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Mohammed M, Ogunlade B, Elgazzaz M, Berdasco C, Lakkappa N, Ghita I, Guidry JJ, Sriramula S, Xu J, Restivo L, Mendiola Plá MA, Bowles DE, Beyer AM, Yue X, Lazartigues E, Filipeanu CM. Nedd4-2 up-regulation is associated with ACE2 ubiquitination in hypertension. Cardiovasc Res 2023; 119:2130-2141. [PMID: 37161607 PMCID: PMC10478751 DOI: 10.1093/cvr/cvad070] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 03/09/2023] [Accepted: 03/30/2023] [Indexed: 05/11/2023] Open
Abstract
AIMS Angiotensin-converting enzyme 2 (ACE2) is a critical component of the compensatory renin-angiotensin system that is down-regulated during the development of hypertension, possibly via ubiquitination. However, little is known about the mechanisms involved in ACE2 ubiquitination in neurogenic hypertension. This study aimed at identifying ACE2 ubiquitination partners, establishing causal relationships and clinical relevance, and testing a gene therapy strategy to mitigate ACE2 ubiquitination in neurogenic hypertension. METHODS AND RESULTS Bioinformatics and proteomics were combined to identify E3 ubiquitin ligases associated with ACE2 ubiquitination in chronically hypertensive mice. In vitro gain/loss of function experiments assessed ACE2 expression and activity to validate the interaction between ACE2 and the identified E3 ligase. Mutation experiments were further used to generate a ubiquitination-resistant ACE2 mutant (ACE2-5R). Optogenetics, blood pressure telemetry, pharmacological blockade of GABAA receptors in mice expressing ACE2-5R in the bed nucleus of the stria terminalis (BNST), and capillary western analysis were used to assess the role of ACE2 ubiquitination in neurogenic hypertension. Ubiquitination was first validated as leading to ACE2 down-regulation, and Neural precursor cell-expressed developmentally down-regulated protein 4-2 (Nedd4-2) was identified as a E3 ligase up-regulated in hypertension and promoting ACE2 ubiquitination. Mutation of lysine residues in the C-terminal of ACE2 was associated with increased activity and resistance to angiotensin (Ang)-II-mediated degradation. Mice transfected with ACE2-5R in the BNST exhibited enhanced GABAergic input to the paraventricular nucleus (PVN) and a reduction in hypertension. ACE2-5R expression was associated with reduced Nedd4-2 levels in the BNST. CONCLUSION Our data identify Nedd4-2 as the first E3 ubiquitin ligase involved in ACE2 ubiquitination in Ang-II-mediated hypertension. We demonstrate the pivotal role of ACE2 on GABAergic neurons in the maintenance of an inhibitory tone to the PVN and the regulation of pre-sympathetic activity. These findings provide a new working model where Nedd4-2 could contribute to ACE2 ubiquitination, leading to the development of neurogenic hypertension and highlighting potential novel therapeutic strategies.
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Affiliation(s)
- Mazher Mohammed
- Southeast Louisiana Veterans Health Care System, 2400 Canal Street, New Orleans, LA 70119, USA
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
| | - Blessing Ogunlade
- Department of Pharmacology, School of Medicine, Howard University, 520 W St, NW, Washington, DC 20059, USA
| | - Mona Elgazzaz
- Southeast Louisiana Veterans Health Care System, 2400 Canal Street, New Orleans, LA 70119, USA
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
- Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, LA 70112, USA
- Genetics Unit, Department of Histology and Cell Biology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt
| | - Clara Berdasco
- Southeast Louisiana Veterans Health Care System, 2400 Canal Street, New Orleans, LA 70119, USA
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
| | - Navya Lakkappa
- Southeast Louisiana Veterans Health Care System, 2400 Canal Street, New Orleans, LA 70119, USA
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
| | - Ioana Ghita
- Department of Oncology and Diagnostic Sciences, School of Dentistry, University of Maryland, Baltimore, MD 21201, USA
| | - Jessie J Guidry
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
| | - Srinivas Sriramula
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
- Department of Pharmacology and Toxicology, Brody School of Medicine at East Carolina University, Greenville, NC 27834, USA
| | - Jiaxi Xu
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
- Department of Physiology and Pathophysiology, Xi’an Jiaotong University, School of Medicine, Xi’an, 710061, China
| | - Luke Restivo
- Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, LA 70112, USA
| | - Michelle A Mendiola Plá
- Division of Surgical Sciences, Department of Surgery, Duke University, Durham, NC 27710, USA
| | - Dawn E Bowles
- Division of Surgical Sciences, Department of Surgery, Duke University, Durham, NC 27710, USA
| | - Andreas M Beyer
- Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Xinping Yue
- Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, LA 70112, USA
- Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Eric Lazartigues
- Southeast Louisiana Veterans Health Care System, 2400 Canal Street, New Orleans, LA 70119, USA
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University Health Sciences Center, 1900 Perdido Street New Orleans, LA 70112, USA
- Cardiovascular Center of Excellence, Louisiana State University Health Sciences Center, 533 Bolivar Street, New Orleans, LA 70112, USA
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, 2020 Gravier Street, New Orleans LA 70112, USA
| | - Catalin M Filipeanu
- Department of Pharmacology, School of Medicine, Howard University, 520 W St, NW, Washington, DC 20059, USA
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Winter A, Ahlbrand R, Sah R. Recruitment of central angiotensin II type 1 receptor associated neurocircuits in carbon dioxide associated fear. Prog Neuropsychopharmacol Biol Psychiatry 2019; 92:378-386. [PMID: 30776402 DOI: 10.1016/j.pnpbp.2019.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 01/15/2019] [Accepted: 02/14/2019] [Indexed: 11/29/2022]
Abstract
Individuals with fear-associated conditions such as panic disorder (PD) and posttraumatic stress disorder (PTSD) display increased emotional responses to interoceptive triggers, such as CO2 inhalation, that signal a threat to physiological homeostasis. Currently, effector systems and mechanisms underlying homeostatic modulation of fear memory are not well understood. In this regard, the renin angiotensin system (RAS), particularly the angiotensin receptor type 1 (AT1R), a primary homeostatic regulatory target, has gained attention. RAS polymorphisms have been reported in PD and PTSD, and recent studies report AT1R-mediated modulation of fear extinction. However, contribution of AT1Rs in fear evoked by the interoceptive threat of CO2 has not been investigated. Using pharmacological, behavioral, and AT1R/ACE gene transcription analyses, we assessed central AT1R recruitment in CO2-associated fear. CO2 inhalation led to significant AT1R and ACE mRNA upregulation in homeostatic regulatory regions, subfornical organ (SFO) and paraventricular nucleus (PVN), in a temporal manner. Intracerebroventricular infusion of selective AT1R antagonist, losartan, significantly attenuated freezing during CO2 inhalation, and during re-exposure to CO2 context, suggestive of AT1R modulation of contextual fear. Regional Fos mapping in losartan-treated mice post-behavior revealed significantly attenuated labeling in areas regulating defensive behavior, contextual fear, and threat responding; such as, the bed nucleus of stria terminalis, dorsal periaqueductal gray, hypothalamic nuclei, hippocampus, and prefrontal areas such as the prelimbic, infralimbic, and anterior cingulate cortices. Sub-regions of the amygdala did not show CO2-associated AT1R regulation or altered Fos labeling. Collectively, our data suggests central AT1R recruitment in modulation of fear behaviors associated with CO2 inhalation via engagement of neurocircuits regulating homeostasis and defensive behaviors. Our data provides mechanistic insights into the interoceptive regulation of fear, relevant to fear related disorders such as PD and PTSD.
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Affiliation(s)
- Andrew Winter
- Dept. of Pharmacology and Systems Physiology, University of Cincinnati, United States; Neuroscience Graduate Program, University of Cincinnati, United States
| | - Rebecca Ahlbrand
- Dept. of Pharmacology and Systems Physiology, University of Cincinnati, United States; VA Medical Center, Cincinnati, OH, 45221, United States
| | - Renu Sah
- Dept. of Pharmacology and Systems Physiology, University of Cincinnati, United States; Neuroscience Graduate Program, University of Cincinnati, United States; VA Medical Center, Cincinnati, OH, 45221, United States.
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Pleil KE, Helms CM, Sobus JR, Daunais JB, Grant KA, Kash TL. Effects of chronic alcohol consumption on neuronal function in the non-human primate BNST. Addict Biol 2016. [PMID: 26223349 DOI: 10.1111/adb.12289] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Alterations in hypothalamic-pituitary-adrenal axis function contribute to many of the adverse behavioral effects of chronic voluntary alcohol drinking, including alcohol dependence and mood disorders; limbic brain structures such as the bed nucleus of the stria terminalis (BNST) may be key sites for these effects. Here, we measured circulating levels of several steroid hormones and performed whole-cell electrophysiological recordings from acutely prepared BNST slices of male rhesus monkeys allowed to self-administer alcohol for 12 months or a control solution. Initial comparisons revealed that BNST neurons in alcohol-drinking monkeys had decreased membrane resistance, increased frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) with no change in spontaneous excitatory postsynaptic currents (sEPSCs). We then used a combined variable cluster analysis and linear mixed model statistical approach to determine whether specific factors including stress and sex hormones, age and measures of alcohol consumption and intoxication are related to these BNST measures. Modeling results showed that specific measures of alcohol consumption and stress-related hormone levels predicted differences in membrane conductance in BNST neurons. Distinct groups of adrenal stress hormones were negatively associated with the frequency of sIPSCs and sEPSCs, and alcohol drinking measures and basal neuronal membrane properties were additional positive predictors of inhibitory, but not excitatory, PSCs. The amplitude of sEPSCs was highly positively correlated with age, independent of other variables. Together, these results suggest that chronic voluntary alcohol consumption strongly influences limbic function in non-human primates, potentially via interactions with or modulation by other physiological variables, including stress steroid hormones and age.
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Affiliation(s)
- Kristen E. Pleil
- Bowles Center for Alcohol Studies & Department of Pharmacology, School of Medicine; University of North Carolina at Chapel Hill; Chapel Hill NC USA
| | - Christa M. Helms
- Division of Neuroscience, Oregon National Primate Research Center; Oregon Health & Science University; Beaverton OR USA
| | - Jon R. Sobus
- Human Exposure and Atmospheric Sciences Division, National Exposure Research Laboratory, Office of Research and Development; U.S. Environmental Protection Agency; Research Triangle Park NC USA
| | - James B. Daunais
- Department of Physiology & Pharmacology; Wake Forest School of Medicine; Winston-Salem NC USA
| | - Kathleen A. Grant
- Division of Neuroscience, Oregon National Primate Research Center; Oregon Health & Science University; Beaverton OR USA
| | - Thomas L. Kash
- Bowles Center for Alcohol Studies & Department of Pharmacology, School of Medicine; University of North Carolina at Chapel Hill; Chapel Hill NC USA
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Kafami M, Nasimi A. Cardiovascular and single-unit responses to microinjection of angiotensin II into the bed nucleus of the stria terminalis in rat. Neuroscience 2015; 300:418-24. [PMID: 26026681 DOI: 10.1016/j.neuroscience.2015.05.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 05/06/2015] [Accepted: 05/20/2015] [Indexed: 10/23/2022]
Abstract
The bed nucleus of the stria terminalis (BST) is part of the limbic system located in the rostral forebrain. BST is involved in behavioral, neuroendocrine and autonomic functions, including cardiovascular regulation. The angiotensin II (Ang II) receptor, AT1, was found in the BST, however its effects on the cardiovascular system and on single-unit responses have not been studied yet. In the present study, Ang II was microinjected into the BST of anesthetized rats and cardiovascular and single-unit responses were recorded simultaneously. Furthermore the responses were re-tested after the microinjection of a blocker of the AT1 receptor, losartan, into the BST. We found that microinjection of Ang II into the BST produced a pressor response of 11±1mmHg for a duration of 2-8min. Ang II had no consistent effect on heart rate. It also produced two types of single-unit responses in the BST, short excitatory and long inhibitory. Blockade of AT1 receptors abolished both the cardiovascular and single-unit responses, indicating that the responses were mediated through AT1 receptors. These findings imply that Ang II may be utilized as a neurotransmitter and may play a role in returning blood pressure toward normal during hypotension.
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Affiliation(s)
- M Kafami
- Department of Physiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
| | - A Nasimi
- Department of Physiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
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Reporter mouse strain provides a novel look at angiotensin type-2 receptor distribution in the central nervous system. Brain Struct Funct 2014; 221:891-912. [PMID: 25427952 DOI: 10.1007/s00429-014-0943-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 11/07/2014] [Indexed: 02/07/2023]
Abstract
Angiotensin-II acts at its type-1 receptor (AT1R) in the brain to regulate body fluid homeostasis, sympathetic outflow and blood pressure. However, the role of the angiotensin type-2 receptor (AT2R) in the neural control of these processes has received far less attention, largely because of limited ability to effectively localize these receptors at a cellular level in the brain. The present studies combine the use of a bacterial artificial chromosome transgenic AT2R-enhanced green fluorescent protein (eGFP) reporter mouse with recent advances in in situ hybridization (ISH) to circumvent this obstacle. Dual immunohistochemistry (IHC)/ISH studies conducted in AT2R-eGFP reporter mice found that eGFP and AT2R mRNA were highly co-localized within the brain. Qualitative analysis of eGFP immunoreactivity in the brain then revealed localization to neurons within nuclei that regulate blood pressure, metabolism, and fluid balance (e.g., NTS and median preoptic nucleus [MnPO]), as well as limbic and cortical areas known to impact stress responding and mood. Subsequently, dual IHC/ISH studies uncovered the phenotype of specific populations of AT2R-eGFP cells. For example, within the NTS, AT2R-eGFP neurons primarily express glutamic acid decarboxylase-1 (80.3 ± 2.8 %), while a smaller subset express vesicular glutamate transporter-2 (18.2 ± 2.9 %) or AT1R (8.7 ± 1.0 %). No co-localization was observed with tyrosine hydroxylase in the NTS. Although AT2R-eGFP neurons were not observed within the paraventricular nucleus (PVN) of the hypothalamus, eGFP immunoreactivity is localized to efferents terminating in the PVN and within GABAergic neurons surrounding this nucleus. These studies demonstrate that central AT2R are positioned to regulate blood pressure, metabolism, and stress responses.
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Omouessi ST, Falconetti C, Chapleur M, Fernette B, Thornton SN. Mineralocorticoid pretreatment enhances angiotensin II-induced neuronal excitation but not salt drinking in male Fischer rats. J Neuroendocrinol 2007; 19:109-15. [PMID: 17214873 DOI: 10.1111/j.1365-2826.2006.01512.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Central administration of angiotensin (Ang) II stimulates thirst and sodium intake via the AT-1 receptor. Mineralocorticoid pretreatment enhances Ang II-induced drinking of hypertonic salt solutions (i.e. the synergy theory) in Wistar and Sprague-Dawley rats. Electrophysiological experiments using iontophoretic application of Ang II, and the AT-1 receptor specific nonpeptide antagonist losartan, have shown excitation of neurones in the preoptic/medial septum region of urethane anaesthetised male Wistar rats. Deoxycorticosterone acetate (DOCA) pretreatment further enhanced this neuronal excitation to Ang II and reduced the responses to losartan. This generated the hypothesis that DOCA-enhanced Ang II-induced neuronal excitation was necessary for the enhanced salt intake of synergy theory. We tested this hypothesis in Fischer 344 rats that are known to have a low basal salt appetite and reduced sensitivity for i.c.v. Ang II. We compared the effect of DOCA pretreatment on i.c.v. Ang II-induced water and 2% NaCl intake in behaving adult male, Fischer rats, as well as preoptic/medial septum region neuronal responses to Ang II and losartan, using a seven-barrelled micro-iontophoretic electrode sealed to a recording electrode in urethane anaesthetised, male Fischer rats. Two groups were used: one pretreated with DOCA (0.5 mg/day for 3 days) and the other comprising controls, treated with isotonic saline. Ang II applied iontophoretically increased activity in 31% of the spontaneously active neurones. Following DOCA pretreatment, the responsiveness to Ang II (when applied after aldosterone) was increased. By contrast, in the behaving animals, water and 2% NaCl intake in response to i.c.v. Ang II were not enhanced by DOCA pretreatment. These results do not support the working hypothesis but could be interpreted as evidence for the existence of two separately modulated central Ang II systems: one responding to mineralocorticoids with increased neuronal activity and the other responsible for the Ang II-induced sodium appetite in conscious rats.
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Albrecht D, Nitschke T, Von Bohlen Und Halbach O. Various effects of angiotensin II on amygdaloid neuronal activity in normotensive control and hypertensive transgenic [TGR(mREN-2)27] rats. FASEB J 2000; 14:925-31. [PMID: 10783146 DOI: 10.1096/fasebj.14.7.925] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The effects of iontophoretically ejected angiotensin II (Ang II) on the firing rate of neurons in the basolateral complex and the central and cortical amygdala were investigated in two strains of urethane anesthetized rats. In normotensive Sprague-Dawley rats, Ang II induced a significant increase in the discharge rate of responsive amygdaloid neurons. In contrast, in the hypertensive transgenic [TGR(mREN-2)27] rats with higher brain Ang II level, Ang II more often caused inhibitory effects on the amygdaloid firing rate in comparison with controls. The distribution of nonresponsive, excited, and inhibited neurons differed significantly in the two rat strains. Moreover, the responsiveness of amygdaloid neurons was significantly higher in transgenic rats in comparison with controls. Both the increase and the decrease in the firing rate caused by Ang II could be blocked either by angiotensin AT(1) or by AT(2) receptor-specific antagonists. In many cases, the Ang II-induced decrease in the firing rate was antagonized by bicuculline, a gamma-aminobutyric acid (GABA(A)) antagonist. The higher responsiveness of amygdaloid neurons in transgenic rats as well as the predominance of inhibitory effects, presumedly mediated by GABAergic interneurons, could change the output of the amygdala and its influence on thirst, kidney, and cardiovascular function or on processes of learning and anxiety.
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Affiliation(s)
- D Albrecht
- Institute of Physiology, Faculty of Medicine (Charité), Humboldt University, Berlin, Germany.
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von Bohlen und Halbach O, Albrecht D. Opposite effects of angiotensin II and IV in the lateral nucleus of the amygdala. Brain Res Bull 1998; 47:311-5. [PMID: 9886781 DOI: 10.1016/s0361-9230(98)00073-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In this study the effects of angiotensin II and norleucine1-angiotensin IV have been studied in a horizontal in vitro slice preparation of female rat brains. Extracellular field potentials of the lateral nucleus of the basolateral amygdala were recorded. The results show that angiotensin II significantly increased the amplitude of field potentials induced by the electrical stimulation of the lateral nucleus, whereas norleucine1-angiotensin IV caused a significant decrease in the amplitude of field potentials. The angiotensin-induced effects could be blocked by specific angiotensin receptor antagonists. These opposite effects of angiotensin II and IV on electrophysiological parameters are in agreement with behavioral studies that have demonstrated that angiotensin II and IV produce opposite effects on the retention of an inhibitory shock-avoidance response and correlate with their different effects on the blood vessels.
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von Bohlen und Halbach O, Albrecht D. Visualization of specific angiotensin II binding sites in the rat limbic system. Neuropeptides 1998; 32:241-5. [PMID: 10189058 DOI: 10.1016/s0143-4179(98)90043-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The present study examined the distribution of angiotensin-binding cells by using a fluorescence-coupled angiotensin II in fixed horizontal sections that contained several limbic structures. In normal female rats, dense staining was found in the CA3 and CA1 regions and the dentate gyrus of the hippocampus--in the subiculum as well as in the entorhinal cortex and piriform cortex. Moderate staining was found in the CA2 region, in the central and medial nuclei of the amygdala. Low-level staining was obtained in the basolateral and lateral nucleus of the amygdala as well as in the bed nucleus of the stria terminalis. The co-incubation of fluorescence-coupled angiotensin II together with angiotensin II in excess and with saralasin, respectively, suppressed the angiotensin staining in structures investigated.
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Galaverna O, Polidori C, Sakai RR, Liénard F, Chow SY, Fluharty SJ. Blockade of central angiotensin II type 1 and type 2 receptors suppresses adrenalectomy-induced NaCl intake in rats. REGULATORY PEPTIDES 1996; 66:47-50. [PMID: 8899892 DOI: 10.1016/0167-0115(96)00062-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Removal of the adrenal glands, the main site for the synthesis of aldosterone, produces an intake of sodium that is essential for survival. Using central blockade of angiotensin II (Ang II) receptors with SarIle Ang II, previous studies have shown that this intake depends on the stimulation of the brain angiotensin system. In the present study, using intracerebroventricular injection of specific antagonists of Ang II type 1 (AT1) or type 2 (AT2) receptors (losartan and PD 123319, respectively), we confirm that activation of brain angiotensin is essential for the expression of adrenalectomy-induced NaCl intake. Moreover, we show that (a) AT1 but not AT2 receptor blockade alone suppresses NaCl intake and (b) doses of AT1 and AT2 receptor antagonists that separately have no effect on NaCl intake, suppress the behavior when combined. It is proposed that AT1 receptors mediate the natriorexigenic effect of Ang II and that AT2 receptors have a permissive role on AT1 receptor stimulation.
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Affiliation(s)
- O Galaverna
- Department of Animal Physiology, University of Pennsylvania, Philadelphia 19104, USA.
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Liénard F, Thornton SN, Martial FP, Mousseau MC, Nicolaïdis S. Angiotensin II receptor subtype antagonists can both stimulate and inhibit salt appetite in rats. REGULATORY PEPTIDES 1996; 66:87-94. [PMID: 8899899 DOI: 10.1016/0167-0115(96)00061-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In urethane-anaesthetised male Wistar rats iontophoretic application of the angiotensin II (Ang II) type 1 (AT-1) receptor specific nonpeptide antagonist losartan in the septo-preoptic continuum can produce neuronal excitation of short- and long-term duration which has been interpreted as removal of tonic Ang II-induced inhibition. Mineralocorticoid pretreatment, which increases neuronal sensitivity to Ang II to enhance salt appetite, also removes this losartan-induced long-term excitation. These results suggested steroid modulation of the AT-1 receptor and a complex involvement of Ang II in salt appetite. To investigate the role of the inhibitory action of central Ang II on salt appetite, we gave intracerebroventicular injections of a single, low dose (10 ng) of losartan in normal euhydrated rats and this produced, paradoxically, a progressive increase in salt intake (1.6 +/- 0.3 ml/day to 3.5 +/- 0.9 ml/day, n = 15, P < 0.05). Treatment of these salt enhanced rats with DOCA (0.5 mg/day, s.c., for 3 days) further increased the salt appetite, but then a second i.c.v. injection of the same dose of losartan significantly inhibited the enhanced salt appetite (4.7 +/- 0.7 to 1.3 +/- 0.4, n = 9, P < 0.05). These results provide evidence for a complex action of Ang II on the At-1 receptor mediating the generation of salt appetite that appears to involve either at least two functional subtypes of this AT-1 receptor, as already suggested by previous electrophysiological experiments, or one AT-1 receptor with several activation states.
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Affiliation(s)
- F Liénard
- Centre National de la Recherche Scientifique, Collège de France, Paris, France
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