1
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Nasimi A, Haddad F, Mirzaei-Damabi N, Rostami B, Hatam M. Another controller system for arterial pressure. AngII-vasopressin neural network of the parvocellular paraventricular nucleus may regulate arterial pressure during hypotension. Brain Res 2021; 1769:147618. [PMID: 34400123 DOI: 10.1016/j.brainres.2021.147618] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 08/05/2021] [Accepted: 08/09/2021] [Indexed: 02/07/2023]
Abstract
Angiotensin II (AngII) immunoreactive cells, fibers and receptors, were found in the parvocelluar region of paraventricular nucleus (PVNp) and AngII receptors are present on vasopressinergic neurons. However, the mechanism by which vasopressin (AVP) and AngII may interact to regulate arterial pressure is not known. Thus, we tested the cardiovascular effects of blockade of the AngII receptors on AVP neurons and blockade of vasopressin V1a receptors on AngII neurons. We also explored whether the PVNp vasopressin plays a regulatory role during hypotension in anesthetized rat or not. Hypovolemic-hypotension was induced by gradual bleeding from femoral venous catheter. Either AngII or AVP injected into the PVNp produced pressor and tachycardia responses. The responses to AngII were blocked by V1a receptor antagonist. The responses to AVP were partially attenuated by AT1 antagonist and greatly attenuated by AT2 antagonist. Hemorrhage augmented the pressor response to AVP, indicating that during hemorrhage, sensitivity of PVNp to vasopressin was increased. By hemorrhagic-hypotension and bilateral blockade of V1a receptors of the PVNp, we found that vasopressinergic neurons of the PVNp regulate arterial pressure towards normal during hypotension. Taken together these findings and our previous findings about angII (Khanmoradi and Nasimi, 2017a) for the first time, we found that a mutual cooperative system of angiotensinergic and vasopressinergic neurons in the PVNp is a major regulatory controller of the cardiovascular system during hypotension.
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Affiliation(s)
- Ali Nasimi
- Dept. of Physiology, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Fatemeh Haddad
- Dept. of Physiology, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Nafiseh Mirzaei-Damabi
- Dept. of Physiology, Shiraz University of Medical Sciences, Shiraz, Iran; Epilepsy Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Bahar Rostami
- Dept. of Physiology, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Masoumeh Hatam
- Dept. of Physiology, Shiraz University of Medical Sciences, Shiraz, Iran.
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2
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Sandgren JA, Linggonegoro DW, Zhang SY, Sapouckey SA, Claflin KE, Pearson NA, Leidinger MR, Pierce GL, Santillan MK, Gibson-Corley KN, Sigmund CD, Grobe JL. Angiotensin AT 1A receptors expressed in vasopressin-producing cells of the supraoptic nucleus contribute to osmotic control of vasopressin. Am J Physiol Regul Integr Comp Physiol 2018; 314:R770-R780. [PMID: 29364700 PMCID: PMC6032302 DOI: 10.1152/ajpregu.00435.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 01/03/2018] [Accepted: 01/17/2018] [Indexed: 11/22/2022]
Abstract
Angiotensin II (ANG) stimulates the release of arginine vasopressin (AVP) from the neurohypophysis through activation of the AT1 receptor within the brain, although it remains unclear whether AT1 receptors expressed on AVP-expressing neurons directly mediate this control. We explored the hypothesis that ANG acts through AT1A receptors expressed directly on AVP-producing cells to regulate AVP secretion. In situ hybridization and transgenic mice demonstrated localization of AVP and AT1A mRNA in the supraoptic nucleus (SON) and the paraventricular nucleus (PVN), but coexpression of both AVP and AT1A mRNA was only observed in the SON. Mice harboring a conditional allele for the gene encoding the AT1A receptor (AT1Aflox) were then crossed with AVP-Cre mice to generate mice that lack AT1A in all cells that express the AVP gene (AT1AAVP-KO). AT1AAVP-KO mice exhibited spontaneously increased plasma and serum osmolality but no changes in fluid or salt-intake behaviors, hematocrit, or total body water. AT1AAVP-KO mice exhibited reduced AVP secretion (estimated by measurement of copeptin) in response to osmotic stimuli such as acute hypertonic saline loading and in response to chronic intracerebroventricular ANG infusion. However, the effects of these receptors on AVP release were masked by complex stimuli such as overnight dehydration and DOCA-salt treatment, which simultaneously induce osmotic, volemic, and pressor stresses. Collectively, these data support the expression of AT1A in AVP-producing cells of the SON but not the PVN, and a role for AT1A receptors in these cells in the osmotic regulation of AVP secretion.
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MESH Headings
- Angiotensin II/administration & dosage
- Angiotensin II/pharmacology
- Animals
- Body Water
- Feeding Behavior
- Injections, Intraventricular
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Osmosis
- Paraventricular Hypothalamic Nucleus/metabolism
- Receptor, Angiotensin, Type 1/biosynthesis
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/physiology
- Sodium, Dietary
- Supraoptic Nucleus/metabolism
- Supraoptic Nucleus/physiology
- Vasoconstrictor Agents/administration & dosage
- Vasoconstrictor Agents/pharmacology
- Vasopressins/biosynthesis
- Vasopressins/physiology
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Affiliation(s)
| | | | - Shao Yang Zhang
- Department of Pharmacology, University of Iowa , Iowa City, Iowa
| | | | | | - Nicole A Pearson
- Department of Pharmacology, University of Iowa , Iowa City, Iowa
| | | | - Gary L Pierce
- Department of Health and Human Physiology, University of Iowa , Iowa City, Iowa
- Center for Hypertension Research, University of Iowa , Iowa City, Iowa
- François M. Abboud Cardiovascular Research Center, University of Iowa , Iowa City, Iowa
| | - Mark K Santillan
- Department of Obstetrics and Gynecology, University of Iowa , Iowa City, Iowa
- Center for Hypertension Research, University of Iowa , Iowa City, Iowa
| | - Katherine N Gibson-Corley
- Department of Pathology, University of Iowa , Iowa City, Iowa
- Center for Hypertension Research, University of Iowa , Iowa City, Iowa
- Fraternal Order of Eagles' Diabetes Research Center, University of Iowa , Iowa City, Iowa
| | - Curt D Sigmund
- Department of Pharmacology, University of Iowa , Iowa City, Iowa
- Center for Hypertension Research, University of Iowa , Iowa City, Iowa
- François M. Abboud Cardiovascular Research Center, University of Iowa , Iowa City, Iowa
| | - Justin L Grobe
- Department of Pharmacology, University of Iowa , Iowa City, Iowa
- Center for Hypertension Research, University of Iowa , Iowa City, Iowa
- François M. Abboud Cardiovascular Research Center, University of Iowa , Iowa City, Iowa
- Iowa Neuroscience Institute, University of Iowa , Iowa City, Iowa
- Obesity Research and Education Initiative, University of Iowa , Iowa City, Iowa
- Fraternal Order of Eagles' Diabetes Research Center, University of Iowa , Iowa City, Iowa
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3
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Paz MC, Marchese NA, Stroppa MM, Gerez de Burgos NM, Imboden H, Baiardi G, Cancela LM, Bregonzio C. Involvement of the brain renin-angiotensin system (RAS) in the neuroadaptive responses induced by amphetamine in a two-injection protocol. Behav Brain Res 2014; 272:314-23. [PMID: 25046593 DOI: 10.1016/j.bbr.2014.07.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 11/25/2022]
Abstract
A single or repeated exposure to psychostimulants induces long-lasting neuroadaptative changes. Different neurotransmitter systems are involved in these responses including the neuropeptide angiotensin II. Our study tested the hypothesis that the neuroadaptative changes induced by amphetamine produce alterations in brain RAS components that are involved in the expression of the locomotor sensitization to the psychostimulant drug. Wistar male rats, pretreated with amphetamine were used 7 or 21 days later to study AT1 receptors by immunohistochemistry and western blot and also angiotensinogen mRNA and protein in caudate putamen and nucleus accumbens. A second group of animals was used to explore the possible role of Ang II AT1 receptors in the expression of behavioral sensitization. In these animals treated in the same way, bearing intra-cerebral cannula, the locomotor activity was tested 21 days later, after an amphetamine challenge injection and the animals received an AT1 blocker, losartan, or saline 5min before the amphetamine challenge. An increase of AT1 receptor density induced by amphetamine was found in both studied areas and a decrease in angiotensinogen mRNA and protein only in CPu at 21 days after treatment; meanwhile, no changes were established in NAcc. Finally, the increased locomotor activity induced by amphetamine challenge was blunted by losartan administration in CPu. No differences were detected in the behavioral sensitization when the AT1 blocker was injected in NAcc. Our results support the hypothesis of a key role of brain RAS in the neuroadaptative changes induced by amphetamine.
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Affiliation(s)
- Maria Constanza Paz
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba (UNC), Argentina
| | - Natalia Andrea Marchese
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba (UNC), Argentina
| | - Maria Mercedes Stroppa
- Cátedra de Bioquímica y Biología Molecular, Facultad de Ciencias Médicas, UNC, Argentina
| | | | - Hans Imboden
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Gustavo Baiardi
- Laboratorio de Neurofarmacología, Instituto de Investigaciones Biológicas y Tecnológicas (IIBYT- CONICET), Universidad Nacional de Córdoba. Facultad de Ciencias Quimicas, Universidad Católica de Córdoba
| | - Liliana Marina Cancela
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba (UNC), Argentina
| | - Claudia Bregonzio
- Instituto de Farmacología Experimental Córdoba (IFEC-CONICET), Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba (UNC), Argentina.
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4
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Sharma NM, Zheng H, Li YF, Patel KP. Nitric oxide inhibits the expression of AT1 receptors in neurons. Am J Physiol Cell Physiol 2012; 302:C1162-73. [PMID: 22218225 DOI: 10.1152/ajpcell.00258.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously observed an increased of angiotensin II (ANG II) type 1 receptor (AT(1)R) with enhanced AT(1)R-mediated sympathetic outflow and concomitant downregulation of neuronal nitric oxide (NO) synthase (nNOS) with reduced NO-mediated inhibition from the paraventricular nucleus (PVN) in rats with heart failure. To test the hypothesis that NO exerts an inhibitory effect on AT(1)R expression in the PVN, we used primary cultured hypothalamic cells of neonatal rats and neuronal cell line NG108-15 as in vitro models. In hypothalamic primary culture, NO donor sodium nitroprusside (SNP) induced dose-dependent decreases in mRNA and protein of AT(1)R (10(-5) M SNP, AT(1)R protein was 10 ± 2% of control level) while NOS inhibitor N(G)-monomethyl-l-arginine (l-NMMA) induced dose-dependent increases in mRNA and protein levels of AT(1)R (10(-5) M l-NMMA, AT(1)R protein was 148 ± 8% of control level). Similar effects of SNP and l-NMMA on AT(1)R expression were also observed in NG108-15 cell line (10(-6) M SNP, AT(1)R protein was 30 ± 4% of control level while at the dose of 10(-6) M l-NMMA, AT(1)R protein was 171 ± 15% of the control level). Specific inhibition of nNOS, using antisense, caused an increase in AT(1)R expression while overexpression of nNOS, using adenoviral gene transfer (Ad.nNOS), caused an inhibition of AT(1)R expression in NG108 cells. Antisense nNOS transfection augmented the increase while Ad.nNOS infection blunted the increase in intracellular calcium concentration in response to ANG II treatment in NG108 cells. In addition, downregulation of AT(1)R mRNA as well as protein level in neuronal cell line in response to S-nitroso-N-acetyl pencillamine (SNAP) treatment was blocked by protein kinase G (PKG) inhibitor, while the peroxynitrite scavenger deforxamine had no effect. These results suggest that NO acts as an inhibitory regulator of AT(1)R expression and the activation of PKG is the required step in the regulation of AT(1)R gene expression via cGMP-dependent signaling pathway.
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Affiliation(s)
- Neeru M Sharma
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, 68198-5850, USA
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5
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Zubcevic J, Waki H, Raizada MK, Paton JFR. Autonomic-immune-vascular interaction: an emerging concept for neurogenic hypertension. Hypertension 2011; 57:1026-33. [PMID: 21536990 DOI: 10.1161/hypertensionaha.111.169748] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Jasenka Zubcevic
- Department of Physiology and Functional Genomics, McKnight Brain Institute, 1600 SW Archer Rd, Gainesville, FL 32610, USA
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6
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Kc P, Dick TE. Modulation of cardiorespiratory function mediated by the paraventricular nucleus. Respir Physiol Neurobiol 2010; 174:55-64. [PMID: 20708107 DOI: 10.1016/j.resp.2010.08.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 08/01/2010] [Accepted: 08/02/2010] [Indexed: 10/19/2022]
Abstract
The hypothalamic paraventricular nucleus (PVN) coordinates autonomic and neuroendocrine systems to maintain homeostasis and to respond to stress. Neuroanatomic and neurophysiologic experiments have provided insight into the mechanisms by which the PVN acts. The PVN projects directly to the spinal cord and brainstem and, specifically, to sites that control cardio-respiratory function: the intermediolateral cell columns and phrenic motor nuclei in the spinal cord and rostral ventrolateral medulla (RVLM) and the rostral nuclei in the ventral respiratory column (rVRC) in the brainstem. Activation of the PVN increases ventilation (both tidal volume and frequency) and blood pressure (both heart rate and sympathetic nerve activity). Excitatory and inhibitory neurotransmitters including glutamate and GABA converge in the PVN to influence its neuronal activity. However, a tonic GABAergic input to the PVN directly modulates excitatory outflow from the PVN. Further, even within the PVN, microinjection of GABA(A) receptor blockers increases glutamate release suggesting an indirect mechanism by which GABA control contributes to PVN functions. PVN activity alters blood pressure and ventilation during various stresses, such as maternal separation, chronic intermittent hypoxia (CIH), dehydration and hemorrhage. Among the several PVN neurotransmitters and neurohormones, vasopressin and oxytocin modulate ventilation and blood pressure. Here, we review our data indicating that increases in vasopressin and vasopressin type 1A (V(1A)) receptor signalling in the RVLM and rVRC are mechanisms increasing blood pressure and ventilation after exposure to CIH. That blockade of V(1A) receptors in the medulla normalizes baseline blood pressure as well as blunts PVN-evoked blood pressure and ventilatory responses in CIH-conditioned animals indicate the role of vasopressin in cardiorespiratory control. In summary, morphological and functional studies have found that the PVN integrates sensory input and projects to the sympathetic and respiratory control systems with descending projections to the medulla and spinal cord.
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Affiliation(s)
- Prabha Kc
- Department of Pediatrics, Division of Neonatology, Case Western Reserve University, Cleveland, OH 44106-6010, USA.
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7
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Zheng H, Li YF, Wang W, Patel KP. Enhanced angiotensin-mediated excitation of renal sympathetic nerve activity within the paraventricular nucleus of anesthetized rats with heart failure. Am J Physiol Regul Integr Comp Physiol 2009; 297:R1364-74. [PMID: 19710393 DOI: 10.1152/ajpregu.00149.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic heart failure (HF) is characterized by increased sympathetic drive. Enhanced angiotensin II (ANG II) activity may contribute to the increased sympathoexcitation under HF condition. The present study examined sympathoexcitation by 1) the effects of ANG II in the paraventricular nucleus (PVN) on renal sympathetic nerve activity (RSNA), and 2) the altered ANG II type 1 (AT(1)) receptor expression during HF. Left coronary artery ligation was used to induce HF. In the anesthetized Sprague-Dawley rats, microinjection of ANG II (0.05-1 nmol) into the PVN increased RSNA, mean arterial pressure (MAP), and heart rate (HR) in both sham-operated and HF rats. The responses of RSNA and HR were significantly enhanced in rats with HF compared with sham rats (RSNA: 64 +/- 8% vs. 33 +/- 4%, P < 0.05). Microinjection of AT(1) receptor antagonist losartan into the PVN produced a decrease of RSNA, MAP, and HR in both sham and HF rats. The RSNA and HR responses to losartan in HF rats were significantly greater (RSNA: -25 +/- 4% vs. -13 +/- 1%, P < 0.05). Using RT-PCR and Western blot analysis, we found that there were significant increases in the AT(1) receptor mRNA (Delta186 +/- 39%) and protein levels (Delta88 +/- 20%) in the PVN of rats with HF (P < 0.05). The immunofluorescence of AT(1) receptors was significantly higher in the PVN of rats with HF. These data support the conclusion that an increased angiotensinergic activity on sympathetic regulation, due to the upregulation of ANG II AT(1) receptors within the PVN, may contribute to the elevated sympathoexcitation that is observed during HF.
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Affiliation(s)
- Hong Zheng
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska 68198-5850, USA.
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8
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Thomas MA, Lemmer B. The use of heat-induced hydrolysis in immunohistochemistry on angiotensin II (AT1) receptors enhances the immunoreactivity in paraformaldehyde-fixed brain tissue of normotensive Sprague–Dawley rats. Brain Res 2006; 1119:150-64. [PMID: 17010318 DOI: 10.1016/j.brainres.2006.08.056] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Revised: 08/10/2006] [Accepted: 08/15/2006] [Indexed: 11/28/2022]
Abstract
The research on components of the renin-angiotensin system delivered a broad image of angiotensin II-binding sites. Especially, immunohistochemistry (IHC) provided an exact anatomical localization of the AT(1) receptor in the rat brain. Yet, controversial results between in vitro receptor autoradiography and IHC as well as between immunohistochemical studies using various antisera started a vehement discussion concerning specificity and cross-reactivity of these antisera. In particular the magnocellular subdivision of the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) provided controversial results on the localization of AT(1) receptors. Both areas are known for angiotensin II-induced release of vasopressin (VP) and oxytocin (OXT). To evaluate the significance of the appropriate method of antigen retrieval and its relevance for the detection of AT(1) receptors we performed IHC on AT(1) receptors in paraformaldehyde-fixed and paraffin-embedded brain tissue of Sprague-Dawley rats using either the detergent Triton X-100 or microwave oven heating. This study demonstrates that heat-induced hydrolysis enhances the quality and quantity of immunoreactivity (IR) in IHC on AT(1) receptors. In the organum vasculosum lamina terminalis and in the parvocellular subdivisions of the PVN we report a distribution of AT(1)-like-IR similar to that observed with other methods. However, in addition, we provide evidence that distinct AT(1)-like-IR is also localized in few magnocellular neurons of the PVN and in few parvocellular neurons of the dorsal SON but not in magnocellular neurons of the SON. Moreover, parallel IHC indicates that few magnocellular OXT- or VP-releasing neurons of the PVN as well as parvocellular OXT-releasing neurons of the SON do also contain AT(1) receptors.
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Affiliation(s)
- Martin Alexander Thomas
- Institute of Pharmacology and Toxicology, Ruprecht-Karls University of Heidelberg, 68169 Mannheim, Germany.
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9
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Hoffmann A, Cool DR. Characterization of two polyclonal peptide antibodies that recognize the carboxy terminus of angiotensin II AT1A and AT1B receptors. Clin Exp Pharmacol Physiol 2006; 32:936-43. [PMID: 16405450 DOI: 10.1111/j.1440-1681.2005.04288.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. The differential identification of the angiotensin AT1A and AT1B receptor subtypes is impaired by the existing>96% homology of both receptors. In the present study, we characterized two polyclonal rabbit peptide antibodies, namely alpha-AT1A and alpha-AT1B, that recognize the C-terminal region of mouse AT1A and AT1B receptors, respectively. 2. In immunoblotting, both antibodies detected two major AT1 receptor-specific bands at sizes of 72.5 and 87.6 kDa in mouse tissues and in Neuro-2a cell lysates. In immunohistochemistry, antibodies demonstrated AT1 receptor-specific staining in renal proximal and distal tubules, as well as in kidney glomeruli. In addition, both antibodies stained AT1 receptors in Neuro-2a cells with G-protein receptor typical distribution. Dot-blot and ELISA analysis of the alpha-AT1A antibody showed 2.5- to fourfold higher selectivity for its AT1A receptor target peptide (1A-PEP) compared with the non-specific AT1B receptor peptide (1B-PEP). In contrast, the alpha-AT1B antibody showed high binding affinity towards its target peptide 1B-PEP, but also demonstrated high cross-reactivity for the non-specific peptide 1A-PEP (1.4- to twofold in ELISA and dot-blot analysis). In contrast with the lack of recognition by the alpha-AT1B antibody, the alpha-AT1A antibody selectively recognized the AT1A receptor fused to red fluorescence protein in transiently transfected Chinese hamster ovary cells. 3. In summary, we have generated two new peptide antibodies to the mouse AT1A and AT1B receptors (alpha-AT1A and alpha-AT1B), of which the alpha-AT1A antibody has the capability to distinguish AT1A receptor types in immunological approaches.
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Affiliation(s)
- Andrea Hoffmann
- Department of Pharmacology and Toxicology, Wright State University School of Medicine, Dayton, Ohio 45435, USA.
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Li YF, Wang W, Mayhan WG, Patel KP. Angiotensin-mediated increase in renal sympathetic nerve discharge within the PVN: role of nitric oxide. Am J Physiol Regul Integr Comp Physiol 2005; 290:R1035-43. [PMID: 16322353 DOI: 10.1152/ajpregu.00338.2004] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The paraventricular nucleus (PVN) of the hypothalamus is known to be an important site of integration in the central nervous system for sympathetic outflow. ANG II and nitric oxide (NO) play an important role in regulation of sympathetic nerve activity. The purpose of the present study was to examine how the interaction between NO and ANG II within the PVN affects sympathetic outflow in rats. Renal sympathetic nerve discharge (RSND), arterial blood pressure (AP), and heart rate (HR) were measured in response to administration of ANG II and N(G)-monomethyl-l-arginine (L-NMMA) into the PVN. Microinjection of ANG II (0.05, 0.5, and 1.0 nmol) into the PVN increased RSND, AP, and HR in a dose-dependent manner, resulting in increases of 53 +/- 9%, 19 +/- 3 mmHg, and 32 +/- 12 beats/min from baseline, respectively, at the highest dose. These responses were significantly enhanced by prior microinjection of L-NMMA and were blocked by losartan, an ANG II type 1 receptor antagonist. Similarly, administration of antisense to neuronal NO synthase within the PVN also potentiated the ANG II responses. Conversely, overexpression of neuronal NOS within the PVN with adenoviral gene transfer significantly attenuated ANG II responses. Push-pull administration of ANG II (1 nmol) into the PVN induced an increase in NO release. Our data indicate that ANG II type 1 receptors within the PVN mediate an excitatory effect on RSND, AP, and HR. NO in the PVN, which can be induced by ANG II stimulation, in turn inhibits the ANG II-mediated increase in sympathetic nerve activity. This negative-feedback mechanism within the PVN may play an important role in maintaining the overall balance and tone of sympathetic outflow.
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Affiliation(s)
- Yi-Fan Li
- Division of Basic Biomedical Science, College of Medicine, University of South Dakota, Vermillion, South Dakota, USA
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11
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Fleegal MA, Sumners C. Drinking behavior elicited by central injection of angiotensin II: roles for protein kinase C and Ca2+/calmodulin-dependent protein kinase II. Am J Physiol Regul Integr Comp Physiol 2003; 285:R632-40. [PMID: 12738610 DOI: 10.1152/ajpregu.00151.2003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prior studies utilizing neurons cultured from the hypothalamus and brain stem of newborn rats have demonstrated that ANG II-induced modulation of neuronal firing involves activation of both protein kinase C (PKC) and Ca2+/calmodulin-dependent protein kinase II (CaMKII). The present studies were performed to determine whether these signaling molecules are also involved in physiological responses elicited by ANG II in the brain in vivo. Central injection of ANG II (10 ng/2 microl) into the lateral cerebroventricle (icv) of Sprague-Dawley rats increased water intake in a time-dependent manner. This ANG II-mediated dipsogenic response was attenuated by central injection of the PKC inhibitors chelerythrine chloride (0.5-50 microM, 2 microl) and Go-6976 (2.3 nM, 2 microl) and by the CaMKII inhibitor KN-93 (10 microM, 2 microl). Conversely, icv injection of chelerythrine chloride (50 microM, 2 microl) and KN-93 (10 microM, 2 microl) had no effect on the dipsogenic response elicited by central injection of carbachol (200 ng/2 microl). Furthermore, injection of ANG II (10 ng/2 microl) icv increases the activity of both PKC-alpha and CaMKII in rat septum and hypothalamus. These data suggest that signaling molecules involved in ANG II-induced responses in vitro are also relevant in physiological responses elicited by ANG II in the whole animal model.
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Affiliation(s)
- Melissa A Fleegal
- Dept. of Physiology and Functional Genomics, P.O. Box 100274, Univ. of Florida, Gainesville, FL 32610, USA
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12
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Li YF, Patel KP. Paraventricular nucleus of the hypothalamus and elevated sympathetic activity in heart failure: the altered inhibitory mechanisms. ACTA PHYSIOLOGICA SCANDINAVICA 2003; 177:17-26. [PMID: 12492775 DOI: 10.1046/j.1365-201x.2003.01043.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIM There is a characteristic neurohumoral activation in heart failure (HF). However, few studies have been performed to examine the role of the central nervous system in the activation of sympathetic outflow during HF. In this paper we review some of our studies, with particular emphasis on examining the role of the paraventricular nucleus (PVN) in the exaggerated sympathetic outflow commonly observed in HF. RESULTS Our studies have revealed that the inhibitory mechanisms regulating sympathetic outflow are mediated by nitric oxide (NO) and gamma-aminobutyric acid (GABA) within the PVN and are attenuated in HF. These alterations are associated with elevated sympathetic activity. Furthermore, these studies have indicated that the interactions among excitatory (angiotensin II and glutamate) and inhibitory (NO and GABA) neurotransmitters/mediators within the PVN significantly influence sympathetic outflow. CONCLUSION Reduced inhibitory actions of NO and/or GABA within the PVN may exaggerate an increase in the actions of excitatory neurotransmitters such as glutamate and angiotensin II within the PVN and this may contribute to the overall sympatho-excitation commonly observed in HF.
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Affiliation(s)
- Y-F Li
- Department of Physiology and Biophysics, University of Nebraska Medical Center, 984575 Nebraska Medical Center, Omaha, NE 68198-4575, USA
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13
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Hu L, Zhu DN, Yu Z, Wang JQ, Sun ZJ, Yao T. Expression of angiotensin II type 1 (AT(1)) receptor in the rostral ventrolateral medulla in rats. J Appl Physiol (1985) 2002; 92:2153-61. [PMID: 11960969 DOI: 10.1152/japplphysiol.00261.2001] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, the changes of amino acids release in the spinal cord after the application of angiotensin II (ANG II) in the rostral ventrolateral medulla (RVLM) and the distribution of ANG receptors on neurons of the RVLM were investigated. A microdialysis experiment showed that microinjection of angiotensin II into the RVLM significantly (P < 0.01) increased the release of aspartate and glutamate in the intermediolateral column of the spinal cord. Immunofluorescence technique combined with confocal microscopy demonstrated that most of the glutamatergic and GABAergic neurons in the RVLM of both Wistar and spontaneously hypertensive rats (SHR) were double labeled with ANG type 1 (AT1) receptor. Immunocytochemical studies demonstrated that the mean optic density of AT1 receptor of the cell surface as well as the whole cell was higher (P < 0.05) in SHR than that in Wistar rats, indicating that the higher expression of AT1 receptors in the RVLM may contribute to the higher responsiveness of SHR to ANG II stimulation. Immunogold staining and electronmicroscopic study demonstrated that AT1 receptor in the RVLM was distributed on the rough endoplasmic reticulum, cell membrane, and nerve processes. The results suggest that effects evoked by ANG II in the RVLM are closely related to glutamatergic and GABAergic pathways. These results indirectly support the hypothesis that ANG II in the RVLM may activate vasomotor sympathetic glutamatergic neurons, leading to an increase in sympathetic nerve activity and arterial blood pressure.
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Affiliation(s)
- Lian Hu
- Department of Physiology, Medical Center of Fudan University (Former Shanghai Medical University), Shanghai 200032, China
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14
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Frei N, Weissenberger J, Beck-Sickinger AG, Höfliger M, Weis J, Imboden H. Immunocytochemical localization of angiotensin II receptor subtypes and angiotensin II with monoclonal antibodies in the rat adrenal gland. REGULATORY PEPTIDES 2001; 101:149-55. [PMID: 11495690 DOI: 10.1016/s0167-0115(01)00278-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Angiotensin II (Ang II), a major regulator of cardiovascular function and body fluid homeostasis, mediates its biological actions via two subtypes of G protein-coupled receptors, termed AT(1) and AT(2). The primary goal of this study was to raise monoclonal anti-peptide antibodies specific to angiotensin AT(1)- and AT(2)-receptor subtypes and to Ang II itself and using these monoclonal antibodies to determine the intraadrenal localization of AT(1) and AT(2) receptors and Ang II in male adult rats. Immunocytochemistry unambiguously demonstrates a regional colocalization of Ang II and angiotensin II receptors in the adrenal gland. The novel antibodies localized Ang II and the AT(1) receptors to the zona glomerulosa of the cortex and to the medulla whereas AT(2) receptors were limited to the medulla. The specificity of immunostaining was documented by pre-adsorption of the antibody with the immunogenic peptide. Our data underscore that AT(1) appears to mediate most of the physiological actions of Ang II in adrenal. Western blot analysis of rat adrenal protein extracts using AT(1) antibody showed a predominant 73-kDa band and a weaker 97-kDa immunoreactive band corresponding to glycosylated forms of the AT(1) receptor. Immunostaining with anti-AT(2) yielded one major immunoreactive band of 73-kDa size and one additional fainter band of 120 kDa. These antibodies may prove of value in unraveling the subcellular localization and intracellular effector pathways of AT(1) and AT(2).
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MESH Headings
- Adrenal Glands/chemistry
- Adrenal Medulla/chemistry
- Amino Acid Sequence
- Angiotensin II/analysis
- Angiotensin II/immunology
- Animals
- Antibodies, Monoclonal/immunology
- Blotting, Western
- Glycosylation
- Immunohistochemistry
- Male
- Rats
- Rats, Inbred WKY
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/analysis
- Receptors, Angiotensin/immunology
- Receptors, Angiotensin/metabolism
- Sensitivity and Specificity
- Zona Glomerulosa/chemistry
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Affiliation(s)
- N Frei
- Division of Neurobiology, Institute of Zoology, University of Berne, Baltzerstr. 6, CH-3012, Berne, Switzerland
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15
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Hurbin A, Orcel H, Ferraz C, Moos FC, Rabié A. Expression of the genes encoding the vasopressin-activated calcium-mobilizing receptor and the dual angiotensin II/vasopressin receptor in the rat central nervous system. J Neuroendocrinol 2000; 12:677-84. [PMID: 10849213 DOI: 10.1046/j.1365-2826.2000.00499.x] [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: 11/20/2022]
Abstract
The distributions of two newly discovered receptors, the vasopressin-activated calcium-mobilizing receptor (VACM-1) and the dual angiotensin II/vasopressin receptor (AII/AVP), in the central nervous system (CNS) of the rat were determined using reverse transcriptase-polymerase chain reaction and in situ hybridization. The sequence of the rat VACM-1 cDNA was determined and found very homologous to the rabbit and human sequences. Both VACM-1 and AII/AVP receptor genes were widely expressed in the brain, but differed according to the cell type studied. Glial cells were very faintly labelled. The epithelial cells of the choroid plexuses, the ependymal cells and the pia mater were all labelled. Both genes were most active in neurones throughout the CNS. VACM-1 and AII/AVP receptors were detected in neurones previously shown to possess V1a and V1b vasopressin receptors, and/or the AT1 and AT2 angiotensin II receptors in many brain areas. This was the case for the magnocellular neurones of the supraoptic and paraventricular nuclei of the hypothalamus. We suggest that the VACM-1 and AII/AVP receptors may account for the V2-like responses to vasopressin by these neurones which lack a genuine V2 vasopressin receptor.
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Affiliation(s)
- A Hurbin
- CNRS-UPR 9055, Biologie des Neurones Endocrines, CCIPE and CNRS-UPR 1142, Institut de Génétique Humaine, Montpellier, France
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16
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Egli M, Laurent JP, Mosimann R, Felix D, Imboden H. Morphological and immunocytochemical characterization of electrophysiologically investigated neurons in the PVN of the rat. J Neurosci Methods 2000; 95:145-50. [PMID: 10752485 DOI: 10.1016/s0165-0270(99)00166-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This study was carried out to characterize angiotensin II (ANG II) sensitive neurons in the hypothalamic paraventricular nucleus (PVN) of the rat. An approach was chosen in which a combination of an electrophysiological, a morphological, and an immunocytochemical method was focused on one single neuron. The cell's reaction to an application of ANG II and its specific antagonist Losartan (Dup753) was investigated using the technique of intracellular recording inside 450-microm-thick brain slices. A final injection of a fluorescent dye labelled the neurons. Optical sections were taken through the marked cells by a confocal laser-scanning microscope and made into a three-dimensional cell model on a computer. One-micrometer thin sections were cut from the thick slice at the level of the electrophysiologically characterized and marked cell body for immunocytochemical tests with different antibodies. Our results show an example of such a neuron inside the PVN excited by ANG II. It was possible to block this excitation with the specific ANG II receptor subtype 1 (AT1) antagonist Losartan. The result indicated that the ANG II reaction was mediated by the AT1 receptor subtype. Immunocytochemical studies show that this ANG II-sensitive neuron contains ANG II but no vasopressin. The combination of the results enables us to gain improved information on interactions of peptidergic systems.
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Affiliation(s)
- M Egli
- Division of Neurobiology, University of Berne, Switzerland
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17
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Abstract
In mammalian brain, angiotensin II AT1 and AT2 receptor subtypes are apparently expressed only in neurons and not in glia. AT1 and AT2 receptor subtypes are sometimes closely associated, but apparently expressed in different neurons. Brain AT1/AT2 interactions may occur in selective cases as inter-neuron cross talk. There are two AT1 isoforms in rodents. AT1A, which predominates, and AT1B. There are also important inter-species differences in receptor expression. Relative lack of amino acid conservation in the gerbil gAT1A receptor substantially decreases affinity for the AT1 antagonists. AT1 receptors are expressed in brain areas regulating autonomic and hormonal responses. AT1A receptors are heterogeneously regulated in a number of experimental conditions. In specific areas, AT1A receptors are not normally expressed, but are induced under influence of reproductive hormones in dopaminergic neurons. There are AT1 and AT2 receptors also in areas related to limbic, sensory and motor functions and their expression is developmentally regulated. A picture is emerging of widespread, neuronally localized, heterogeneously regulated, closely associated brain angiotensin receptor subtypes, modulating multiple functions including neuroendocrine and autonomic responses, stress, cerebrovascular flow, and perhaps brain maturation, neuronal plasticity, memory and behavior.
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Affiliation(s)
- J M Saavedra
- Section on Pharmacology, National Institute of Mental Health, Bethesda, MD 20892, USA.
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18
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Rosas-Arellano MP, Solano-Flores LP, Ciriello J. Co-localization of estrogen and angiotensin receptors within subfornical organ neurons. Brain Res 1999; 837:254-62. [PMID: 10434010 DOI: 10.1016/s0006-8993(99)01672-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A double-staining immunocytochemical study was done in ovariectomized (OVX) female rats that were either treated with 17beta-estradiol (E(2)) (OVX+E(2)) to produce an approximate circulating level of 30 pg/ml plasma, or not-treated with E(2) (OVX), to investigate the distribution of subfornical organ (SFO) neurons that contained estrogen receptors (ER), and to determine whether these neurons also contained the angiotensin II AT(1)-receptor (AT(1)R). Neurons that contained either ER-like immunoreactivity only, AT(1)R-like immunoreactivity only, or both ER and AT(1)R immunoreactivity were found throughout the extent of the SFO in both the OVX+E(2) and OVX rats. However, some regional differences were apparent in both groups of female rats. Neurons containing the ER were predominantly found in the peripheral regions of the SFO, near large blood vessels and the ependymal layer of the third ventricle. A number of lightly stained ER containing neurons was also observed scattered throughout the central core region of the SFO. OVX only animals were found to have a larger number of ER containing neurons in the SFO compared to the E(2) treated animals. Neurons containing AT(1)R were also found throughout the SFO, but without a distinct distribution pattern in either group of rats, although there were more neurons that exhibited AT(1)R immunoreactivity in the OVX animals. Finally, a distinct group of SFO neurons was found that exhibited both ER and AT(1)R immunoreactivity in both groups of animals, although a larger number of these double labelled neurons was found in the OVX animal. Most of these neurons were also found along the peripheral border of the SFO in close proximity to blood vessels and the ventricular lining. These data have demonstrated the co-existence of ER and AT(1)R in SFO neurons of the female rat, and suggest that circulating level of E(2) alter the expression of both the ER and AT(1)R in these neurons. In addition, these data suggest that E(2) may alter the physiological responses of SFO neurons to angiotensin II by down regulating the number of AT(1)R.
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Affiliation(s)
- M P Rosas-Arellano
- Department of Physiology, Health Sciences Centre, University of Western Ontario, London, ON, Canada
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Richards EM, Raizada MK, Gelband CH, Sumners C. Angiotensin II type 1 receptor-modulated signaling pathways in neurons. Mol Neurobiol 1999; 19:25-41. [PMID: 10321970 DOI: 10.1007/bf02741376] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mammalian brain contains high densities of angiotensin II (Ang II) type 1 (AT1) receptors, localized mainly to specific nuclei within the hypothalamus and brainstem regions. Neuronal AT1 receptors within these areas mediate the stimulatory actions of central Ang II on blood pressure, water and sodium intake, and vasopressin secretion, effects that involve the modulation of brain noradrenergic pathways. This review focuses on the intracellular events that mediate the functional effects of Ang II in neurons, via AT1 receptors. The signaling pathways involved in short-term changes in neuronal activity, membrane ionic currents, norepinephrine (NE) release, and longer-term neuromodulatory actions of Ang II are discussed. It will be apparent from this discussion that the signaling pathways involved in these events are often distinct.
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Affiliation(s)
- E M Richards
- Department of Physiology, College of Medicine, University of Florida, Gainesville 32610, USA
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