcript (CART), and the endothelin type B receptor, as well as increases in the expression of the GABAB receptor. Of these regulated transcripts, we identified 37 that are commonly regulated by fasting and dehydration, nine that were uniquely regulated by dehydration, and 650 that are uniquely regulated by fasting. We also found five transcripts that were differentially regulated by fasting and dehydration including BDNF and CART. In these studies we have for the first time described the transcriptome of the rat SFO and have in addition identified genes, the expression of which is significantly modified by either water or food deprivation.
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Cottrell GT, Ferguson AV. Sensory circumventricular organs: central roles in integrated autonomic regulation. ACTA ACUST UNITED AC 2004; 117:11-23. [PMID: 14687696 DOI: 10.1016/j.regpep.2003.09.004] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Circumventricular organs (CVO) play a critical role as transducers of information between the blood, neurons and the cerebral spinal fluid (CSF). They permit both the release and sensing of hormones without disrupting the blood-brain barrier (BBB) and as a consequence of such abilities the CVOs are now well established to have essential regulatory actions in diverse physiological functions. The sensory CVOs are essential signal transducers located at the blood-brain interface regulating autonomic function. They have a proven role in the control of cardiovascular function and body fluid regulation, and have significant involvement in central immune response, feeding behavior and reproduction, the extent of which is still to be determined. This review will attempt to summarize the research on these topics to date. The complexities associated with sensory CVO exploration are intense, but should continue to result in valuable contributions to our understanding of brain function.
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Affiliation(s)
- G Trevor Cottrell
- Department of Physiology, Queen's University, Botterell Hall, 4th Floor, Kingston, ON, Canada K7L 3N6
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LaGrange LP, Toney GM, Bishop VS. Effect of intravenous angiotensin II infusion on responses to hypothalamic PVN injection of bicuculline. Hypertension 2003; 42:1124-9. [PMID: 14597646 PMCID: PMC3567845 DOI: 10.1161/01.hyp.0000102181.83892.04] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The hypothalamic paraventricular nucleus (PVN) plays an important role in the sympathoexcitatory response to elevated plasma angiotensin II (Ang II). However, the mechanism by which Ang II influences sympathetic activity is not fully understood. In this study, we tested the hypothesis that GABA(gamma-aminobutyric acid)-ergic function in the PVN is reduced by peripheral infusion of Ang II. To accomplish this, rats received either intravenous Ang II (12 ng/kg per minute) or vehicle (D5W) for 7 days, and renal sympathetic nerve activity (SNA), mean arterial pressure (MAP), and heart rate (HR) responses were recorded after unilateral PVN microinjection of the GABA-A receptor antagonist bicuculline methiodide (BMI, 0.1 nmol). Results indicate that in contrast to a significant increase in renal SNA, MAP, and HR observed in vehicle-infused rats (P<0.05), BMI injection into the PVN of Ang II-infused animals was without effect on all recorded variables. In a separate groups of animals, ganglionic blockade produced a significantly greater fall in MAP (P<0.01) in Ang II-infused rats than in vehicle-infused control rats, indicating that the contribution of SNA to the maintenance of blood pressure was elevated in the Ang II-infused group. Overall, these data indicate that cardiovascular and sympathoexcitatory responses to acute GABA-A receptor antagonism in the PVN are significantly blunted in rats after 7 days of intravenous infusion of Ang II. We conclude that an Ang II-induced reduction in GABAergic inhibition within the PVN may contribute to elevated SNA observed in this study.
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Affiliation(s)
- Lila P LaGrange
- Department of Physiology-7756, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Tex 78229-3900, USA.
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LaGrange LP, Toney GM, Bishop VS. Chronic angiotensin II infusion attenuates the renal sympathoinhibitory response to acute volume expansion. Am J Physiol Regul Integr Comp Physiol 2003; 284:R1098-107. [PMID: 12626370 PMCID: PMC3564518 DOI: 10.1152/ajpregu.00165.2002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study the hypothesis was tested that chronic infusion of ANG II attenuates acute volume expansion (VE)-induced inhibition of renal sympathetic nerve activity (SNA). Rats received intravenous infusion of either vehicle or ANG II (12 ng. kg(-1). min(-1)) for 7 days. ANG II-infused animals displayed an increased contribution of SNA to the maintenance of mean arterial pressure (MAP) as indicated by ganglionic blockade, which produced a significantly (P < 0.01) greater decrease in MAP (75 +/- 3 mmHg) than was observed in vehicle-infused (47 +/- 8 mmHg) controls. Rats were then anesthetized, and changes in MAP, mean right atrial pressure (MRAP), heart rate (HR), and renal SNA were recorded in response to right atrial infusion of isotonic saline (20% estimated blood volume in 5 min). Baseline MAP, HR, and hematocrit were not different between groups. Likewise, MAP was unchanged by acute VE in vehicle-infused animals, whereas VE induced a significant bradycardia (P < 0.05) and increase in MRAP (P < 0.05). MAP, MRAP, and HR responses to VE were not statistically different between animals infused with vehicle vs. ANG II. In contrast, VE significantly (P < 0.001) reduced renal SNA by 33.5 +/- 8% in vehicle-infused animals but was without effect on renal SNA in those infused chronically with ANG II. Acutely administered losartan (3 mg/kg iv) restored VE-induced inhibition of renal SNA (P < 0.001) in rats chronically infused with ANG II. In contrast, this treatment had no effect in the vehicle-infused group. Therefore, it appears that chronic infusion of ANG II can attenuate VE-induced renal sympathoinhibition through a mechanism requiring AT(1) receptor activation. The attenuated sympathoinhibitory response to VE in ANG II-infused animals remained after arterial barodenervation and systemic vasopressin V(1) receptor antagonism and appeared to depend on ANG II being chronically increased because ANG II given acutely had no effect on VE-induced renal sympathoinhibition.
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Affiliation(s)
- Lila P LaGrange
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA
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Tanaka J, Miyakubo H, Fujisawa S, Nomura M. Reduced dipsogenic response induced by angiotensin II activation of subfornical organ projections to the median preoptic nucleus in estrogen-treated rats. Exp Neurol 2003; 179:83-9. [PMID: 12504870 DOI: 10.1006/exnr.2002.8054] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study was carried out to investigate whether estrogen modulates the drinking response induced by activation of angiotensinergic neural pathways from the subfornical organ (SFO) to the median preoptic nucleus (MnPO). Microinjection of angiotensin II (ANG II, 10(-10) M, 0.2 microl) into the SFO elicited drinking in ovariectomized (OVX) female rats that were treated with either propylene glycol (PG) vehicle or estrogen benzoate (EB). The amount of water intake induced by the ANG II injection was significantly greater in the PG-treated than in the EB-treated animals. In both groups of female rats, previous injections of saralasin (Sar, 10(-10) M, 0.2 microl), a specific ANG II antagonist, into the MnPO resulted in the significant attenuation of the drinking response to ANG II, showing that the ANG II-induced drinking response may be mediated in part by the angiotensinergic SFO projections to the MnPO. Injections of ANG II (10(-10) M, 0.2 microl) into the MnPO caused drinking in both groups, while no significant difference was found between the groups in the amount of water intake. These results suggest that increases in the circulating level of estrogen may attenuate the drinking response induced by ANG II activation of the SFO projections to the MnPO.
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Affiliation(s)
- Junichi Tanaka
- Department of Curriculum, Teaching and Memory, Neuroscience Program, Naruto University of Education, Naruto, Tokushima 772-8502, Japan
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Tanaka J, Mashiko N, Kawakami A, Ushigome A, Nomura M. GABAergic systems in the nucleus tractus solitarius regulate noradrenaline release in the subfornical organ area in the rat. Auton Neurosci 2002; 100:58-65. [PMID: 12422961 DOI: 10.1016/s1566-0702(02)00152-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Previous studies have shown that catecholaminergic neurons in the nucleus tractus solitarius (NTS) with ascending projections to the subfornical organ (SFO) are highly sensitive to gamma-aminobutyric acid (GABA). To clarify the role of the GABAergic system in the NTS in the regulation of the activity of noradrenergic NTS projections to the SFO, the present study was carried out to investigate the effects of local administration (50 nl) of GABA, the GABA(A) agonist muscimol, the GABA(B) agonist baclofen, the GABA(A) antagonist bicuculline or the GABA(B) antagonist phaclofen into the NTS on the release of noradrenaline (NA) in the region of the SFO using microdialysis techniques in rats under urethane anesthesia. Microinjections of GABA (10(-4) - 10(-2) M) into the region of the NTS significantly decreased the NA release in the SFO area. Injections of either muscimol (10(-4) - 10(-2) M) or baclofen (10(-5) - 10(-3) M) into the NTS region significantly attenuated the NA release in the SFO area. Injections of bicuculline (10(-5) and 10(-4) M), but not phaclophen (10(-6) - 10(-4) M), into the NTS region significantly enhanced the NA release in the SFO area, suggesting that the GABAergic system in the NTS may tonically inhibit the NA release in the SFO area through a GABA(A) receptor mechanism. Neither injection of these drugs in any of the doses used in this study into the NTS region caused any significant changes in the NA release in the sites away from the SFO. Injections of vehicle (50 nl) into the NTS region had no significant effect on the NA release in either the SFO area or the sites away from the SFO. These results suggest that the GABAergic system in the NTS may serve to decrease the release of NA in the SFO area and the two types of GABA receptors are involved in the modulation of the NA release.
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Affiliation(s)
- Junichi Tanaka
- Neuroscience Program, Teaching and Memory, Naruto University of Education, Tokushima, Japan.
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15
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Miyakubo H, Hayashi Y, Tanaka J. Enhanced response of subfornical organ neurons projecting to the hypothalamic paraventricular nucleus to angiotensin II in spontaneously hypertensive rats. Auton Neurosci 2002; 95:131-6. [PMID: 11871778 DOI: 10.1016/s1566-0702(01)00388-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Thirty subfornical organ (SFO) neurons in normotensive Wistar-Kyoto (WKY) rats and 32 SFO neurons in spontaneously hypertensive rats (SHR) were antidromically activated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN) under urethane anesthesia. The spontaneous firing rate was significantly higher in SHR than in WKY rats. No significant differences in the latency, conduction velocity, and threshold of antidromic response were observed between WKY and SHR. All the identified SFO units were tested for a response to intracarotid injection of angiotensin II (ANG II, 20-ng/kg b.w.t.). Injections of ANG II elicited an increase in the activity of 21 units in WKY and 20 units in SHR and a depression in the firing of one unit in WKY rats, but did not affect the remaining units. The magnitude of the excitatory response caused by the ANG II injection was much greater in SHR than in WKY rats. These results show that there are differences between WKY and SHR in the spontaneous discharge rate of SFO neurons projecting to the PVN and in their response to circulating ANG II.
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Affiliation(s)
- Hiroko Miyakubo
- Department of Human Development, Naruto University of Education, Tokushima, Japan
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16
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Warren JH, Lewis W, Wraa CE, Stebbins CL. Central and peripheral effects of angiotensin II on the cardiovascular response to exercise. J Cardiovasc Pharmacol 2001; 38:693-705. [PMID: 11602816 DOI: 10.1097/00005344-200111000-00006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The authors tested the hypothesis that angiotensin II modulates cardiovascular responses to dynamic exercise via peripheral and central effects on the autonomic nervous system. Ten subjects performed three identical exercise tests during treatment with placebo, valsartan (an angiotensin II type 1 receptor blocker), or enalapril (an angiotensin-converting enzyme inhibitor). With placebo, plasma concentrations of angiotensin II, norepinephrine, and epinephrine were elevated during cycling at 80% of heart rate reserve (HRR). Enalapril attenuated increases in heart rate, mean arterial pressure (MAP), and catecholamines during cycling, whereas valsartan only attenuated MAP and rate-pressure product above 60% HRR, and norepinephrine. The different responses provoked by the two drug treatments suggest that angiotensin-converting enzyme inhibition affects cardiovascular responses to exercise by mechanisms unrelated to production of angiotensin II. Indices of autonomic function during dynamic exercise were not changed by either drug. Attenuation of norepinephrine release during exercise by valsartan suggests that angiotensin II facilitates the release of norepinephrine from sympathetic postganglionic neurons. Angiotensin II, therefore, contributes to the pressor response to exercise by inducing peripheral vasoconstriction and facilitation of norepinephrine release from postganglionic sympathetic nerve endings that are unrelated to central activation of the autonomic nervous system.
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Affiliation(s)
- J H Warren
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, Davis, California 95616-8634, USA
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17
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Tanaka J, Miyakubo H, Nomura M. Estrogen decreases the responsiveness of subfornical organ neurons to angiotensinergic neural inputs from the lateral hypothalamic area in the female rat. Exp Neurol 2001; 171:301-7. [PMID: 11573982 DOI: 10.1006/exnr.2001.7743] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Twenty-eight subfornical organ (SFO) neurons in ovariectomized (OVX) female rats that were treated with propylene glycol (PG) vehicle and 26 SFO neurons in OVX female rats that were treated with estrogen benzoate (EB) were antidromically activated by electrical stimulation of the hypothalamic paraventricular nucleus (PVN) under urethane anesthesia. No significant differences were observed between the PG-treated and EB-treated OVX animals in the latency, conduction velocity, or threshold of antidromic activation. The mean spontaneous discharge rate was significantly lower in the EB-treated than in the PG-treated OVX animals. In both groups, the activity of the majority (86% in the PG-treated animals and 88% in the EB-treated animals) of identified SFO neurons were activated by microiontophoretic application of angiotensin II (ANG II). Electrical stimulation of the lateral hypothalamic area (LHA) increased the excitability of these ANG II-sensitive SFO neurons (58% in the PG-treated animals and 52% in the EB-treated animals). The excitatory response to either ANG II or LHA stimulation was blocked by microiontophoretic application of the ANG II antagonist saralasin (Sar), suggesting that the excitatory response to LHA stimulation may be mediated by angiotensinergic LHA projections to the SFO. The magnitude of excitatory response to either ANG II or the LHA stimulation was much greater in the PG-treated than in the EB-treated animals. These results suggest that estrogen decreases the responsiveness of SFO neurons projecting to the PVN to angiotensinergic inputs from the LHA.
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Affiliation(s)
- J Tanaka
- Department of Human Development, Naruto University of Education, Naruto, Tokushima, 772-8502, Japan.
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Tanaka J, Miyakubo H, Okumura T, Sakamaki K, Hayashi Y. Estrogen decreases the responsiveness of subfornical organ neurons projecting to the hypothalamic paraventricular nucleus to angiotensin II in female rats. Neurosci Lett 2001; 307:155-8. [PMID: 11438387 DOI: 10.1016/s0304-3940(01)01940-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Extracellular single-unit activity was recorded from subfornical organ (SFO) neurons antidromically identified as projecting to the hypothalamic paraventricular nucleus (PVN) in urethane-anesthetized ovariectomized female rats that were treated with either propylene glycol (PG) vehicle or estradiol benzoate (EB). No significant differences were observed between the PG- and EB-treated rats in the latency, conduction velocity, or threshold of antidromic activation. The mean spontaneous firing rate was significantly lower and the refractory period was significantly longer in the EB-treated rats. In the identified units that were activated by angiotensin II (ANG II) applied iontophoretically, the amount of excitatory response to intracarotid administration of ANG II was much greater in the PG-treated than in the EB-treated rats. These results suggest that estrogen may decrease the responsiveness of SFO neurons projecting to the PVN to circulating ANG II.
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Affiliation(s)
- J Tanaka
- Department of Human Development, Naruto University of Education, Takashima, Naruto-cho, Naruto, 772-8502, Tokushima, Japan.
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19
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Fujisawa S, Tanaka J, Nomura M. Estrogen attenuates the drinking response induced by activation of angiotensinergic pathways from the lateral hypothalamic area to the subfornical organ in female rats. Behav Brain Res 2001; 122:33-41. [PMID: 11287074 DOI: 10.1016/s0166-4328(01)00176-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The present study was carried out to investigate whether estrogen modulates the drinking response induced by activation of angiotensinergic neural pathways from the lateral hypothalamic area (LHA) to the subfornical organ (SFO) in the female rats. Microinjection of ANG II (10(-10) M, 0.2 microl) into the LHA caused drinking in 17 out of 26 ovariectomized (OVX) female rats that were treated with propylene glycol (PG) vehicle and in 18 out of 28 OVX female rats that were treated with estrogen benzoate (EB). In both groups, previous injections of the ANG II antagonist saralasin (Sar, 10(-10) M, 0.2 microl) into the SFO significantly attenuated the water intake caused by the ANG II injection, suggesting that the ANG II-induced drinking response may be mediated by the angiotensinergic LHA projections to the SFO. Injections of ANG II (10(-10) M, 0.2 microl) into the SFO elicited drinking in all the animals that demonstrated the drinking response to ANG II injected into the LHA. The amount of water intake caused by either the injection of ANG II into the LHA or the SFO was significantly greater in the PG-treated than in the EB-treated animals. These results suggest that the circulating estrogen may act to attenuate the dipsogenic response induced by activation of the angiotensinergic pathways from the LHA to the SFO.
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Affiliation(s)
- S Fujisawa
- Department of Physiology, Saitama Medical School, Iruma-gun, 350-0495, Saitama, Japan
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20
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Tanaka J, Okumura T, Sakamaki K, Miyakubo H. Activation of serotonergic pathways from the midbrain raphe system to the subfornical organ by hemorrhage in the rat. Exp Neurol 2001; 169:156-62. [PMID: 11312568 DOI: 10.1006/exnr.2000.7611] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of serotonergic neural pathways from the midbrain raphe nuclei to the subfornical organ (SFO) in the central regulation of cardiovascular function and body fluid balance was investigated in adult male rats under urethane anesthesia. Eleven neurons in the dorsal raphe nucleus (DR) were antidromically activated by electrical stimulation of the SFO. Of these neurons, 6 displayed an excitatory response following hemorrhage (10 ml/kg bwt) while the remaining 5 neurons were unresponsive. Ninety-four neurons in the SFO were tested for a response to electrical stimulation of the DR or hemorrhage. Electrical stimulation of the DR caused orthodromic excitation (19%) or inhibition (5%) of the activity of SFO neurons. In 14 of 18 SFO neurons that displayed the excitation to the stimulation of the DR, hemorrhage (30 to 50 mm Hg suppression in mean arterial pressure) produced an increase of their discharge, while the stimulus was without effect in the remaining neurons responsive to the stimulation of the DR. The effects of hemorrhage on serotonin (5-HT) release in the region of the SFO were examined using intracerebral microdialysis techniques. Hemorrhage significantly increased 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the region of the SFO. The present data suggest that the serotonergic pathways from the DR to the SFO may relay activation of the peripheral baroreceptors to SFO neurons which result in enhanced excitability, indicating the involvement of the pathways in the regulation of cardiovascular function.
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Affiliation(s)
- J Tanaka
- Department of Human Development, Naruto University of Education, Tokushima, Takashima, Naruto, 772-8502, Japan
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21
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Tanaka J, Hayashi Y, Sakamaki K, Okumura T, Nomura M. Activation of the subfornical organ enhances extracellular noradrenaline concentrations in the hypothalamic paraventricular nucleus in the rat. Brain Res Bull 2001; 54:421-5. [PMID: 11306195 DOI: 10.1016/s0361-9230(01)00425-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Experiments were carried out to investigate whether angiotensinergic efferent pathways from the subfornical organ (SFO) regulate the noradrenergic system in the region of the hypothalamic paraventricular nucleus (PVN). Intracerebral microdialysis techniques were utilized to quantify the extracellular content of noradrenaline (NA) in the PVN area. In urethane-anaesthetized male rats, electrical stimulation (5-20 Hz, 600 microA) of the SFO significantly increased the NA concentration in the region of the PVN, and the increase was significantly prevented by pretreatment with the angiotensin II (ANG II) antagonist saralasin (Sar, 5 microg), into the third ventricle (3V). Injections of ANG II (5 microg) into the 3V significantly enhanced NA release in the PVN area. These results suggest that the angiotensinergic pathways from the SFO to the PVN may act to enhance NA release in the region of the PVN.
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Affiliation(s)
- J Tanaka
- Department of Human Development, Naruto University of Education, Takashima, Naruto-cho, Naruto, Tokushima, Japan.
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22
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Ferguson AV, Washburn DL, Latchford KJ. Hormonal and neurotransmitter roles for angiotensin in the regulation of central autonomic function. Exp Biol Med (Maywood) 2001; 226:85-96. [PMID: 11446443 DOI: 10.1177/153537020122600205] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In this review we present the case for both hormonal and neurotransmitter actions of angiotensin II (ANG) in the control of neuronal excitability in a simple neural pathway involved in central autonomic regulation. We will present both single-cell and whole-animal data highlighting hormonal roles for ANG in controlling the excitability of subfornical organ (SFO) neurons. More controversially we will also present the case for a neurotransmitter role for ANG in SFO neurons in controlling the excitability of identified neurons in the paraventricular nucleus (PVN) of the hypothalamus. In this review we highlight the similarities between the actions of ANG on these two populations of neurons in an attempt to emphasize that whether we call such actions "hormonal" or "neurotransmitter" is largely semantic. In fact such definitions only refer to the method of delivery of the chemical messenger, in this case ANG, to its cellular site of action, in this case the AT1 receptor. We also described in this review some novel concepts that may underlie synthesis, metabolic processing, and co-transmitter actions of ANG in this pathway. We hope that such suggestions may lead ultimately to the development of broader guiding principles to enhance our understanding of the multiplicity of physiological uses for single chemical messengers.
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Affiliation(s)
- A V Ferguson
- Department of Physiology, Queen's University, Kingston, Ontario, Canada.
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23
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Tanaka J, Hayashi Y, Nomura S, Miyakubo H, Okumura T, Sakamaki K. Angiotensinergic and noradrenergic mechanisms in the hypothalamic paraventricular nucleus participate in the drinking response induced by activation of the subfornical organ in rats. Behav Brain Res 2001; 118:117-22. [PMID: 11164509 DOI: 10.1016/s0166-4328(00)00320-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The present study was done to investigate the contribution of the hypothalamic paraventricular nucleus (PVN) to the drinking response caused by activation of the subfornical organ (SFO) following angiotensin II (ANG II) injections in the awake rat. Microinjection of ANG II into the SFO elicited the drinking response. Previous injections of either saralasin, an ANG II antagonist, or phentolamine, an alpha-adrenoceptor antagonist, bilaterally into the PVN resulted in the significant attenuation of the drinking response to ANG II. Similar injections of any of the beta-adrenoceptor antagonist timolol, the muscarinic antagonist atropine, or saline vehicle into the PVN had no significant effect on the drinking response. In an attempt to clarify the neural mechanisms in the PVN involved in the drinking response to ANG II injected into the SFO, the effect of microinjection of ANG II into the SFO on noradrenaline (NA) release in the PVN was examined using intracerebral microdialysis techniques. The injection of the ANG II, but not saline vehicle, significantly enhanced the NA release in the region of the PVN. These results indicate the involvement of both the angiotensinergic and alpha-adrenergic systems in the PVN in the drinking response caused by angiotensinergic activation of the SFO, and imply that the angiotensinergic projections from the SFO to the PVN may serve to increase NA release which results in mediating water intake.
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Affiliation(s)
- J Tanaka
- Department of Human Development, Naruto University of Education, Takashima, Naruto-cho, Naruto, Tokushima 772-8502, Japan.
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24
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25
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Tanaka J, Hayashi Y, Watai T, Hori K, Nomura M. Noradrenaline release in the rat subfornical organ area to blood pressure changes. Exp Neurol 1998; 152:303-6. [PMID: 9710529 DOI: 10.1006/exnr.1998.6841] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To verify whether noradrenergic inputs to the subfornical organ (SFO) are involved in the control system of arterial pressure, we investigated the effects of blood pressure changes on noradrealine (NA) release in the SFO and its surrounding sites using microdialysis techniques in rats. Hemorrhage (5 or 10 ml/kg) significantly increased the NA concentration in the region of the SFO, but did not cause significant changes in the sites away from the SFO. An elevation in arterial pressure following intravenous administration of the alpha-agonist metaraminol slightly decreased the NA level in the region of the SFO. These results imply that the noradrenergic neural inputs to the SFO area may be involved in the control of cardiovascular function.
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Affiliation(s)
- J Tanaka
- Department of Human Development, Department of Education for Handicapped Children, Naruto University of Education, Takashima, Naruto, Tokushima, 772-8502, Japan
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26
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Tanaka J, Hayashi Y, Shimamune S, Nomura M. Ascending pathways from the nucleus of the solitary tract to the subfornical organ in the rat. Brain Res 1997; 777:237-41. [PMID: 9449435 DOI: 10.1016/s0006-8993(97)01211-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Electrical stimulation of the nucleus of the solitary tract (NTS) produced orthodromic excitation (n = 28, 15%) and inhibition (n = 6, 4%) of the activity of neurons in the subfornical organ (SFO) in male rats under urethane anesthesia. Almost all (n = 26) of the excitatory responses (n = 28) were blocked by microiontophoretically applied phentolamine, an alpha-adrenergic antagonist, but not by timolol, a beta-adrenergic antagonist. In contrast, the inhibitory response of all the neurons (n = 6) tested was not affected by either phentolamine or timolol. Approximately two-third (n = 19) of SFO neurons that demonstrated the excitatory response to NTS stimulation exhibited an increase in neuronal activity in response to hemorrhage (10 ml/kg b.w.t.). Hemorrhage did not cause any change in the activity of all the neurons that demonstrated the inhibitory response to NTS stimulation. These results suggest that the excitatory pathways from the NTS to the SFO may transmit the peripheral baroreceptor information through alpha-adrenoreceptor mechanisms.
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Affiliation(s)
- J Tanaka
- Department of Human Development, Naruto University of Education, Tokushima, Japan
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27
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Ferguson AV, Bains JS. Actions of angiotensin in the subfornical organ and area postrema: implications for long term control of autonomic output. Clin Exp Pharmacol Physiol 1997; 24:96-101. [PMID: 9043813 DOI: 10.1111/j.1440-1681.1997.tb01790.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
1. Considerable physiological and anatomical evidence indicates that circulating angiotensin II (AngII), plays important roles in the long-term regulation of autonomic output as a result of actions in two circumventricular structures, the subfornical organ (SFO) and area postrema (AP). 2. Extracellular recordings have demonstrated excitatory actions of AngII on neurons from both of these structures which are AT1 receptor mediated, maintained when cells are placed in synaptic isolation, and are dose dependent. Interestingly SFO neurons appear to be an order of magnitude more sensitive to AngII than those in AP. 3. Recent calcium imaging studies have demonstrated that AngII induces increases in intracellular calcium in both SFO and AP neurons. Whole cell patch recordings have also begun to provide important information suggesting that AngII actions may modulate voltage activated ion channels in these two structures to elicit its observed actions on circumventricular organs (CVO) neurons at the blood-brain interface. 4. Through these actions circulating AngII is thus able to influence efferent projections from these CVO which in turn influence the output of hypothalamic cells projecting to the posterior pituitary (vasopressin secretion), nucleus tractus solitarius (NTS), and intermediolateral cell column of the spinal cord (to influence sympathetic preganglionics), and medullary neurons in the NTS.
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Affiliation(s)
- A V Ferguson
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
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28
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Chiodera P, Volpi R, Capretti L, Caiazza A, Marchesi M, Caffari G, Rossi G, Coiro V. Oxytocin response to challenging stimuli in elderly men. REGULATORY PEPTIDES 1994; 51:169-76. [PMID: 8059013 DOI: 10.1016/0167-0115(94)90206-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The present study was carried out in order to establish possible alterations in oxytocin (OT) secretion with aging. Therefore, we evaluated the OT responses to insulin (0.15 U/kg)-induced hypoglycemia or to the administration of angiotensin II (i.v. infusion for 60 min of successively increasing doses of 4, 8 and 16 ng/kg min; each dose for 20 min) or apomorphine (60 micrograms/kg s.c.) in male subjects aged 22-80 yr and divided into 3 groups by age (group I (n = 9): 22-38 yr; group II (n = 9): 41-60 yr; group III (n = 9): 63-80 yr). Basal OT concentrations were similar in all groups. The OT response during the insulin tolerance test and the administration of ANG II had similar patterns and magnitudes in all groups. The OT response to apomorphine was similar in the two younger groups, with plasma OT levels increased 118% vs. baseline. In contrast, apomorphine was unable to induce a significant OT rise in the oldest group. During apomorphine test plasma OT concentrations were significantly lower in group III than in groups I and II. For the first time in elderly human subjects, these data show normal responsiveness of the OT secretory system to releasing stimuli such as hypoglycemia and ANG II. These findings indicate that in aged men production of OT and capability of responding to challenging stimuli is unchanged. On the other hand, the reduced OT responsiveness to apomorphine in group III might be an expression of the general dopaminergic dysfunction affecting the aging brain.
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Affiliation(s)
- P Chiodera
- Department of Internal Medicine, University of Parma, Italy
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29
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Yang CC, Chan JY, Pan JT, Chan SH. Differential neuronal responses to angiotensin III from the subfornical organ of normotensive and spontaneously hypertensive rats. Brain Res 1994; 638:169-74. [PMID: 8199857 DOI: 10.1016/0006-8993(94)90646-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We previously reported that chronic central administration of angiotensin III (AIII) fails to produce sustained drinking behavior in spontaneously hypertensive rats (SHR), possibly because of the development of early desensitization of the angiotensin receptors. The present study extended these findings to the cellular level, using brain-slice preparation from Wistar-Kyoto rats (WKY) and SHR, in conjunction with single-neuron recording in the subfornical organ (SFO), a target site for angiotensin II-induced drinking. We found that a majority of the SFO neurons studied (13/18 in WKY, 20/28 in SHR) responded in a dose-related manner to AIII, given in the range of 10(-6)-10(-5) M. This excitation was receptor-specific, since it was reversed by Ile7-AIII (10(-4)-10(-3) M), the selective AIII antagonist. Bestatin (10(-5)-10(-4) M), an aminopeptidase B inhibitor, did not discernibly affect basal spike frequency when delivered alone. Nevertheless, given in combination with the heptapeptide, bestatin reduced the intensity and duration of SFO neuronal response in WKY to the higher dose (10(-5) M), and in SHR to both doses (10(-6) or 10(-5) M), of AIII. These data suggest that the SFO may also be a central site of action for AIII. Moreover, prolonging the action of AIII by protecting it from being metabolized with bestatin may produce desensitization of the angiotensin receptors on SFO neurons. This was particularly so in the SHR, which are thought to be defective in the degradation of the heptapeptide in the brain.
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Affiliation(s)
- C C Yang
- Institute of Pharmacology, National Yang-Ming Medical College, Taipei, Taiwan, ROC
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30
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Rowland NE, Li BH, Rozelle AK, Fregly MJ, Garcia M, Smith GC. Localization of changes in immediate early genes in brain in relation to hydromineral balance: intravenous angiotensin II. Brain Res Bull 1994; 33:427-36. [PMID: 8124581 DOI: 10.1016/0361-9230(94)90286-0] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Immediate early genes, detected by Fos- and Jun-like immunoreactivity (FLI, JLI), were induced in discrete regions of the rat brain by intravenous infusion of angiotensin II (Ang II) at dipsogenic doses. The regions included subfornical organ (SFO), organum vasculosum laminae terminalis (OVLT), median preoptic nucleus (MnPO), supraoptic nucleus (SON), and the magnocellular part of the paraventricular hypothalamus (PVH). These responses were sustained for up to 6 h of infusion. In SFO, FLI was induced preferentially in the posterior part, while JLI occurred in more central regions. Cerebroventricular (ICV) injection of the Ang II type 1 receptor (AT-1) antagonist, losartan potassium, completely prevented the FLI induced by Ang II in these brain regions. ICV injection of the Ang II type 2 receptor (AT-2) antagonist, PD 123319, did not reduce Ang II-induced FLI in SFO, OVLT and MnPO, but markedly attenuated the activation in SON and PVH. To determine whether SFO is the primary site for transduction of the circulating Ang II signal, electrolytic lesions were made in or rostral to the SFO. Rats with complete lesions showed a complete absence of Ang-induced FLI in SON and PVH. The data are discussed in terms of functional mapping of the brain regions activated by circulating Ang II and neural circuitry for water intake, including the possible role of AT-2 receptors in PVH and SON.
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Affiliation(s)
- N E Rowland
- Department of Psychology, University of Florida, Gainesville 32611-2065
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López Avalos MD, Mancera JM, Pérez-Fígares JM, Fernández-Llebrez P. Immunocytochemical localization of corticotropin-releasing factor in the brain of the turtle, Mauremys caspica. ANATOMY AND EMBRYOLOGY 1993; 188:163-71. [PMID: 8214631 DOI: 10.1007/bf00186250] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Brain sections of the turtle, Mauremys caspica were studied by means of an antiserum against rat corticotropin-releasing factor. Immunoreactive neurons were identified in telencephalic, diencephalic and mesencephalic areas such as the cortex, nucleus caudatus, nucleus accumbens, amygdala, subfornical organ, paraventricular nucleus, hypothalamic dorsolateral aggregation, nucleus of the paraventricular organ, infundibular nucleus, pretectal nucleus, periventricular grey, reticular formation and nucleus of the raphe. Many immunoreactive cells located near the ependyma were bipolar, having an apical dendrite that contacted the cerebrospinal fluid. Immunoreactive fibers were seen in these locations and in the lamina terminalis, lateral forebrain bundle, supraoptic nucleus, median eminence, neurohypophysis, tectum opticum, torus semicircularis and deep mesencephalic nucleus. Parvocellular bipolar immunoreactive neurons from the paraventricular and infundibular nuclei projected axons that joined the hypothalamo-hypophysial tract and reached the outer zone of median eminence, and the neural lobe of the hypophysis where immunoreactive fibers terminated close to intermediate lobe cells. From these results it can be concluded that, as in other vertebrates, corticotropin-releasing factor in the turtle may act as a releasing factor and, centrally, as a neurotransmitter or neuromodulator.
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Affiliation(s)
- M D López Avalos
- Departamento de Biología Celular, Facultad de Ciencias, Universidad de Málaga, Spain
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Tanaka J, Nojima K, Yamamuro Y, Saito H, Nomura M. Responses of subfornical organ neurons projecting to the hypothalamic paraventricular nucleus to hemorrhage. Brain Res 1993; 608:141-4. [PMID: 8495337 DOI: 10.1016/0006-8993(93)90785-l] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The activity of subfornical organ (SFO) neurons that were antidromically identified by electrical stimulation of the rat hypothalamic paraventricular nucleus (PVN) was tested for a response to microiontophoretic application of angiotensin II (ANG II) or hemorrhage (10 ml/kg b.w.t.). Microiontophoretically (MIPh) applied ANG II caused an increased excitability in 24 out of 28 neurons tested and the excitation was blocked by MIPh-applied saralasin (Sar), a specific ANG II antagonist. Of these neurons that responded to ANG II, 14 displayed an increase in neuronal firing in response to hemorrhage, while 10 were unresponsive. The excitatory response to hemorrhage in 5 out of 14 neurons tested was prevented by MIPh-applied Sar, whereas the response of the remaining neurons was not affected. These results show that part of SFO neurons projecting to the PVN may receive neural inputs from the peripheral baroreceptors, and suggest that the inputs may be partially attributable to the involvement of central angiotensinergic circuits.
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Affiliation(s)
- J Tanaka
- Department of Physiology, Saitama Medical School, Japan
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33
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Wright JW, Roberts KA, Stubley LA, Hanesworth JM, Harding JW. Hypothalamic angiotensin release in response to AII or glutamic acid stimulation of the SFO in rats. Brain Res Bull 1993; 31:649-54. [PMID: 8100178 DOI: 10.1016/0361-9230(93)90136-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Recent evidence from our laboratory suggests that angiotensin II (AII) is synthesized, stored within cells in the paraventricular nucleus (PVN) of the hypothalamus, and upon appropriate stimulation, released and rapidly converted to angiotensin III (AIII). The present investigation extends these observations by first employing a retrograde tracer to confirm a direct connection from the subfornical organ (SFO) to the PVN, and then showing that microinfusion of AII or glutamic acid into the SFO provokes release of endogenous angiotensin within the PVN. Potentially it is this release that contributes to the elevations in blood pressure and drinking that have been reported to occur with electrical and chemical stimulation of the SFO. These results represent the first evidence of releasable angiotensin provoked by the chemical activation of a neural pathway that has been histochemically demonstrated to link the SFO with the PVN and brain stem structures concerned with cardiovascular functioning.
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Affiliation(s)
- J W Wright
- Department of Psychology, Washington State University, Pullman 99164
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34
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Wright JW, Harding JW. Regulatory role of brain angiotensins in the control of physiological and behavioral responses. ACTA ACUST UNITED AC 1992; 17:227-62. [PMID: 1361394 DOI: 10.1016/0165-0173(92)90018-h] [Citation(s) in RCA: 226] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Considerable evidence now indicates that a separate and distinct renin-angiotensin system (RAS) is present within the brain. The necessary precursors and enzymes required for the formation and degradation of the biologically active forms of angiotensins have been identified in brain tissues as have angiotensin binding sites. Although this brain RAS appears to be regulated independently from the peripheral RAS, circulating angiotensins do exert a portion of their actions via stimulation of brain angiotensin receptors located in circumventricular organs. These circumventricular organs are located in the proximity of brain ventricles, are richly vascularized and possess a reduced blood-brain barrier thus permitting accessibility by peptides. In this way the brain RAS interacts with other neurotransmitter and neuromodulator systems and contributes to the regulation of blood pressure, body fluid homeostasis, cyclicity of reproductive hormones and sexual behavior, and perhaps plays a role in other functions such as memory acquisition and recall, sensory acuity including pain perception and exploratory behavior. An overactive brain RAS has been identified as one of the factors contributing to the pathogenesis and maintenance of hypertension in the spontaneously hypertensive rat (SHR) model of human essential hypertension. Oral treatment with angiotensin-converting enzyme inhibitors, which interfere with the formation of angiotensin II, prevents the development of hypertension in young SHR by acting, at least in part, upon the brain RAS. Delivery of converting enzyme inhibitors or specific angiotensin receptor antagonists into the brain significantly reduces blood pressure in adult SHR. Thus, if the SHR is an appropriate model of human essential hypertension (there is controversy concerning its usefulness), the potential contribution of the brain RAS to this dysfunction must be considered during the development of future antihypertensive compounds.
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Affiliation(s)
- J W Wright
- Department of Psychology, Washington State University, Pullman 99164-4820
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35
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Abstract
Endothelin (ET), a potent vasoconstrictor peptide, is believed to have central sites of action and potential neurohormonal effects relating to body fluid homeostasis and blood-pressure regulation. Systemic endothelin binds to receptors at circumventricular organs and has been shown to increase plasma concentrations of vasopressin and increase the firing frequency of neurohypophysial vasopressin and oxytocin neurons. In the present study we have examined the effects of ET on blood-pressure following micro-injection into the subfornical organ (SFO). Micro-injection of 0.5 and 5.0 pmol of endothelin into SFO caused significant increases (10.1 +/- 1.1 and 10.2 +/- 2.1, respectively) in blood pressure, while lower doses were without effect. In addition, we have used single unit recording techniques to evaluate the effects of systemic ET on the activity of SFO neurons. Extracellular recordings from SFO neurons, antidromically identified as projecting to PVN, showed predominantly excitatory responses to systemic ET (21/35 cells). The data demonstrate that ET has excitatory actions on SFO neurons, and further raise the possibility that one of the functional consequences of such effects is an increase in arterial blood pressure.
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Affiliation(s)
- K M Wall
- Department of Physiology, Queen's University, Kingston, Ont., Canada
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36
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Palkovits M, Bahner U, Geiger H, Fodor M, Lenkei Z, Heidland A. Atrial natriuretic factor in the subfornical organ and the organum vasculosum laminae terminalis. PROGRESS IN BRAIN RESEARCH 1992; 91:251-9. [PMID: 1410409 DOI: 10.1016/s0079-6123(08)62341-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- M Palkovits
- Laboratory of Neuromorphology, Semmelweis University Medical School, Budapest, Hungary
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37
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Ferguson AV. Neurophysiological analysis of mechanisms for subfornical organ and area postrema involvement in autonomic control. PROGRESS IN BRAIN RESEARCH 1992; 91:413-21. [PMID: 1410428 DOI: 10.1016/s0079-6123(08)62361-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- A V Ferguson
- Department of Physiology, Queen's University, Kingston, Ont., Canada
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38
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Russell JA, Douglas AJ, Bull PM, Pumford KM, Bicknell RJ, Leng G. Pregnancy and opioid interactions with the anterior perithird ventricular input to magnocellular oxytocin neurones. PROGRESS IN BRAIN RESEARCH 1992; 91:41-53. [PMID: 1410427 DOI: 10.1016/s0079-6123(08)62314-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J A Russell
- Department of Physiology, University Medical School, Edinburgh, U.K
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39
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Terrell ML, Kadekaro M, Freeman S, Eisenberg H. Effects of chemical stimulation of the subfornical organ on metabolic activity of the hypothalamo-neurohypophysial system in rats. Neurosci Lett 1991; 134:122-6. [PMID: 1815144 DOI: 10.1016/0304-3940(91)90522-u] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Topical stimulation of the subfornical organ (SFO) with angiotensin II (ANG II) or acetylcholine (ACh) increased blood pressure, water intake, and the activity of the hypothalamo-neurohypophysial system (HNS). The pressor and drinking responses were higher and the metabolic activity of the HNS, measured with the [14C]deoxyglucose (DG) method, was lower with ANG-II than with ACh. Glucose utilization in the neural lobe increased by 165% with ACh as opposed to 65% with ANG II. These results demonstrate the ANG II and ACh mobilize differentially the mechanisms increasing blood pressure, drinking responses, and the activity of the HNS.
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Affiliation(s)
- M L Terrell
- Division of Neurosurgery, University of Texas Medical Branch, Galveston 77550
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40
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Oldfield BJ, Hards DK, McKinley MJ. Projections from the subfornical organ to the supraoptic nucleus in the rat: ultrastructural identification of an interposed synapse in the median preoptic nucleus using a combination of neuronal tracers. Brain Res 1991; 558:13-9. [PMID: 1657310 DOI: 10.1016/0006-8993(91)90708-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The subfornical organ, along with other regions of the lamina terminalis, may contain osmoreceptors and is likely to be a site of action of blood-borne angiotensin II. The neural pathways by which these stimuli lead to vasopressin secretion, have been suggested to extend from the subfornical organ to hypothalamic sites of vasopressin production either directly or via synapses in an intervening nucleus such as the median preoptic nucleus. In the present study, cholera toxin conjugated to horseradish peroxidase (CT/HRP) or colloidal gold (CT/Au) has been injected, respectively, into the subfornical organ and supraoptic nucleus of the same animal. The anterograde and retrograde transport of the toxin from these two sites has made possible the identification, at the ultrastructural level, of a synapse in the median preoptic nucleus interposed in the pathway between the subfornical organ and the supraoptic nucleus. Moreover, the presence of retrogradely transported CT/HRP and CT/Au in the same neurone in the median preoptic nucleus indicates that some neurones in this nucleus have axons with collateral branches to both the subfornical organ and supraoptic nucleus. Either or both of these pathways may transmit information related to the tonicity of the blood or circulating levels of angiotensin II to sites in the hypothalamus.
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Affiliation(s)
- B J Oldfield
- Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Vic., Australia
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41
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Robinzon B, Ben-David A, Koike TI, Kinzler SL, Neldon HL. Effect of intrahypothalamic injections of norepinephrine and serotonin on plasma arginine vasotocin and mesotocin in the White Leghorn cockerel. Br Poult Sci 1991; 32:597-606. [PMID: 1893269 DOI: 10.1080/00071669108417385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1. Saline (10 microliters), norepinephrine (NE) and Serotonin (5-HT), 500 nmol each, were injected into the anterior third ventricle (A3V; n = 7) or the posterior third ventricle (P3V; n = 11) of ananesthetised, unrestrained White Leghorn cockerels. Plasma arginine vasotocin (AVT) and mesotocin (MT) were measured 20, 60 and 120 min after injection. 2. Injection of NE into both the A3V and P3V had no significant effect on either plasma AVT or plasma MT at any of the sampling times. 3. Administration of 5-HT into the A3V significantly increased plasma MT about two-fold 20 min following injection. At 120 min time, plasma MT returned to normal. 4. In P3V birds, 5-HT had no effect on plasma MT in the first 20 min, but a significant increase in plasma MT occurred 60 to 120 min after injection. The magnitude of the response was lower than in the A3V cockerels. 5. Plasma AVT was not affected by 5-HT administration into the A3V at any of the sampling times, but 5-HT administration into the P3V caused significant rises in plasma AVT at 120 min. 6. Serotonergic, but not noradrenergic, induction of neurohypophysial peptide secretion was demonstrated.
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Affiliation(s)
- B Robinzon
- Department of Animal Science, Faculty of Agriculture, Hebrew University of Jerusalem, Rehavot, Israel
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42
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Mancera JM, López Avalos MD, Pérez-Fígares JM, Fernández-Llebrez P. The distribution of corticotropin-releasing factor--immunoreactive neurons and nerve fibers in the brain of the snake, Natrix maura. Coexistence with arginine vasotocin and mesotocin. Cell Tissue Res 1991; 264:539-48. [PMID: 1868522 DOI: 10.1007/bf00319043] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The anatomical distribution of neurons and nerve fibers containing corticotropin-releasing factor (CRF) has been studied in the brain of the snake, Natrix maura, by means of immunocytochemistry using an antiserum against rat CRF. To test the possible coexistence of CRF with the neurohypophysial peptides arginine vasotocin (AVT) and mesotocin (MST) adjacent sections were stained with antisera against the two latter peptides. CRF-immunoreactive (CRF-IR) neurons exist in the paraventricular nucleus (PVN). In some neurons of the PVN, coexistence of CRF with MST or of CRF with AVT has been shown. Numerous CRF-IR fibers run along the hypothalamo-hypophysial tract and end in the outer layer of the median eminence. In addition, some fibers reach the neural lobe of the hypophysis. CRF-IR perikarya have also been identified in the following locations: dorsal cortex, nucleus accumbens, amygdala, subfornical organ, lamina terminalis, nucleus of the paraventricular organ, nucleus of the oculomotor nerve, nucleus of the trigeminal nerve, and reticular formation. In addition to all these locations CRF-IR fibers were also observed in the lateral septum, supraoptic nucleus, habenula, lateral forebrain bundle, paraventricular organ, hypothalamic ventromedial nucleus, raphe and interpeduncular nuclei.
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Affiliation(s)
- J M Mancera
- Departamento de Biología Celular, Facultad de Ciencias, Málaga, España
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43
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Castañeyra-Perdomo A, Perez-Delgado MM, Meyer G, Carmona-Calero E, Perez-Gonzalez H, Gonzalez-Hernandez T, Ferres-Torres R. Alcohol effects on the morphometric development of the subfornical organ and area postrema of the albino mouse. Alcohol 1991; 8:65-70. [PMID: 2006987 DOI: 10.1016/0741-8329(91)91280-f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have studied the development of the nuclear sizes of ependymocytes and neurons of two circumventricular organs of the male alcoholic mouse: the Subfornical Organ (SFO) and the Area Postrema (AP), comparing the results with a control group. The global volume of both centers was also studied. The results show that the SFO, a structure related to the control of fluid balance, responds to alcoholism with an increase of the global volume. This increase could be related to the variations of salt-water balance and/or blood pressure in chronic alcoholism. However, the size of cell nuclei in the SFO is not affected. In contrast, the AP responds to chronic alcoholism like other nervous centres, with a decrease of the nuclear size of its cells. The global volume of AP does not change.
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Affiliation(s)
- A Castañeyra-Perdomo
- Departamento de Anatomia, Facultad de Medicina, Universidad de La Laguna, Tenerife, Spain
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44
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Mendelsohn FA, Allen AM, Chai SY, McKinley MJ, Oldfield BJ, Paxinos G. The brain angiotensin system: insights from mapping its components. Trends Endocrinol Metab 1990; 1:189-98. [PMID: 18411117 DOI: 10.1016/1043-2760(90)90052-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mapping of components of the angiotensin (Ang) system in the brain suggests that it serves multiple central roles, including regulation of fluid and electrolyte balance, central autonomic control, and pituitary hormone release.
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Affiliation(s)
- F A Mendelsohn
- Department of Medicine, University of Melbourne, Austin Hospital, Victoria, Australia
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45
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Hatton GI. Emerging concepts of structure-function dynamics in adult brain: the hypothalamo-neurohypophysial system. Prog Neurobiol 1990; 34:437-504. [PMID: 2202017 DOI: 10.1016/0301-0082(90)90017-b] [Citation(s) in RCA: 371] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
As the first known of the mammalian brain's neuropeptide systems, the magnocellular hypothalamo-neurohypophysial system has become a model. A great deal is known about the stimulus conditions that activate or inactivate the elements of this system, as well as about many of the actions of its peptidergic outputs upon peripheral tissues. The well-characterized actions of two of its products, oxytocin and vasopressin, on mammary, uterine, kidney and vascular tissues have facilitated the integration of newly discovered, often initially puzzling, information into the existing body of knowledge of this important regulatory system. At the same time, new conceptions of the ways in which neuropeptidergic neurons, or groups of neurons, participate in information flow have emerged from studies of the hypothalamo-neurohypophysial system. Early views of the SON and PVN nuclei, the neurons of which make up approximately one-half of this system, did not even associate these interesting, darkly staining anterior hypothalamic cells with hormone secretion from the posterior pituitary. Secretion from this part of the pituitary, it was thought, was neurally evoked from the pituicytes that made the oxytocic and antidiuretic "principles" and then released them upon command. When these views were dispelled by the demonstration that the hormones released from the posterior pituitary were synthesized in the interesting cells of the hypothalamus, the era of mammalian central neural peptidergic systems was born. Progress in developing an ever more complete structural and functional picture of this system has been closely tied to advancements in technology, specifically in the areas of radioimmunoassay, immunocytochemistry, anatomical tracing methods at the light and electron microscopic levels, and sophisticated preparations for electrophysiological investigation. Through the judicious use of these techniques, much has been learned that has led to revision of the earlier held views of this system. In a larger context, much has been learned that is likely to be of general application in understanding the fundamental processes and principles by which the mammalian nervous system works.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- G I Hatton
- Neuroscience Program, Michigan State University, East Lansing 48824-1117
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46
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Donevan SD, Van Vugt DA, Ferguson AV. Subfornical organ activation stimulates luteinizing hormone secretion in the rat. Brain Res 1989; 488:398-402. [PMID: 2743137 DOI: 10.1016/0006-8993(89)90738-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effect of electrical stimulation in the subfornical organ (SFO) on plasma luteinizing hormone (LH) concentrations has been examined in the conscious freely moving male Sprague-Dawley rat. Plasma LH levels were significantly elevated above basal levels 15 min following stimulation in the SFO. In contrast, stimulation in the adjacent hippocampal commissure caused no significant change in plasma concentrations of LH. These results correlate well with previous electrophysiological studies demonstrating that SFO stimulation activates putative LH-releasing hormone (LH-RH) containing neurons in the septum which project to the median eminence and add further support to the hypothesis that the SFO plays a significant role in the control of reproductive function.
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Affiliation(s)
- S D Donevan
- Department of Physiology, Queen's University, Kingston, Ont., Canada
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47
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Shioya M, Tanaka J. Inputs from the nucleus of the solitary tract to subfornical organ neurons projecting to the paraventricular nucleus in the rat. Brain Res 1989; 483:192-5. [PMID: 2706508 DOI: 10.1016/0006-8993(89)90054-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Extracellular single-unit activity was recorded from 26 subfornical organ (SFO) neurons antidromically identified as projecting to the hypothalamic paraventricular nucleus (PVN) in urethane-anesthetized male rats. Of these identified SFO neurons, 10 displayed an inhibitory response and 2 exhibited an excitatory response in neuronal excitability following electrical stimulation of the nucleus of the solitary tract (NTS), while the remaining neurons were unresponsive. Eight out of 10 SFO neurons that demonstrated the inhibitory response to NTS stimulation also displayed a reduction in ongoing activity in response to activation of peripheral baroreceptors, achieved by rising arterial blood pressure with an intravenous administration of the alpha-agonist metaraminol, whereas the remaining responsive neurons to NTS stimulation were ineffective. These results show that a part of SFO neurons projecting to the PVN may receive inhibitory inputs from the peripheral baroreceptors through NTS neurons.
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Affiliation(s)
- M Shioya
- Department of Animal Science, College of Agriculture and Veterinary Medicine, Nihon University, Kanagawa, Japan
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48
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Leng G, Blackburn RE, Dyball RE, Russell JA. Role of anterior peri-third ventricular structures in the regulation of supraoptic neuronal activity and neurohypophysical hormone secretion in the rat. J Neuroendocrinol 1989; 1:35-46. [PMID: 19210480 DOI: 10.1111/j.1365-2826.1989.tb00074.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Abstract Neurohypophysical hormone release, and the electrical activity of single neurons of the supraoptic nucleus, were monitored in urethane-anaesthetized rats. Immediately after electrolytic lesions of the region anterior and ventral to the third ventricle (AV3V region), supraoptic neurons showed little spontaneous activity and their responses to ip injection of hypertonic saline were severely impaired; corresponding deficits were found in the secretion of both oxytocin and vasopressin. Similar deficits in oxytocin secretion were also found in rats following electrolytic lesions which destroyed all or part of the subfornical organ; however the effects of the lesions were not additive: rats with lesions of both the AV3V region and the subfornical organ region showed a similar degree of impairment of osmotically stimulated oxytocin secretion to rats with lesions of either site alone. Such deficits might occur either as a result of destruction of osmoresponsive projections to the magnocellular nuclei, or as a result of destruction of an afferent input which is essential for the full expression of the innate osmosensitivity of supraoptic neurons. To test the latter possibility, supraoptic neurons in AV3V-lesioned rats were activated by continuous application of glutamate, and then tested with ip injection of hypertonic saline. Five of seven cells tested responded significantly to the hyperosmotic stimulus, though the responses were significantly weaker than observed in sham-lesioned rats. We suggest that the innate osmosensitivity of supraoptic neurons does contribute to their responses to systemic osmotic stimulation, but that expression of this innate osmosensitivity requires inputs from the AV3V region and/or the subfornical organ, some of which may also be osmoresponsive. Electrical stimulus pulses applied to the AV3V region influenced the electrical activity of most supraoptic neurons strongly: the predominant response was a short-latency, short-duration inhibition followed by long-latency, long-duration excitation. Whereas intracerebroventricular administration of the angiotensin II antagonist saralasin reduced spontaneous or osmotically induced activity of supraoptic neurons, the neuronal responses to AV3V stimulation were impaired only with relatively high doses of saralasin. We conclude that angiotensin ll-sensitive neurons are an important component of the afferent pathways that sustain the excitability of supraoptic neurons, but that angiotensin is probably not the major transmitter of the projection from the AV3V region to the supraoptic nucleus.
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Affiliation(s)
- G Leng
- AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge CB2 4AT, UK
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49
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Castrén E, Saavedra JM. Angiotensin II receptors in paraventricular nucleus, subfornical organ, and pituitary gland of hypophysectomized, adrenalectomized, and vasopressin-deficient rats. Proc Natl Acad Sci U S A 1989; 86:725-9. [PMID: 2911602 PMCID: PMC286547 DOI: 10.1073/pnas.86.2.725] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Angiotensin II has been implicated in the regulation of adrenocorticotropin and vasopressin secretion. Angiotensin II may influence the secretion of these hormones either directly at the pituitary gland or by increasing corticotropin-releasing hormone or vasopressin release from cells that are located in the paraventricular hypothalamic nucleus. Pituitary hormone release may also be influenced by circulating angiotensin II through receptors outside the blood-brain barrier in the subfornical organ. We have used alterations in angiotensin II receptors in hypophysectomized, adrenalectomized, and vasopressin-deficient Brattleboro rats as indicators of the activity of angiotensin II in the regulation of adrenocorticotropin and vasopressin secretion. Angiotensin receptor number in the paraventricular nucleus and the subfornical organ, but not in the anterior pituitary gland, was significantly decreased by adrenalectomy, and this effect was reversed by corticoids. Vasopressin deficiency decreased angiotensin receptors in the subfornical organ and increased them in the anterior pituitary gland but did not affect angiotensin II binding in either magnocellular or parvocellular subnucleus of the paraventricular nucleus. Our results suggest that angiotensin II may have a corticoid-dependent role in the regulation of corticotropin-releasing hormone secretion, which could be important in the adaptation to elevated corticosterone secretion in stress.
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Affiliation(s)
- E Castrén
- Unit of Preclinical Neuropharmacology, National Institute of Mental Health, Bethesda, MD 20892
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Ferguson AV, Kasting NW. Angiotensin acts at the subfornical organ to increase plasma oxytocin concentrations in the rat. REGULATORY PEPTIDES 1988; 23:343-52. [PMID: 3238055 DOI: 10.1016/0167-0115(88)90235-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We have examined the effects of systemic angiotensin II (AII) on plasma oxytocin (OXY) concentrations in freely moving male Sprague-Dawley rats. We have also examined the role of the subfornical organ (SFO) as a CNS site at which circulating AII acts to influence secretion of this neurohypophysial peptide. OXY concentrations were measured by radioimmunoassay in plasma samples obtained by drawing blood samples through indwelling atrial catheters. In SFO intact animals (n = 8) AII infusion (1.0 microgram/kg/min) resulted in increases in plasma OXY concentrations from baseline values of 6.8 +/- 2.5 pg/ml to postinfusion concentrations of 44.9 +/- 11.9 pg/ml. In a second series of experiments electrolytic lesions were placed in the region of the SFO prior to testing the effects of AII infusion on OXY concentrations. Two further experimental groups were thus established according to the histologically verified location of lesions in either the rostral or caudal SFO. In the caudal SFO lesioned group AII infusion resulted in increases in plasma OXY concentrations from control values of 6.9 +/- 1.4 pg/ml to postinfusion levels of 45.1 +/- 9.8 pg/ml. These changes were not significantly different from the SFO intact group. In contrast rostral SFO lesions resulted in significantly elevated basal concentrations of OXY (17.4 +/- 3.4 pg/ml, n = 6) while postinfusion concentrations were found to be 22.8 +/- 4.9 pg/ml indicating that AII infusion was without effect following such lesions. These data are in accordance with the hypothesis that circulating AII acts at the SFO to influence SFO efferents which in turn activate OXY secreting neurons in the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei. These neuroendocrine cells then release this peptide into the systemic circulation from the posterior pituitary.
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Affiliation(s)
- A V Ferguson
- Department of Physiology, Queen's University, Kingston, Ont., Canada
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