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Liu H, Xue Y, Chen L. Angiotensin II increases the firing activity of pallidal neurons and participates in motor control in rats. Metab Brain Dis 2023; 38:573-587. [PMID: 36454502 DOI: 10.1007/s11011-022-01127-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 11/22/2022] [Indexed: 12/05/2022]
Abstract
The globus pallidus has emerged as a crucial node in the basal ganglia motor control circuit under both healthy and parkinsonian states. Previous studies have shown that angiotensin II (Ang II) and angiotensin subtype 1 receptor (AT1R) are closely related to Parkinson's disease (PD). Recent morphological study revealed the expression of AT1R in the globus pallidus of mice. To investigate the functions of Ang II/AT1R on the globus pallidus neurons of both normal and parkinsonian rats, electrophysiological recordings and behavioral tests were performed in the present study. Electrophysiological recordings showed that exogenous and endogenous Ang II mainly excited the globus pallidus neurons through AT1R. Behavioral tests further demonstrated that unilateral microinjection of Ang II into the globus pallidus induced significantly contralateral-biased swing in elevated body swing test (EBST), and bilateral microinjection of Ang II into the globus pallidus alleviated catalepsy and akinesia caused by haloperidol. AT1R was involved in Ang II-induced behavioral effects. Immunostaining showed that AT1R was expressed in the globus pallidus of rats. On the basis of the present findings, we concluded that pallidal Ang II/AT1R alleviated parkinsonian motor deficits through activating globus pallidus neurons, which will provide a rationale for further investigations into the potential of Ang II in the treatment of motor disorders originating from the basal ganglia.
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Affiliation(s)
- Hongxia Liu
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
- Department of Physiology, Binzhou Medical University, Yantai, China
| | - Yan Xue
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, China.
| | - Lei Chen
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, China.
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2
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Baumer-Harrison C, Breza JM, Sumners C, Krause EG, de Kloet AD. Sodium Intake and Disease: Another Relationship to Consider. Nutrients 2023; 15:535. [PMID: 36771242 PMCID: PMC9921152 DOI: 10.3390/nu15030535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/14/2023] [Accepted: 01/15/2023] [Indexed: 01/22/2023] Open
Abstract
Sodium (Na+) is crucial for numerous homeostatic processes in the body and, consequentially, its levels are tightly regulated by multiple organ systems. Sodium is acquired from the diet, commonly in the form of NaCl (table salt), and substances that contain sodium taste salty and are innately palatable at concentrations that are advantageous to physiological homeostasis. The importance of sodium homeostasis is reflected by sodium appetite, an "all-hands-on-deck" response involving the brain, multiple peripheral organ systems, and endocrine factors, to increase sodium intake and replenish sodium levels in times of depletion. Visceral sensory information and endocrine signals are integrated by the brain to regulate sodium intake. Dysregulation of the systems involved can lead to sodium overconsumption, which numerous studies have considered causal for the development of diseases, such as hypertension. The purpose here is to consider the inverse-how disease impacts sodium intake, with a focus on stress-related and cardiometabolic diseases. Our proposition is that such diseases contribute to an increase in sodium intake, potentially eliciting a vicious cycle toward disease exacerbation. First, we describe the mechanism(s) that regulate each of these processes independently. Then, we highlight the points of overlap and integration of these processes. We propose that the analogous neural circuitry involved in regulating sodium intake and blood pressure, at least in part, underlies the reciprocal relationship between neural control of these functions. Finally, we conclude with a discussion on how stress-related and cardiometabolic diseases influence these circuitries to alter the consumption of sodium.
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Affiliation(s)
- Caitlin Baumer-Harrison
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Joseph M. Breza
- Department of Psychology, College of Arts and Sciences, Eastern Michigan University, Ypsilanti, MI 48197, USA
| | - Colin Sumners
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Eric G. Krause
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
| | - Annette D. de Kloet
- Department of Physiology and Aging, College of Medicine, University of Florida, Gainesville, FL 32603, USA
- Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL 32610, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL 32610, USA
- Evelyn F. and William L. McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
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3
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Zhao Y, Qin F, Han S, Li S, Zhao Y, Wang H, Tian J, Cen X. MicroRNAs in drug addiction: Current status and future perspectives. Pharmacol Ther 2022; 236:108215. [DOI: 10.1016/j.pharmthera.2022.108215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 05/11/2022] [Accepted: 05/16/2022] [Indexed: 12/21/2022]
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4
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Callera JC, De Luca LA, Menani JV. Involvement of V1-type vasopressin receptors on NaCl intake by hyperosmotic rats treated with muscimol in the lateral parabrachial nucleus. Neurosci Lett 2022; 778:136601. [DOI: 10.1016/j.neulet.2022.136601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/25/2022] [Accepted: 03/26/2022] [Indexed: 11/29/2022]
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5
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Angiotensin-II Modulates GABAergic Neurotransmission in the Mouse Substantia Nigra. eNeuro 2021; 8:ENEURO.0090-21.2021. [PMID: 33771900 PMCID: PMC8174047 DOI: 10.1523/eneuro.0090-21.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 03/22/2021] [Indexed: 11/26/2022] Open
Abstract
GABAergic projections neurons of the substantia nigra reticulata (SNr), through an extensive network of dendritic arbors and axon collaterals, provide robust inhibitory input to neighboring dopaminergic neurons in the substantia nigra compacta (SNc). Angiotensin-II (Ang-II) receptor signaling increases SNc dopaminergic neuronal sensitivity to insult, thus rendering these cells susceptible to dysfunction and destruction. However, the mechanisms by which Ang-II regulates SNc dopaminergic neuronal activity are unclear. Given the complex relationship between SN dopaminergic and GABAergic neurons, we hypothesized that Ang-II could regulate SNc dopaminergic neuronal activity directly and indirectly by modulating SNr GABAergic neurotransmission. Here, using transgenic mice, slice electrophysiology, and optogenetics, we provide evidence of an AT1 receptor-mediated signaling mechanism in SNr GABAergic neurons where Ang-II suppresses electrically-evoked neuronal output by facilitating postsynaptic GABAA receptors (GABAARs) and prolonging the action potential (AP) duration. Unexpectedly, Ang-II had no discernable effects on the electrical properties of SNc dopaminergic neurons. Also, and indicating a nonlinear relationship between electrical activity and neuronal output, following phasic photoactivation of SNr GABAergic neurons, Ang-II paradoxically enhanced the feedforward inhibitory input to SNc dopaminergic neurons. In sum, our observations describe an increasingly complex and heterogeneous response of the SN to Ang-II by revealing cell-specific responses and nonlinear effects on intranigral GABAergic neurotransmission. Our data further implicate the renin-angiotensin-system (RAS) as a functionally relevant neuromodulator in the substantia nigra, thus underscoring a need for additional inquiry.
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Su C, Xue J, Ye C, Chen A. Role of the central renin‑angiotensin system in hypertension (Review). Int J Mol Med 2021; 47:95. [PMID: 33846799 PMCID: PMC8041481 DOI: 10.3892/ijmm.2021.4928] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 01/25/2021] [Indexed: 12/16/2022] Open
Abstract
Present in more than one billion adults, hypertension is the most significant modifiable risk factor for mortality resulting from cardiovascular disease. Although its pathogenesis is not yet fully understood, the disruption of the renin-angiotensin system (RAS), consisting of the systemic and brain RAS, has been recognized as one of the primary reasons for several types of hypertension. Therefore, acquiring sound knowledge of the basic science of RAS and the under- lying mechanisms of the signaling pathways associated with RAS may facilitate the discovery of novel therapeutic targets with which to promote the management of patients with cardiovascular and kidney disease. In total, 4 types of angiotensin II receptors have been identified (AT1R-AT4R), of which AT1R plays the most important role in vasoconstriction and has been most extensively studied. It has been found in several regions of the brain, and its distribution is highly associated with that of angiotensin-like immunoreactivity in nerve terminals. The effect of AT1R involves the activation of multiple media and signaling pathways, among which the most important signaling pathways are considered to be AT1R/JAK/STAT and Ras/Raf/MAPK pathways. In addition, the regulation of the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and cyclic AMP response element-binding (CREB) pathways is also closely related to the effect of ATR1. Their mechanisms of action are related to pro-inflammatory and sympathetic excitatory effects. Central AT1R is involved in almost all types of hypertension, including spontaneous hypertension, salt-sensitive hypertension, obesity-induced hypertension, renovascular hypertension, diabetic hypertension, L-NAME-induced hypertension, stress-induced hypertension, angiotensin II-induced hyper- tension and aldosterone-induced hypertension. There are 2 types of central AT1R blockade, acute blockade and chronic blockade. The latter can be achieved by chemical blockade or genetic engineering. The present review article aimed to high- light the prevalence, functions, interactions and modulation means of central AT-1R in an effort to assist in the treatment of several pathological conditions. The identification of angiotensin-derived peptides and the development of AT-2R agonists may provide a wider perspective on RAS, as well as novel therapeutic strategies.
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Affiliation(s)
- Chuanxin Su
- Key Laboratory of Targeted Intervention of Cardiovascular Disease, Collaborative Innovation Center of Translational Medicine for Cardiovascular Disease, Department of Physiology, Nanjing Medical University, Nanjing, Jiangsu 211166, P.R. China
| | - Jinhua Xue
- Research Center for Cardiovascular and Cerebrovascular Diseases, The University of Duisburg‑Essen, Duisburg‑Essen University, D-45122 Essen, Germany
| | - Chao Ye
- Key Laboratory of Targeted Intervention of Cardiovascular Disease, Collaborative Innovation Center of Translational Medicine for Cardiovascular Disease, Department of Physiology, Nanjing Medical University, Nanjing, Jiangsu 211166, P.R. China
| | - Aidong Chen
- Key Laboratory of Targeted Intervention of Cardiovascular Disease, Collaborative Innovation Center of Translational Medicine for Cardiovascular Disease, Department of Physiology, Nanjing Medical University, Nanjing, Jiangsu 211166, P.R. China
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7
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Farmer GE, Amune A, Bachelor ME, Duong P, Yuan JP, Cunningham JT. Sniffer cells for the detection of neural Angiotensin II in vitro. Sci Rep 2019; 9:8820. [PMID: 31217439 PMCID: PMC6584535 DOI: 10.1038/s41598-019-45262-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 06/04/2019] [Indexed: 12/29/2022] Open
Abstract
Neuropeptide release in the brain has traditionally been difficult to observe. Existing methods lack temporal and spatial resolution that is consistent with the function and size of neurons. We use cultured "sniffer cells" to improve the temporal and spatial resolution of observing neuropeptide release. Sniffer cells were created by stably transfecting Chinese Hamster Ovary (CHO) cells with plasmids encoding the rat angiotensin type 1a receptor and a genetically encoded Ca2+ sensor. Isolated, cultured sniffer cells showed dose-dependent increases in fluorescence in response to exogenously applied angiotensin II and III, but not other common neurotransmitters. Sniffer cells placed on the median preoptic nucleus (a presumptive site of angiotensin release) displayed spontaneous activity and evoked responses to either electrical or optogenetic stimulation of the subfornical organ. Stable sniffer cell lines could be a viable method for detecting neuropeptide release in vitro, while still being able to distinguish differences in neuropeptide concentration.
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Affiliation(s)
- George E Farmer
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, United States
| | - Anna Amune
- Texas A&M University, College Station, TX, United States
| | - Martha E Bachelor
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, United States
| | - Phong Duong
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, United States
| | - Joseph P Yuan
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, United States
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, United States.
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8
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Shell B, Farmer GE, Nedungadi TP, Wang LA, Marciante AB, Snyder B, Cunningham RL, Cunningham JT. Angiotensin type 1a receptors in the median preoptic nucleus support intermittent hypoxia-induced hypertension. Am J Physiol Regul Integr Comp Physiol 2019; 316:R651-R665. [PMID: 30892911 PMCID: PMC6589598 DOI: 10.1152/ajpregu.00393.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 02/25/2019] [Accepted: 03/13/2019] [Indexed: 01/19/2023]
Abstract
Chronic intermittent hypoxia (CIH) is a model of the hypoxemia from sleep apnea that causes a sustained increase in blood pressure. Inhibition of the central renin-angiotensin system or FosB in the median preoptic nucleus (MnPO) prevents the sustained hypertensive response to CIH. We tested the hypothesis that angiotensin type 1a (AT1a) receptors in the MnPO, which are upregulated by CIH, contribute to this hypertension. In preliminary experiments, retrograde tract tracing studies showed AT1a receptor expression in MnPO neurons projecting to the paraventricular nucleus. Adult male rats were exposed to 7 days of intermittent hypoxia (cycling between 21% and 10% O2 every 6 min, 8 h/day during light phase). Seven days of CIH was associated with a FosB-dependent increase in AT1a receptor mRNA without changes in the permeability of the blood-brain barrier in the MnPO. Separate groups of rats were injected in the MnPO with an adeno-associated virus containing short hairpin (sh)RNA against AT1a receptors to test their role in intermittent hypoxia hypertension. Injections of shRNA against AT1a in MnPO blocked the increase in mRNA associated with CIH, prevented the sustained component of the hypertension during normoxia, and reduced circulating advanced oxidation protein products, an indicator of oxidative stress. Rats injected with shRNA against AT1a and exposed to CIH had less FosB staining in MnPO and the rostral ventrolateral medulla after intermittent hypoxia than rats injected with the control vector that were exposed to CIH. Our results indicate AT1a receptors in the MnPO contribute to the sustained blood pressure increase to intermittent hypoxia.
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MESH Headings
- Angiotensin II/administration & dosage
- Animals
- Blood Pressure/drug effects
- Disease Models, Animal
- Hypertension/etiology
- Hypertension/genetics
- Hypertension/metabolism
- Hypertension/physiopathology
- Hypoxia/complications
- Hypoxia/genetics
- Hypoxia/metabolism
- Hypoxia/physiopathology
- Injections, Intraventricular
- Male
- Oxidative Stress
- Preoptic Area/drug effects
- Preoptic Area/metabolism
- Preoptic Area/physiopathology
- Proto-Oncogene Proteins c-fos/genetics
- Proto-Oncogene Proteins c-fos/metabolism
- RNA Interference
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Rats, Sprague-Dawley
- Receptor, Angiotensin, Type 1/agonists
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/metabolism
- Signal Transduction
- Up-Regulation
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Affiliation(s)
- Brent Shell
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - George E Farmer
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - T Prashant Nedungadi
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Lei A Wang
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Alexandria B Marciante
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Brina Snyder
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Rebecca L Cunningham
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
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9
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Farmer GE, Balapattabi K, Bachelor ME, Little JT, Cunningham JT. AT 1a influences GABAA-mediated inhibition through regulation of KCC2 expression. Am J Physiol Regul Integr Comp Physiol 2018; 315:R972-R982. [PMID: 30156863 PMCID: PMC6295501 DOI: 10.1152/ajpregu.00105.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 08/27/2018] [Accepted: 08/27/2018] [Indexed: 11/22/2022]
Abstract
The median preoptic nucleus (MnPO) is an integrative site involved in body fluid homeostasis, cardiovascular control, thermoregulation, and sleep homeostasis. Angiotensin II (ANG II), a neuropeptide shown to have excitatory effects on MnPO neurons, is of particular interest with regard to its role in body fluid homeostasis and cardiovascular control. The present study investigated the role of angiotensin type 1a (AT1a) receptor activation on neuronal excitability in the MnPO. Male Sprague-Dawley rats were infused with an adeno-associated virus with an shRNA against the AT1a receptor or a scrambled control. In vitro loose-patch voltage-clamp recordings of spontaneous action potential activity were made from labeled MnPO neurons in response to brief focal application of ANG II or the GABAA receptor agonist muscimol. Additionally, tissue punches from MnPO were taken to asses mRNA and protein expression. AT1a receptor knockdown neurons were insensitive to ANG II and showed a marked reduction in GABAA-mediated inhibition. The reduction in GABAA-mediated inhibition was not associated with reductions in mRNA or protein expression of GABAA β-subunits. Knockdown of the AT1a receptor was associated with a reduction in the potassium-chloride cotransporter KCC2 mRNA as well as a reduction in pS940 KCC2 protein. The impaired GABAA-mediated inhibition in AT1a knockdown neurons was recovered by bath application of phospholipase C and protein kinase C activators. The following study indicates that AT1a receptor activation mediates the excitability of MnPO neurons, in part, through the regulation of KCC2. The regulation of KCC2 influences the intracellular [Cl-] and the subsequent efficacy of GABAA-mediated currents.
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Affiliation(s)
- George E Farmer
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth , Fort Worth, Texas
| | - Kirthikaa Balapattabi
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth , Fort Worth, Texas
| | - Martha E Bachelor
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth , Fort Worth, Texas
| | - Joel T Little
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth , Fort Worth, Texas
| | - J Thomas Cunningham
- Department of Physiology and Anatomy, University of North Texas Health Science Center at Fort Worth , Fort Worth, Texas
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10
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Pandey KN. Molecular and genetic aspects of guanylyl cyclase natriuretic peptide receptor-A in regulation of blood pressure and renal function. Physiol Genomics 2018; 50:913-928. [PMID: 30169131 DOI: 10.1152/physiolgenomics.00083.2018] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Natriuretic peptides (NPs) exert diverse effects on several biological and physiological systems, such as kidney function, neural and endocrine signaling, energy metabolism, and cardiovascular function, playing pivotal roles in the regulation of blood pressure (BP) and cardiac and vascular homeostasis. NPs are collectively known as anti-hypertensive hormones and their main functions are directed toward eliciting natriuretic/diuretic, vasorelaxant, anti-proliferative, anti-inflammatory, and anti-hypertrophic effects, thereby, regulating the fluid volume, BP, and renal and cardiovascular conditions. Interactions of NPs with their cognate receptors display a central role in all aspects of cellular, biochemical, and molecular mechanisms that govern physiology and pathophysiology of BP and cardiovascular events. Among the NPs atrial and brain natriuretic peptides (ANP and BNP) activate guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) and initiate intracellular signaling. The genetic disruption of Npr1 (encoding GC-A/NPRA) in mice exhibits high BP and hypertensive heart disease that is seen in untreated hypertensive subjects, including high BP and heart failure. There has been a surge of interest in the NPs and their receptors and a wealth of information have emerged in the last four decades, including molecular structure, signaling mechanisms, altered phenotypic characterization of transgenic and gene-targeted animal models, and genetic analyses in humans. The major goal of the present review is to emphasize and summarize the critical findings and recent discoveries regarding the molecular and genetic regulation of NPs, physiological metabolic functions, and the signaling of receptor GC-A/NPRA with emphasis on the BP regulation and renal and cardiovascular disorders.
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Affiliation(s)
- Kailash N Pandey
- Department of Physiology, Tulane University Health Sciences Center, School of Medicine , New Orleans, Louisiana
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11
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Mourão AA, de Mello ABS, Dos Santos Moreira MC, Rodrigues KL, Lopes PR, Xavier CH, Gomes RM, Freiria-Oliveira AH, Blanch GT, Colombari E, Pedrino GR. Median preoptic nucleus excitatory neurotransmitters in the maintenance of hypertensive state. Brain Res Bull 2018; 142:207-215. [PMID: 29944948 DOI: 10.1016/j.brainresbull.2018.06.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 06/19/2018] [Accepted: 06/21/2018] [Indexed: 12/18/2022]
Abstract
The crucial role of the median preoptic nucleus (MnPO) in the maintenance of hydroelectrolytic balance and autonomic regulation have been highlighted. Recently, the participation of the MnPO in the control of sympathetic nerve activity was demonstrated in essential hypertension model. However, peculiarities on the neurochemical changes underlying the differential role of MnPO during hypertension remain to be clarified. Therefore, this study aimed to investigate the main excitatory pathways that modulate MnPO neurons in hypertensive rats. Spontaneously hypertensive rats (SHR) and rats submitted previously to the Goldblatt protocol (two kidneys; one clip; 2K1C) were used. Rats of both groups (250 to 350 g, n = 6) were anesthetized with urethane (1.2 g/kg,i.v.) and instrumented to record mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA). Nanoinjection (100 nl) of saline (NaCl, 150 mM), losartan (AT1 receptor antagonist; 10 mM) and kynurenic acid (glutamate receptor antagonist; 50 mM) into the MnPO were performed. In 2K1C rats, glutamatergic blockade promoted decreases in MAP and RSNA (-19.1 ± 0.9 mmHg, -21.6 ± 2.8%, p < 0.05) when compared to saline (-0.4 ± 0.6 mmHg, 0.2 ± 0.7%, p < 0.05). Angiotensinergic inhibition also reduced these parameters (-11.5 ± 1.2 mmHg, -10.5 ± 1.0%, p < 0.05) in 2K1C. In SHR, Kynurenic acid nanoinjections produced hypotension and sympathoinhibition (-21.0 ± 2.5 mmHg, -24.7 ± 2.4%, p < 0.05), as well losartan nanoinjections (-9.7 ± 1.2 mmHg; p < 0.05) and RSNA (-12.0 ± 2.4%, p < 0.05). These findings support the conclusion that a tonic excitatory neurotransmission exerted by angiotensin II, and mostly by glutamate in the MnPO could participate in the modulation of blood pressure and RSNA independent on whether hypertension is primarily neurogenic or is secondary to stenosis in renal artery.
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Affiliation(s)
- Aline A Mourão
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - Aryanne B Soares de Mello
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - Marina C Dos Santos Moreira
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - Karla L Rodrigues
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - Paulo R Lopes
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - Carlos H Xavier
- Laboratory of Cardiovascular Physiology and Therapeutics, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - Rodrigo M Gomes
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - André H Freiria-Oliveira
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil
| | - Graziela T Blanch
- School of Medicine, Pharmacy and Biomedicine, Pontifical Catholic University of Goias, Goiania, GO, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University, Araraquara, São Paulo, Brazil
| | - Gustavo R Pedrino
- Center for Neuroscience and Cardiovascular Research, Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiania, GO, Brazil.
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12
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Angiotensin II facilitates GABAergic neurotransmission at postsynaptic sites in rat amygdala neurons. Neuropharmacology 2018; 133:334-344. [PMID: 29447844 DOI: 10.1016/j.neuropharm.2018.02.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 02/08/2018] [Accepted: 02/10/2018] [Indexed: 12/27/2022]
Abstract
The central nucleus of the amygdala (CeA) is critical in the regulation of sodium appetite. Angiotensin II (Ang II) is important in the generation of sodium appetite and may function as a neurotransmitter or modulator to affect the synaptic transmission and the excitability of neurons. However, the role of Ang II in the CeA remains unclear. In this study, we determined the effects of Ang II on the excitatory and inhibitory synaptic inputs to the CeA neurons in brain slices with whole-cell patch-clamp recordings. Ang II (0.5-5 μM) significantly potentiated the amplitude of spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) in a concentration-dependent manner. Ang II (2 μM) significantly increased the amplitude of miniature GABAergic inhibitory postsynaptic currents (mIPSCs) without affecting the frequency. This effect was blocked by Ang II type 1 (AT1) receptor antagonist, losartan. One mM guanosine 5'-O-(-2-thiodiphosphate) (GDP-β-s) in the pipette internal solution eliminated the facilitatory effect of Ang II on GABAergic synaptic transmission. In contrast, Ang II had no effect on the spontaneous glutamatergic excitatory postsynaptic currents (EPSCs) and did not alter the frequency and amplitude of miniature EPSCs at concentrations that facilitated IPSCs. Furthermore, Ang II decreased the firing activity of CeA neurons, and this effect was abolished by losartan and GDP-β-s. In addition, Ang II failed to inhibit CeA neurons in the presence of bicuculline. These data provide substantial new evidence that Ang II inhibits the CeA neurons by facilitation of GABAergic synaptic input efficacy through activation of postsynaptic AT1 receptors.
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Hu B, Qiao H, Sun B, Jia R, Fan Y, Wang N, Lu B, Yan JQ. AT1 receptor blockade in the central nucleus of the amygdala attenuates the effects of muscimol on sodium and water intake. Neuroscience 2015; 307:302-10. [PMID: 26344240 DOI: 10.1016/j.neuroscience.2015.08.069] [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: 07/31/2015] [Revised: 08/27/2015] [Accepted: 08/30/2015] [Indexed: 10/23/2022]
Abstract
The blockade of the central nucleus of the amygdala (CeA) with the GABAA receptor agonist muscimol significantly reduces hypertonic NaCl and water intake by sodium-depleted rats. In the present study we investigated the effects of previous injection of losartan, an angiotensin II type-1 (AT1) receptor antagonist, into the CeA on 0.3M NaCl and water intake reduced by muscimol bilaterally injected into the same areas in rats submitted to water deprivation-partial rehydration (WD-PR) and in rats treated with the diuretic furosemide (FURO). Male Sprague-Dawley rats with stainless steel cannulas bilaterally implanted into the CeA were used. Bilateral injections of muscimol (0.2 nmol/0.5 μl, n=8 rats/group) into the CeA in WD-PR-treated rats reduced 0.3M NaCl intake and water intake, and pre-treatment of the CeA with losartan (50 μg/0.5 μl) reversed the inhibitory effect of muscimol. The negative effect of muscimol on sodium and water intake could also be blocked by pretreatment with losartan microinjected into the CeA in rats given FURO (n=8 rats/group). However, bilateral injections of losartan (50 μg/0.5 μl) alone into the CeA did not affect the NaCl or water intake. These results suggest that the deactivation of CeA facilitatory mechanisms by muscimol injection into the CeA is promoted by endogenous angiotensin II acting on AT1 receptors in the CeA, which prevents rats from ingesting large amounts of hypertonic NaCl and water.
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Affiliation(s)
- B Hu
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China; Department of Prosthodontics, Xi'an Jiaotong University, College of Stomatology, 98# Xiwu Road, Xi'an, Shaanxi 710004, PR China
| | - H Qiao
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - B Sun
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - R Jia
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - Y Fan
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - N Wang
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - B Lu
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - J Q Yan
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University, Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China.
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Yan JB, Sun HL, Wang Q, Chen K, Sun B, Song L, Yan W, Zhao XL, Zhao SR, Zhang Y, Qiao H, Hu B, Yan JQ. Natriorexigenic effect of DAMGO is decreased by blocking AT1 receptors in the central nucleus of the amygdala. Neuroscience 2013; 262:9-20. [PMID: 24389419 DOI: 10.1016/j.neuroscience.2013.12.046] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 12/20/2013] [Accepted: 12/21/2013] [Indexed: 11/17/2022]
Abstract
μ-Opioid receptor (μ-OR) activation with agonist [D-Ala², N-Me-Phe⁴, Gly⁵-ol]-enkephalin (DAMGO) in the central nucleus of the amygdala (CeA) induces sodium (0.3M NaCl) intake in rats. The purpose of this study was to examine the effects of pre-injections of losartan (AT1 angiotensin receptor antagonist) into the CeA on 0.3 M NaCl and water intake induced by DAMGO injected bilaterally in the same area in rats submitted to water deprivation-partial rehydration (WD-PR) and in rats treated with the diuretic furosemide (FURO) combined with a low dose of the angiotensin-converting enzyme inhibitor captopril (CAP) injected subcutaneously (FURO/CAP). Male Sprague-Dawley rats with stainless steel cannulas implanted bilaterally into the CeA were used. In WD-PR rats, bilateral injections of DAMGO (2 nmol in 0.5 μL) into the CeA induced 0.3 M NaCl and water intake, and pre-treatment with losartan (108 nmol in 0.5 μL) injected into the CeA reduced 0.3 M NaCl and water intake induced by DAMGO. In FURO/CAP rats, pre-treatment with losartan (108 nmol in 0.5 μL) injected into the CeA attenuated the increase in 0.3M NaCl and water intake induced by DAMGO (2 nmol in 0.5 μL) injected into the same site. The results suggest that the natriorexigenic effect of DAMGO injected into the CeA is facilitated by endogenous angiotensin II acting on AT1 receptors in the CeA, which drives rats to ingest large amounts of hypertonic NaCl.
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Affiliation(s)
- J-B Yan
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China; Department of Physiology, Medical College of Henan University of Science and Technology, 263# Kaiyuan Avenue, Luoyang, Henan 471023, PR China
| | - H-L Sun
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China; Department of Oral Biology, Xi'an Jiaotong University College of Stomatology, 98# Xiwu Road, Xi'an, Shaanxi 710004, PR China
| | - Q Wang
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - K Chen
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - B Sun
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - L Song
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - W Yan
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - X-L Zhao
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - S-R Zhao
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - Y Zhang
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - H Qiao
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - B Hu
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China
| | - J-Q Yan
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, 76# West Yanta Road, Xi'an, Shaanxi 710061, PR China; Department of Oral Biology, Xi'an Jiaotong University College of Stomatology, 98# Xiwu Road, Xi'an, Shaanxi 710004, PR China.
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15
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O'Callaghan EL, Choong YT, Jancovski N, Allen AM. Central angiotensinergic mechanisms associated with hypertension. Auton Neurosci 2013; 175:85-92. [PMID: 23466041 DOI: 10.1016/j.autneu.2013.01.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 01/23/2013] [Accepted: 01/23/2013] [Indexed: 12/20/2022]
Abstract
Following its generation by both systemic and tissue-based renin-angiotensin systems, angiotensin II interacts with specific, G-protein coupled receptors to modulate multiple physiological systems, including the cardiovascular system. Genetic models in which the different components of the renin-angiotensin system have been deleted show large changes in resting blood pressure. Interruption of the generation of angiotensin II, or its interaction with these receptors, decreases blood pressure in hypertensive humans and experimental animal models of hypertension. Whilst the interaction of angiotensin II with the kidney is pivotal in this modulation of blood pressure, an involvement of the system in other tissues is important. Both systemic angiotensins, acting via the blood-brain barrier deficient circumventricular organs, and centrally-generated angiotensin modulate cardiovascular control by regulating fluid and electrolyte ingestion, autonomic activity and neuroendocrine function. This review discusses the pathways in the brain that are involved in this regulation of blood pressure as well as examining the sites in which altered angiotensin function might contribute to the development and maintenance of high blood pressure.
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Affiliation(s)
- Erin L O'Callaghan
- Department of Physiology, University of Melbourne, Vic., 3010, Australia
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Voisin AN, Drolet G, Mouginot D. Intrinsic properties of the sodium sensor neurons in the rat median preoptic nucleus. Am J Physiol Regul Integr Comp Physiol 2012; 303:R834-42. [PMID: 22874426 DOI: 10.1152/ajpregu.00260.2012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The essential role of the median preoptic nucleus (MnPO) in the integration of chemosensory information associated with the hydromineral state of the rat relies on the presence of a unique population of sodium (Na+) sensor neurons. Little is known about the intrinsic properties of these neurons; therefore, we used whole cell recordings in acute brain slices to determine the electrical fingerprints of this specific neural population of rat MnPO. The data collected from a large sample of neurons (115) indicated that the Na+ sensor neurons represent a majority of the MnPO neurons in situ (83%). These neurons displayed great diversity in both firing patterns induced by transient depolarizing current steps and rectifying properties activated by hyperpolarizing current steps. This diversity of electrical properties was also present in non-Na+ sensor neurons. Subpopulations of Na+ sensor neurons could be distinguished, however, from the non-Na+ sensor neurons. The firing frequency was higher in Na+ sensor neurons, showing irregular spike discharges, and the amplitude of the time-dependent rectification was weaker in the Na+ sensor neurons than in non-Na+ sensor neurons. The diversity among the electrical properties of the MnPO neurons contrasts with the relative function homogeneity (Na+ sensing). However, this diversity might be correlated with a variety of direct synaptic connections linking the MnPO to different brain areas involved in various aspects of the restoration and conservation of the body fluid homeostasis.
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Affiliation(s)
- Aurore N Voisin
- Axe Neurosciences du Centre de recherche du CHUQ, Université Laval, Québec, QC, Canada
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Hypothermia-induced hyperphosphorylation: a new model to study tau kinase inhibitors. Sci Rep 2012; 2:480. [PMID: 22761989 PMCID: PMC3386519 DOI: 10.1038/srep00480] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 06/13/2012] [Indexed: 12/22/2022] Open
Abstract
Tau hyperphosphorylation is one hallmark of Alzheimer's disease (AD) pathology. Pharmaceutical companies have thus developed kinase inhibitors aiming to reduce tau hyperphosphorylation. One obstacle in screening for tau kinase inhibitors is the low phosphorylation levels of AD-related phospho-epitopes in normal adult mice and cultured cells. We have shown that hypothermia induces tau hyperphosphorylation in vitro and in vivo. Here, we hypothesized that hypothermia could be used to assess tau kinase inhibitors efficacy. Hypothermia applied to models of biological gradual complexity such as neuronal-like cells, ex vivo brain slices and adult non-transgenic mice leads to tau hyperphosphorylation at multiple AD-related phospho-epitopes. We show that Glycogen Synthase Kinase-3 inhibitors LiCl and AR-A014418, as well as roscovitine, a cyclin-dependent kinase 5 inhibitor, decrease hypothermia-induced tau hyperphosphorylation, leading to different tau phosphorylation profiles. Therefore, we propose hypothermia-induced hyperphosphorylation as a reliable, fast, convenient and inexpensive tool to screen for tau kinase inhibitors.
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Natriorexigenic effect of baclofen is reduced by AT1 receptor blockade in the lateral parabrachial nucleus. Brain Res Bull 2011; 86:348-54. [DOI: 10.1016/j.brainresbull.2011.09.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 09/01/2011] [Accepted: 09/04/2011] [Indexed: 11/19/2022]
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Da Silva CZC, Menani JV, Callera JC. AT1 receptor blockade in the lateral parabrachial nucleus reduces the effects of muscimol on sodium intake. Brain Res 2011; 1403:28-36. [DOI: 10.1016/j.brainres.2011.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 05/30/2011] [Accepted: 06/02/2011] [Indexed: 11/29/2022]
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Johanson C, Stopa E, McMillan P, Roth D, Funk J, Krinke G. The distributional nexus of choroid plexus to cerebrospinal fluid, ependyma and brain: toxicologic/pathologic phenomena, periventricular destabilization, and lesion spread. Toxicol Pathol 2010; 39:186-212. [PMID: 21189316 DOI: 10.1177/0192623310394214] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Bordering the ventricular cerebrospinal fluid (CSF) are epithelial cells of choroid plexus (CP), ependyma and circumventricular organs (CVOs) that contain homeostatic transporters for mediating secretion/reabsorption. The distributional pathway ("nexus") of CP-CSF-ependyma-brain furnishes peptides, hormones, and micronutrients to periventricular regions. In disease/toxicity, this nexus becomes a conduit for infectious and xenobiotic agents. The sleeping sickness trypanosome (a protozoan) disrupts CP and downstream CSF-brain. Piperamide is anti-trypanosomic but distorts CP epithelial ultrastructure by engendering hydropic vacuoles; this reflects phospholipidosis and altered lysosomal metabolism. CP swelling by vacuolation may occlude CSF flow. Toxic drug tools delineate injuries to choroidal compartments: cyclophosphamide (vasculature), methylcellulose (interstitium), and piperazine (epithelium). Structurally perturbed CP allows solutes to penetrate the ventricles. There, CSF-borne pathogens and xenobiotics may permeate the ependyma to harm neurogenic stem cell niches. Amoscanate, an anti-helmintic, potently injures rodent ependyma. Ependymal/brain regions near CP are vulnerable to CSF-borne toxicants; this proximity factor links regional barrier breakdown to nearby periventricular pathology. Diverse diseases (e.g., African sleeping sickness, multiple sclerosis) take early root in choroidal, circumventricular, or perivascular loci. Toxicokinetics informs on pathogen, anti-parasitic agent, and auto-antibody distribution along the CSF nexus. CVOs are susceptible to plasma-borne toxicants/pathogens. Countering the physico-chemical and pathogenic insults to the homeostasis-mediating ventricle-bordering cells sustains brain health and fluid balance.
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Tremblay C, Berret E, Henry M, Nehmé B, Nadeau L, Mouginot D. Neuronal sodium leak channel is responsible for the detection of sodium in the rat median preoptic nucleus. J Neurophysiol 2010; 105:650-60. [PMID: 21084682 DOI: 10.1152/jn.00417.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sodium (Na(+)) ions are of primary importance for hydromineral and cardiovascular homeostasis, and the level of Na(+) in the body fluid compartments [plasma and cerebrospinal fluid (CSF)] is precisely monitored in the hypothalamus. Glial cells seem to play a critical role in the mechanism of Na(+) detection. However, the precise role of neurons in the detection of extracellular Na(+) concentration ([Na(+)](out)) remains unclear. Here we demonstrate that neurons of the median preoptic nucleus (MnPO), a structure in close contact with the CSF, are specific Na(+) sensors. Electrophysiological recordings were performed on dissociated rat MnPO neurons under isotonic [Na(+)] (100 mM NaCl) with local application of hypernatriuric (150, 180 mM NaCl) or hyponatriuric (50 mM NaCl) external solution. The hyper- and hyponatriuric conditions triggered an in- and an outward current, respectively. The reversal potential of the current matched the equilibrium potential of Na(+), indicating that a change in [Na(+)](out) modified the influx of Na(+) in the MnPO neurons. The conductance of the Na(+) current was not affected by either the membrane potential or the [Na(+)](out). Moreover, the channel was highly selective for lithium over guanidinium. Together, these data identified the channel as a Na(+) leak channel. A high correlation between the electrophysiological recordings and immunofluorescent labeling for the Na(X) channel in dissociated MnPO neurons strongly supports this channel as a candidate for the Na(+) leak channel responsible for the Na(+)-sensing ability of rat MnPO neurons. The absence of Na(X) labeling and of a specific current evoked by a change in [Na(+)](out) in mouse MnPO neurons suggests species specificity in the hypothalamus structures participating in central Na(+) detection.
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Affiliation(s)
- Christina Tremblay
- Centre de Recherche du CHUL, Département de Psychiatrie/Neurosciences, Université Laval, Québec, Canada
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