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Behuliak M, Bencze M, Boroš A, Vavřínová A, Vodička M, Ergang P, Vaněčková I, Zicha J. Chronic inhibition of angiotensin converting enzyme lowers blood pressure in spontaneously hypertensive rats by attenuation of sympathetic tone: The role of enhanced baroreflex sensitivity. Biomed Pharmacother 2024; 176:116796. [PMID: 38810397 DOI: 10.1016/j.biopha.2024.116796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 05/15/2024] [Accepted: 05/20/2024] [Indexed: 05/31/2024] Open
Abstract
Spontaneously hypertensive rats (SHR) are characterized by sympathetic hyperactivity and insufficient parasympathetic activity, and their high blood pressure (BP) can be lowered by long-term inhibition of the renin-angiotensin system. The aim of our study was to determine the influence of chronic inhibition of angiotensin converting enzyme (ACE) by captopril on cardiovascular regulation by the sympathetic and parasympathetic nervous system. Implanted radiotelemetric probes or arterial cannulas were used to measure mean arterial pressure (MAP), heart rate (HR), and arterial baroreflex in adult SHR and Wistar-Kyoto (WKY) rats under basal or stress conditions. MAP and the low-frequency component of systolic blood pressure variability (LF-SBPV, marker of sympathetic activity) were greater in SHR than in WKY rats. Under basal conditions chronic captopril treatment reduced both parameters more effectively in SHR, and the same was true during acute restraint stress. HR was similar in control rats of both strains, but WKY rats showed greater heart rate variability (HRV), indicating higher parasympathetic activity. Captopril administration increased HR in both strains, whereas HRV was decreased only in WKY. Chronic captopril treatment improved the impaired baroreflex-HR control in SHR by increasing the sensitivity but not the capacity of vagal arm of arterial baroreflex. Captopril treatment attenuated BP changes elicited by dimethylphenylpiperazinium (DMPP, agonist of nicotinic acetylcholine receptors), especially in SHR, indicating that sympathetic nerve transmission is facilitated by angiotensin II more in hypertensive than in normotensive animals. Thus, chronic ACE inhibition improves baroreflex sensitivity and lowers BP through both central and peripheral attenuation of sympathetic tone.
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Affiliation(s)
- Michal Behuliak
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Michal Bencze
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Almos Boroš
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Anna Vavřínová
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Vodička
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Peter Ergang
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Ivana Vaněčková
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Josef Zicha
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic.
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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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Huang H, Cheng H, Chia Y, Li Y, Van Minh H, Siddique S, Sukonthasarn A, Tay JC, Turana Y, Verma N, Kario K, Wang T. The role of renal nerve stimulation in percutaneous renal denervation for hypertension: A mini-review. J Clin Hypertens (Greenwich) 2022; 24:1187-1193. [PMID: 36196464 PMCID: PMC9532907 DOI: 10.1111/jch.14554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 07/11/2022] [Accepted: 07/18/2022] [Indexed: 11/19/2022]
Abstract
Recent trials have demonstrated the efficacy and safety of percutaneous renal sympathetic denervation (RDN) for blood pressure (BP)-lowering in patients with uncontrolled hypertension. Nevertheless, major challenges exist, such as the wide variation of BP-lowering responses following RDN (from strong response to no response) and lack of feasible and reproducible peri-procedural predictors for patient response. Both animal and human studies have demonstrated different patterns of BP responses following renal nerve stimulation (RNS), possibly related to varied regional proportions of sympathetic and parasympathetic nerve tissues along the renal arteries. Animal studies of RNS have shown that rapid electrical stimulation of the renal arteries caused renal artery vasoconstriction and increased norepinephrine secretion with a concomitant increase in BP, and the responses were attenuated after RDN. Moreover, selective RDN at sites with strong RNS-induced BP increases led to a more efficient BP-lowering effect. In human, when RNS was performed before and after RDN, blunted changes in RNS-induced BP responses were noted after RDN. The systolic BP response induced by RNS before RDN and blunted systolic BP response to RNS after RDN, at the site with maximal RNS-induced systolic BP response before RDN, both correlated with the 24-h ambulatory BP reductions 3-12 months following RDN. In summary, RNS-induced BP changes, before and after RDN, could be used to assess the immediate effect of RDN and predict BP reductions months following RDN. More comprehensive, large-scale and long term trials are needed to verify these findings.
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Affiliation(s)
- Hui‐Chun Huang
- Cardiovascular Center and Division of CardiologyDepartment of Internal MedicineNational Taiwan University HospitalNational Taiwan University College of MedicineTaipeiTaiwan
- Graduate Institute of Epidemiology and Preventive MedicineCollege of Public HealthNational Taiwan UniversityTaipeiTaiwan
| | - Hao‐min Cheng
- Department of MedicineTaipei Veterans General HospitalMedical Education and ResearchNational Yang‐Ming UniversityTaipeiTaiwan
| | - Yook‐Chin Chia
- Department of Medical SciencesSchool of Healthcare and Medical SciencesSunway UniversityBandar SunwayMalaysia
- Department of Primary Care MedicineFaculty of MedicineUniversity of MalayaKuala LumpurMalaysia
| | - Yan Li
- Department of Cardiovascular MedicineShanghai Institute of HypertensionShanghai Key Laboratory of HypertensionState Key Laboratory of Medical GenomicsNational Research Centre for Translational MedicineRuijin HospitalShanghai Jiaotong University School of MedicineShanghaiChina
| | - Huynh Van Minh
- Department of CardiologyUniversity of Medicine and PharmacyHue UniversityHue CityThua Thien‐HueVietnam
| | - Saulat Siddique
- Department of CardiologyFatima Memorial HospitalLahorePakistan
| | - Apichard Sukonthasarn
- Cardiology DivisionDepartment of Internal MedicineFaculty of MedicineChiang Mai UniversityChiang MaiThailand
| | - Jam Chin Tay
- Department of General MedicineTan Tock Seng HospitalSingaporeSingapore
| | - Yuda Turana
- Faculty of Medicine and Health SciencesAtma Jaya Catholic University of IndonesiaJakartaIndonesia
| | - Narsingh Verma
- Division of Cardiovascular MedicineDepartment of MedicineJichi Medical University School of MedicineShimotsukeTochigiJapan
| | - Kazuomi Kario
- Department of PhysiologyKing George's Medical UniversityLucknowIndia
| | - Tzung‐Dau Wang
- Cardiovascular Center and Division of CardiologyDepartment of Internal MedicineNational Taiwan University HospitalNational Taiwan University College of MedicineTaipeiTaiwan
- Division of Hospital MedicineDepartment of Internal MedicineNational Taiwan University HospitalNational Taiwan University College of MedicineTaipeiTaiwan
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Mannozzi J, Kim JK, Sala-Mercado JA, Al-Hassan MH, Lessanework B, Alvarez A, Massoud L, Bhatti T, Aoun K, O’Leary DS. Arterial Baroreflex Inhibits Muscle Metaboreflex Induced Increases in Effective Arterial Elastance: Implications for Ventricular-Vascular Coupling. Front Physiol 2022; 13:841076. [PMID: 35399256 PMCID: PMC8990766 DOI: 10.3389/fphys.2022.841076] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 02/18/2022] [Indexed: 01/19/2023] Open
Abstract
The ventricular-vascular relationship assesses the efficacy of energy transferred from the left ventricle to the systemic circulation and is quantified as the ratio of effective arterial elastance to maximal left ventricular elastance. This relationship is maintained during exercise via reflex increases in cardiovascular performance raising both arterial and ventricular elastance in parallel. These changes are, in part, due to reflexes engendered by activation of metabosensitive skeletal muscle afferents-termed the muscle metaboreflex. However, in heart failure, ventricular-vascular uncoupling is apparent and muscle metaboreflex activation worsens this relationship through enhanced systemic vasoconstriction markedly increasing effective arterial elastance which is unaccompanied by substantial increases in ventricular function. This enhanced arterial vasoconstriction is, in part, due to significant reductions in cardiac performance induced by heart failure causing over-stimulation of the metaboreflex due to under perfusion of active skeletal muscle, but also as a result of reduced baroreflex buffering of the muscle metaboreflex-induced peripheral sympatho-activation. To what extent the arterial baroreflex modifies the metaboreflex-induced changes in effective arterial elastance is unknown. We investigated in chronically instrumented conscious canines if removal of baroreflex input via sino-aortic baroreceptor denervation (SAD) would significantly enhance effective arterial elastance in normal animals and whether this would be amplified after induction of heart failure. We observed that effective arterial elastance (Ea), was significantly increased during muscle metaboreflex activation after SAD (0.4 ± 0.1 mmHg/mL to 1.4 ± 0.3 mmHg/mL). In heart failure, metaboreflex activation caused exaggerated increases in Ea and in this setting, SAD significantly increased the rise in Ea elicited by muscle metaboreflex activation (1.3 ± 0.3 mmHg/mL to 2.3 ± 0.3 mmHg/mL). Thus, we conclude that the arterial baroreflex does buffer muscle metaboreflex induced increases in Ea and this buffering likely has effects on the ventricular-vascular coupling.
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Abstract
Baroreceptors are mechanosensitive elements of the peripheral nervous system that maintain homeostasis by coordinating physiologic responses to external and internal stimuli. While it is recognized that carotid and cardiopulmonary baroreceptor reflexes modulate autonomic output to mitigate excessive fluctuations in arterial blood pressure and to maintain intravascular volume, increasing evidence suggests that baroreflex pathways also project to key regions of the central nervous system that regulate somatosensory, somatomotor, and central nervous system arousal. In addition to maintaining autonomic homeostasis, baroreceptor activity modulates the perception of pain, as well as neuroimmune, neuroendocrine, and cognitive responses to physical and psychologic stressors. This review summarizes the role that baroreceptor pathways play in modulating acute and chronic pain perception. The contribution of baroreceptor function to postoperative outcomes is also presented. Finally, methods that enhance baroreceptor function, which hold promise in improving postoperative and pain management outcomes, are presented.
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Takemoto Y. Muscle vasodilator response via potential adrenaline secretion to L-cysteine microinjected in rostral ventrolateral medulla of rats. Auton Neurosci 2020; 224:102644. [DOI: 10.1016/j.autneu.2020.102644] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/27/2020] [Accepted: 01/27/2020] [Indexed: 02/07/2023]
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Hendriks-Balk MC, Megdiche F, Pezzi L, Reynaud O, Da Costa S, Bueti D, Van De Ville D, Wuerzner G. Brainstem Correlates of a Cold Pressor Test Measured by Ultra-High Field fMRI. Front Neurosci 2020; 14:39. [PMID: 32082112 PMCID: PMC7005099 DOI: 10.3389/fnins.2020.00039] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 01/13/2020] [Indexed: 11/28/2022] Open
Abstract
Introduction Modern imaging techniques such as blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) allow the non-invasive and indirect measurement of brain activity. Whether changes in signal intensity can be detected in small brainstem regions during a cold pressor test (CPT) has not been explored thoroughly. The aim of this study was to measure whole brain and brainstem BOLD signal intensity changes in response to a modified CPT. Methods BOLD fMRI was measured in healthy normotensive participants during a randomized crossover study (modified CPT vs. control test) using ultra-high field 7 Tesla MRI scanner. Data were analyzed using Statistical Parametric Mapping (SPM) in a whole-brain approach, and with a brainstem-specific analysis using the spatially unbiased infra-tentorial template (SUIT) toolbox. Blood pressure (BP) and hormonal responses (norepinephrine and epinephrine levels) were also measured. Paired t-test statistics were used to compare conditions. Results Eleven participants (six women, mean age 28 ± 8.9 years) were analyzed. Mean arterial BP increased from 83 ± 12 mm Hg to 87 ± 12 mm Hg (p = 0.0009) during the CPT. Whole-brain analysis revealed significant activations linked to the CPT in the right supplementary motor cortex, midcingulate (bilateral) and the right anterior insular cortex. The brainstem-specific analysis showed significant activations in the dorsal medulla. Conclusion Changes in BOLD fMRI signal intensity in brainstem regions during a CPT can be detected, and show an increased response during a cold stress in healthy volunteers. Consequently, BOLD fMRI at 7T is a promising tool to explore and acquire new insights in the comprehension of neurogenic hypertension.
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Affiliation(s)
- Mariëlle C Hendriks-Balk
- Service of Nephrology and Hypertension, Department of Medicine, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Fatma Megdiche
- Service of Nephrology and Hypertension, Department of Medicine, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Laura Pezzi
- Service of Nephrology and Hypertension, Department of Medicine, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Olivier Reynaud
- Centre d'Imagerie BioMédicale (CIBM), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Sandra Da Costa
- Centre d'Imagerie BioMédicale (CIBM), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Domenica Bueti
- Centre d'Imagerie BioMédicale (CIBM), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Dimitri Van De Ville
- Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Medical Image Processing Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Grégoire Wuerzner
- Service of Nephrology and Hypertension, Department of Medicine, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
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Dalmasso C, Leachman JR, Osborn JL, Loria AS. Sensory signals mediating high blood pressure via sympathetic activation: role of adipose afferent reflex. Am J Physiol Regul Integr Comp Physiol 2019; 318:R379-R389. [PMID: 31868518 DOI: 10.1152/ajpregu.00079.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Blood pressure regulation in health and disease involves a balance between afferent and efferent signals from multiple organs and tissues. Although there are numerous reviews focused on the role of sympathetic nerves in different models of hypertension, few have revised the contribution of afferent nerves innervating adipose tissue and their role in the development of obesity-induced hypertension. Both clinical and basic research support the beneficial effects of bilateral renal denervation in lowering blood pressure. However, recent studies revealed that afferent signals from adipose tissue, in an adipose-brain-peripheral pathway, could contribute to the increased sympathetic activation and blood pressure during obesity. This review focuses on the role of adipose tissue afferent reflexes and briefly describes a number of other afferent reflexes modulating blood pressure. A comprehensive understanding of how multiple afferent reflexes contribute to the pathophysiology of essential and/or obesity-induced hypertension may provide significant insights into improving antihypertensive therapeutic approaches.
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Affiliation(s)
- Carolina Dalmasso
- Department of Pharmacology and Nutritional Sciences, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Jacqueline R Leachman
- Department of Pharmacology and Nutritional Sciences, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Jeffrey L Osborn
- Department of Biology, College of Arts and Sciences, University of Kentucky, Lexington, Kentucky
| | - Analia S Loria
- Department of Pharmacology and Nutritional Sciences, College of Medicine, University of Kentucky, Lexington, Kentucky
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Raimundo Fernades ÉM, de Moura SS, Silva RO, Totou NL, Baleeiro RDS, de Oliveira EC, Coelho DB, Cardoso LM, Becker LK. Acute volume expansion decreased baroreflex response after swimming but not after running exercise training in hypertensive rats. Clin Exp Hypertens 2019; 42:460-468. [DOI: 10.1080/10641963.2019.1693588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
| | - Samara Silva de Moura
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
| | | | - Nádia Lúcia Totou
- Research Center in Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | | | - Emerson Cruz de Oliveira
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
- Physical Education School, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Daniel Barbosa Coelho
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
- Physical Education School, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Leonardo Máximo Cardoso
- Research Center in Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Lenice Kappes Becker
- Postgraduate Program in Health and Nutrition/PPGSSN, Federal University of Ouro Preto, Ouro Preto, Brazil
- Physical Education School, Federal University of Ouro Preto, Ouro Preto, Brazil
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Barman SM. 2019 Ludwig Lecture: Rhythms in sympathetic nerve activity are a key to understanding neural control of the cardiovascular system. Am J Physiol Regul Integr Comp Physiol 2019; 318:R191-R205. [PMID: 31664868 DOI: 10.1152/ajpregu.00298.2019] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This review is based on the Carl Ludwig Distinguished Lecture, presented at the 2019 Experimental Biology Meeting in Orlando, FL, and provides a snapshot of >40 years of work done in collaboration with the late Gerard L. Gebber and colleagues to highlight the importance of considering the rhythmic properties of sympathetic nerve activity (SNA) and brain stem neurons when studying the neural control of autonomic regulation. After first providing some basic information about rhythms, I describe the patterns and potential functions of rhythmic activity recorded from sympathetic nerves under various physiological conditions. I review the evidence that these rhythms reflect the properties of central sympathetic neural networks that include neurons in the caudal medullary raphe, caudal ventrolateral medulla, caudal ventrolateral pons, medullary lateral tegmental field, rostral dorsolateral pons, and rostral ventrolateral medulla. The role of these brain stem areas in mediating steady-state and reflex-induced changes in SNA and blood pressure is discussed. Despite the common appearance of rhythms in SNA, these oscillatory characteristics are often ignored; instead, it is common to simply quantify changes in the amount of SNA to make conclusions about the function of the sympathetic nervous system in mediating responses to a variety of stimuli. This review summarizes work that highlights the need to include an assessment of the changes in the frequency components of SNA in evaluating the cardiovascular responses to various manipulations as well as in determining the role of different brain regions in the neural control of the cardiovascular system.
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Affiliation(s)
- Susan M Barman
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
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11
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The brainstem network controlling blood pressure: an important role for pressor sites in the caudal medulla and cervical spinal cord. J Hypertens 2018. [PMID: 28650915 DOI: 10.1097/hjh.0000000000001427] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
: Although medullary control of blood pressure (BP) has been extensively studied, the contribution of critical regions, such as pressor sites in the caudal medulla and upper cervical spinal cord and the lateral tegmental field, remains controversial and underappreciated. A series of pressor sites caudal to the caudal ventrolateral medulla (CVLM), including the caudal pressor area (CPA) and medullocervical pressor area, play an important role in control of BP. Activation and inhibition of these sites elicits pressor and depressor responses, respectively. Basal sympathetic tone is provided principally by the medullary lateral tegmental field and rostral ventrolateral medulla (RVLM). RVLM presympathetic neurons, which project to and drive preganglionic sympathetic somata in the intermediolateral cell column, are powerfully regulated by neurons in CVLM via tonic and phasic inhibition. The current state of knowledge is summarized thus: rostrocaudally organized columns of pressor sites caudal to CVLM extend to the upper cervical spinal cord; CPA pressor responses are RVLM-dependent; CPA mediates pressor responses by (first) inhibiting RVLM-projecting inhibitory CVLM units and (second) activating RVLM-projecting excitatory CVLM units; the chemoreflex is CPA-dependent; the baroreflex is CPA-independent; pressor responses to raphe obscurus stimulation are CPA-dependent; and medullocervical pressor area pressor responses are RVLM-independent, likely mediated by direct projections to the intermediolateral cell column. In this review, we seek to underscore and characterize the critical role played by the caudal medulla and upper cervical spinal cord in BP regulation and highlight important gaps in knowledge in interactions between the caudal medulla and other regions controlling BP, which may prove critical in revealing central mechanisms underlying pathophysiology of, and pharmacotherapeutic targets for, hypertension.
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12
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Hoogerwaard AF, de Jong MR, Elvan A. Renal Nerve Stimulation as Procedural End Point for Renal Sympathetic Denervation. Curr Hypertens Rep 2018; 20:24. [PMID: 29556850 DOI: 10.1007/s11906-018-0821-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE OF REVIEW Renal sympathetic denervation (RDN) as treatment option for hypertension has a strong rationale; however, variable effects on blood pressure (BP) have been reported ranging from non-response to marked reductions in BP. The absence of a procedural end point for RDN is one of the potential factors associated with the variable response. Studies have suggested the use of renal nerve stimulation (RNS) to adequately address this issue. This review aims to provide an overview of the clinical and experimental data available regarding the effects of RNS in the setting of RDN. RECENT FINDINGS Animal studies have shown that high-frequency electrical stimulation of the sympathetic nerves in the adventitia of the renal arteries elicits an increase in BP and leads to an increased norepinephrine spillover as a marker of increased sympathetic activity and these effects of stimulation were attenuated or blunted after RDN. In a human feasibility study using RNS both before and after RDN, similar BP responses were observed. Moreover, in patients with resistant hypertension, RNS-induced changes in BP appeared to be correlated with 24-h BP response after RDN. These data suggest that RNS is a useful tool to identify renal sympathetic nerve fibers in patients with treatment-resistant hypertension undergoing RDN, and to predict the likely effectiveness of RDN treatments. In acute procedural settings both in animal and human models, RNS elicits increase in BP and HR before RDN and these effects are blunted after RDN. Up to now, there is preliminary evidence that the RNS-induced BP changes predict 24-h ABPM outcome at follow-up in patients with resistant hypertension. Of note, studies are small sized and results of large trials comparing conventional RDN to RNS-guided RDN are warranted.
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Affiliation(s)
- Annemiek F Hoogerwaard
- Department of Cardiology, Isala Hospital, Dr. Van Heesweg 2, 8025 AB, Zwolle, The Netherlands
| | - Mark R de Jong
- Department of Cardiology, Isala Hospital, Dr. Van Heesweg 2, 8025 AB, Zwolle, The Netherlands
| | - Arif Elvan
- Department of Cardiology, Isala Hospital, Dr. Van Heesweg 2, 8025 AB, Zwolle, The Netherlands.
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Fioretti AC, Ogihara CA, Cafarchio EM, Venancio DP, de Almeida RL, Antonio BB, Sato MA. Renal and femoral venous blood flows are regulated by different mechanisms dependent on α-adrenergic receptor subtypes and nitric oxide in anesthetized rats. Vascul Pharmacol 2017; 99:53-64. [DOI: 10.1016/j.vph.2017.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 09/25/2017] [Accepted: 09/30/2017] [Indexed: 02/07/2023]
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14
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Soares ER, Barbosa CM, Campagnole-Santos MJ, Santos RAS, Alzamora AC. Hypotensive effect induced by microinjection of Alamandine, a derivative of angiotensin-(1-7), into caudal ventrolateral medulla of 2K1C hypertensive rats. Peptides 2017; 96:67-75. [PMID: 28889964 DOI: 10.1016/j.peptides.2017.09.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 09/03/2017] [Accepted: 09/04/2017] [Indexed: 01/11/2023]
Abstract
In the present study we evaluated the cardiovascular effects produced by microinjection of the new component of the renin-angiotensin system, alamandine, into caudal ventrolateral medulla of urethane-anesthetized normotensive and hypertensive 2K1C rats. The participation of different angiotensin receptors in the effects of alamandine was also evaluated. Microinjection of angiotensin-(1-7) was used for comparison. The microinjection of 4, 40 and 140pmol of alamandine or angiotensin-(1-7) into caudal ventrolateral medulla induced similar hypotensive effects in Sham-operated rats. However, contrasting with angiotensin-(1-7), in 2K1C rats the MAP response to the highest dose of alamandine was similar to that observed with saline. The microinjection of A-779, a selective Mas receptor antagonist, blunted the angiotensin-(1-7) effects but did not block the hypotensive effect of alamandine in Sham or in 2K1C rats. However, microinjection of D-Pro7-angiotensin-(1-7), a Mas/MrgD receptor antagonist, blocked the hypotensive effect induced by both peptides. Furthermore, microinjection of PD123319, a putative AT2 receptor antagonist blocked the hypotensive effect of alamandine, but not of angiotensin-(1-7), in Sham and 2K1C rats. Microinjection of the AT1 receptor antagonist, losartan, did not alter the hypotensive effect of angiotensin-(1-7) or alamandine in both groups. These results provide new insights about the differential mechanisms participating in the central cardiovascular effects of alamandine and angiotensin-(1-7) in normotensive and 2K1C hypertensive rats.
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Affiliation(s)
- E R Soares
- Núcleo de Pesquisa em Ciências Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil; Instituto Nacional de Ciência e Tecnologia em Inovação Nanobiofarmacêutica, Brazil
| | - C M Barbosa
- Núcleo de Pesquisa em Ciências Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil; Instituto Nacional de Ciência e Tecnologia em Inovação Nanobiofarmacêutica, Brazil
| | - M J Campagnole-Santos
- Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil; Instituto Nacional de Ciência e Tecnologia em Inovação Nanobiofarmacêutica, Brazil
| | - R A S Santos
- Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil; Instituto Nacional de Ciência e Tecnologia em Inovação Nanobiofarmacêutica, Brazil.
| | - A C Alzamora
- Departamento de Ciências Biológicas, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil; Núcleo de Pesquisa em Ciências Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil; Instituto Nacional de Ciência e Tecnologia em Inovação Nanobiofarmacêutica, Brazil.
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15
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Dombrowski MD, Mueller PJ. Sedentary conditions and enhanced responses to GABA in the RVLM: role of the contralateral RVLM. Am J Physiol Regul Integr Comp Physiol 2017; 313:R158-R168. [PMID: 28490450 DOI: 10.1152/ajpregu.00366.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 05/08/2017] [Accepted: 05/08/2017] [Indexed: 02/07/2023]
Abstract
A sedentary lifestyle is a major risk factor for cardiovascular disease, and both conditions are associated with overactivity of the sympathetic nervous system. Ongoing discharge of sympathetic nerves is regulated by the rostral ventrolateral medulla (RVLM), which in turn is modulated by the primary excitatory and inhibitory neurotransmitters glutamate and γ-amino-butyric acid (GABA), respectively. We reported previously that sedentary conditions enhance GABAergic modulation of sympathoexcitation in the RVLM, despite overall increased sympathoexcitation. Thus the purpose of this study was to test the hypothesis that sedentary conditions increase responsiveness to GABA in RVLM. Male Sprague-Dawley rats performed either chronic wheeling running or remained sedentary for 12-15 wk. Animals were instrumented to perform RVLM microinjections under Inactin anesthesia while mean arterial pressure (MAP) and splanchnic sympathetic nerve activity (SSNA) were recorded. Unilateral microinjections of GABA (30 nl, 0.3-600 mM) into the RVLM produced dose-dependent decreases in MAP and SSNA; however, no group differences were observed. Inhibition of the contralateral RVLM (muscimol, 2 mM, 90 nl) caused decreases in MAP and SSNA that were not different between groups but enhanced decreases in SSNA to GABA in sedentary rats only. In sinoaortic denervated rats, GABA microinjections before or after inhibition of the contralateral RVLM caused decreases in MAP and SSNA that were not different between groups. Our results suggest that the contralateral RVLM plays an important role in buffering responses to inhibition of the ipsilateral RVLM under sedentary but not physically active conditions. Based on these studies and others, sedentary conditions appear to enhance both sympathoinhibitory and sympathoexcitatory mechanisms in the RVLM. Enhanced sympathoinhibition may act to reduce already elevated sympathetic nervous system activity following sedentary conditions.
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Affiliation(s)
- Maryetta D Dombrowski
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Patrick J Mueller
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
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16
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Ghali MG, Srinivasan VM, Hanna E, DeMonte F. Overt and Subclinical Baroreflex Dysfunction After Bilateral Carotid Body Tumor Resection: Pathophysiology, Diagnosis, and Implications for Management. World Neurosurg 2017; 101:559-567. [DOI: 10.1016/j.wneu.2017.02.073] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 02/13/2017] [Accepted: 02/15/2017] [Indexed: 11/25/2022]
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17
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Raphan T, Cohen B, Xiang Y, Yakushin SB. A Model of Blood Pressure, Heart Rate, and Vaso-Vagal Responses Produced by Vestibulo-Sympathetic Activation. Front Neurosci 2016; 10:96. [PMID: 27065779 PMCID: PMC4814511 DOI: 10.3389/fnins.2016.00096] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 02/26/2016] [Indexed: 12/17/2022] Open
Abstract
Blood Pressure (BP), comprised of recurrent systoles and diastoles, is controlled by central mechanisms to maintain blood flow. Periodic behavior of BP was modeled to study how peak amplitudes and frequencies of the systoles are modulated by vestibular activation. The model was implemented as a relaxation oscillator, driven by a central signal related to Desired BP. Relaxation oscillations were maintained by a second order system comprising two integrators and a threshold element in the feedback loop. The output signal related to BP was generated as a nonlinear function of the derivative of the first state variable, which is a summation of an input related to Desired BP, feedback from the states, and an input from the vestibular system into one of the feedback loops. This nonlinear function was structured to best simulate the shapes of systoles and diastoles, the relationship between BP and Heart Rate (HR) as well as the amplitude modulations of BP and Pulse Pressure. Increases in threshold in one of the feedback loops produced lower frequencies of HR, but generated large pulse pressures to maintain orthostasis, without generating a VasoVagal Response (VVR). Pulse pressures were considerably smaller in the anesthetized rats than during the simulations, but simulated pulse pressures were lowered by including saturation in the feedback loop. Stochastic changes in threshold maintained the compensatory Baroreflex Sensitivity. Sudden decreases in Desired BP elicited non-compensatory VVRs with smaller pulse pressures, consistent with experimental data. The model suggests that the Vestibular Sympathetic Reflex (VSR) modulates BP and HR of an oscillating system by manipulating parameters of the baroreflex feedback and the signals that maintain the oscillations. It also shows that a VVR is generated when the vestibular input triggers a marked reduction in Desired BP.
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Affiliation(s)
- Theodore Raphan
- Department of Computer and Information Science, Institute for Neural and Intelligent Systems, Brooklyn College, City University of New York New York, NY, USA
| | - Bernard Cohen
- Department of Neurology, Icahn School of Medicine at Mount Sinai New York, NY, USA
| | - Yongqing Xiang
- Department of Computer and Information Science, Institute for Neural and Intelligent Systems, Brooklyn College, City University of New York New York, NY, USA
| | - Sergei B Yakushin
- Department of Neurology, Icahn School of Medicine at Mount Sinai New York, NY, USA
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18
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Major Autonomic Neuroregulatory Pathways Underlying Short- and Long-Term Control of Cardiovascular Function. Curr Hypertens Rep 2016; 18:18. [DOI: 10.1007/s11906-016-0625-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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19
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SUN JIAN, SCHERLAG BENJAMINJ, HE BO, SHEN XIAOHUA, GAO MEI, ZHANG LING, LI YIGANG, PO SUNNYS. Electrical Stimulation of Vascular Autonomic Nerves: Effects on Heart Rate, Blood Pressure, and Arrhythmias. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2015; 38:825-30. [DOI: 10.1111/pace.12603] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 12/27/2014] [Accepted: 01/28/2015] [Indexed: 11/30/2022]
Affiliation(s)
- JIAN SUN
- Department of Cardiology; Xinhua Hospital; Shanghai Jiao Tong University School of Medicine; Shanghai China
| | | | - BO HE
- Heart Rhythm Institute, University of Oklahoma HSC; Oklahoma City Oklahoma
| | - XIAOHUA SHEN
- Heart Rhythm Institute, University of Oklahoma HSC; Oklahoma City Oklahoma
| | - MEI GAO
- Heart Rhythm Institute, University of Oklahoma HSC; Oklahoma City Oklahoma
| | - LING ZHANG
- Department of Cardiology; the First Affiliated Hospital of Xinjiang Medical University; Xinjiang China
| | - YIGANG LI
- Department of Cardiology; Xinhua Hospital; Shanghai Jiao Tong University School of Medicine; Shanghai China
| | - SUNNY S. PO
- Heart Rhythm Institute, University of Oklahoma HSC; Oklahoma City Oklahoma
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20
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Geraldes V, Goncalves-Rosa N, Liu B, Paton JF, Rocha I. Essential role of RVL medullary neuronal activity in the long term maintenance of hypertension in conscious SHR. Auton Neurosci 2014; 186:22-31. [DOI: 10.1016/j.autneu.2014.09.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 08/14/2014] [Accepted: 09/05/2014] [Indexed: 02/07/2023]
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21
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Takemoto Y. l-Cysteine and l-AP4 microinjections in the rat caudal ventrolateral medulla decrease arterial blood pressure. Auton Neurosci 2014; 186:45-53. [DOI: 10.1016/j.autneu.2014.09.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 09/12/2014] [Accepted: 09/21/2014] [Indexed: 02/07/2023]
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22
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Feng L, Uteshev VV. Projection target-specific action of nicotine in the caudal nucleus of the solitary tract. J Neurosci Res 2014; 92:1560-72. [PMID: 24975270 DOI: 10.1002/jnr.23436] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 05/11/2014] [Accepted: 05/20/2014] [Indexed: 01/26/2023]
Abstract
The brainstem nucleus of the solitary tract (NTS) is the key integrating relay in the central processing of sensory information from the thoracic and from most subdiaphragmatic viscera. Modulation of neuronal excitability and synaptic activity in the NTS by nicotinic agents can have potent effects on vital physiological functions, such as feeding, digestion, respiration, and blood circulation. Caudal NTS neurons demonstrate considerable heterogeneity in projection targets, synaptic properties, and expression of nicotinic acetylcholine receptors (nAChRs). However, despite its heterogeneity, the caudal NTS may contain discrete subsets of neurons with unique projection target-specific properties. To test this hypothesis, we used in vivo fluorescent tracing and ex vivo patch-clamp electrophysiology to evaluate responsiveness to nicotine of anatomically identified caudal NTS neurons that project to the hypothalamic paraventricular nucleus (PVN) and the brainstem caudal ventrolateral medulla (CVLM). The results of this study demonstrate that responsiveness to nicotine correlates with where the neurons project. Specifically, PVN-projecting caudal NTS neurons respond to nicotine only presynaptically (i.e., via activation of presynaptic nAChRs and potentiation of synaptic release of glutamate), suggesting indirect, glutamate-dependent effects of nicotine on the PVN-projecting NTS circuitry. By contrast, CVLM-projecting caudal NTS neurons exhibit only limited presynaptic, but dominant somatodendritic, responsiveness to nicotine, suggesting that the effects of nicotine on the CVLM-projecting NTS circuitry are direct and largely glutamate independent. Understanding the relationships among function-specific brainstem/hypothalamic neuronal networks, nuclei, and individual neurons could help develop therapies targeting identifiable neuronal circuits to offset impaired autonomic homeostasis.
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Affiliation(s)
- Lin Feng
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois
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23
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Ideguchi M, Kajiwara K, Yoshikawa K, Sadahiro H, Nomura S, Fujii M, Suzuki M. Characteristics of intraoperative abnormal hemodynamics during resection of an intra-fourth ventricular tumor located on the dorsal medulla oblongata. Neurol Med Chir (Tokyo) 2013; 53:655-62. [PMID: 24077276 PMCID: PMC4508747 DOI: 10.2176/nmc.oa2012-0401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Abnormal hemodynamics during extirpation of a para-medulla oblongata (MO) tumor is common and may be associated with direct vagal stimulation of the medullary circuit. However, resection of tumors on the dorsal MO may also induce hemodynamic instability without direct vagal stimulus. The objective of this study was to examine the characteristics of hemodynamic instability unrelated to vagal stimulus during dissection of an intra-fourth ventricular tumor with attachment to the dorsal MO. A retrospective analysis was performed in 13 patients. Abnormal hemodynamics were defined as a > 20% change from the means of the intraoperative mean arterial pressure (MAP) and heart rate (HR). Relationships of intraoperative hemodynamics were evaluated with various parameters, including the volume of the MO. Six patients (46.2%) had intraoperative hypertension during separation of the tumor bulk from the dorsal MO. The maximum MAP and HR in these patients were significantly greater than those in patients with normal hemodynamics (116.0 ± 18.0 mmHg versus 85.6 ± 6.5 mmHg; 124.3 ± 22.8 bpm versus 90.5 ± 14.7 bpm). All six cases with abnormal hemodynamics showed hemodynamic fluctuation during separation of the tumor bulk from the dorsal MO. The preoperative volume of the MO in these patients was 1.11 cc less than that in patients with normal hemodynamics, but the volume after tumor resection was similar in the two groups (5.23 cc and 5.12 cc). This suggests that the MO was compressed by the conglutinate tumor bulk, with resultant fluctuation of hemodynamics. Recognition of and preparation for this phenomenon are important for surgery on a tumor located on the dorsal MO.
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Affiliation(s)
- Makoto Ideguchi
- Department of Neurosurgery, Yamaguchi University Graduate School of Medicine
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24
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Totola L, Alves T, Takakura A, Ferreira-Neto H, Antunes V, Menani J, Colombari E, Moreira T. Commissural nucleus of the solitary tract regulates the antihypertensive effects elicited by moxonidine. Neuroscience 2013; 250:80-91. [DOI: 10.1016/j.neuroscience.2013.06.065] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 06/28/2013] [Indexed: 01/28/2023]
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25
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Crestani CC, Alves FH, Gomes FV, Resstel LB, Correa FM, Herman JP. Mechanisms in the bed nucleus of the stria terminalis involved in control of autonomic and neuroendocrine functions: a review. Curr Neuropharmacol 2013; 11:141-59. [PMID: 23997750 PMCID: PMC3637669 DOI: 10.2174/1570159x11311020002] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 11/21/2012] [Accepted: 12/03/2012] [Indexed: 12/22/2022] Open
Abstract
The bed nucleus of the stria terminalis (BNST) is a heterogeneous and complex limbic forebrain structure, which plays an important role in controlling autonomic, neuroendocrine and behavioral responses. The BNST is thought to serve as a key relay connecting limbic forebrain structures to hypothalamic and brainstem regions associated with autonomic and neuroendocrine functions. Its control of physiological and behavioral activity is mediated by local action of numerous neurotransmitters. In the present review we discuss the role of the BNST in control of both autonomic and neuroendocrine function. A description of BNST control of cardiovascular and hypothalamus-pituitary-adrenal axisactivity at rest and during physiological challenges (stress and physical exercise) is presented. Moreover, evidence for modulation of hypothalamic magnocellular neurons activity is also discussed. We attempt to focus on the discussion of BNST neurochemical mechanisms. Therefore, the source and targets of neurochemical inputs to BNST subregions and their role in control of autonomic and neuroendocrine function is discussed in details.
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Affiliation(s)
- Carlos C Crestani
- Laboratory of Pharmacology, Department of Natural Active Principles and Toxicology, School of Pharmaceutical Sciences, São Paulo State University, UNESP, Araraquara, SP, 14801-902, Brazil
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26
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Turner A, Kumar N, Farnham M, Lung M, Pilowsky P, McMullan S. Rostroventrolateral medulla neurons with commissural projections provide input to sympathetic premotor neurons: anatomical and functional evidence. Eur J Neurosci 2013; 38:2504-15. [PMID: 23651135 DOI: 10.1111/ejn.12232] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 03/21/2013] [Accepted: 03/27/2013] [Indexed: 01/09/2023]
Abstract
The activity of neurons in the rostral ventrolateral medulla (RVLM) is critical for the generation of vasomotor sympathetic tone. Multiple pre-sympathetic pathways converge on spinally projecting RVLM neurons, but the origin and circumstances in which such inputs are active are poorly understood. We have previously shown that input from the contralateral brainstem contributes to the baseline activity of this population: in the current study we investigate the distribution, phenotype and functional properties of RVLM neurons with commissural projections in the rat. We firstly used retrograde transport of fluorescent microspheres to identify neurons that project to the contralateral RVLM. Labelled neurons were prominent in a longitudinal column that extended over 1 mm caudal from the facial nucleus and contained hybridisation products indicating enkephalin (27%), GABA (15%) and adrenaline (3%) synthesis and included 6% of bulbospinal neurons identified by transport of cholera toxin B. Anterograde transport of fluorescent dextran-conjugate from the contralateral RVLM revealed extensive inputs throughout the RVLM that frequently terminated in close apposition with catecholaminergic and bulbospinal neurons. In urethane-anaesthetised rats we verified that 28/37 neurons antidromically activated by electrical stimulation of the contralateral pressor region were spontaneously active, of which 13 had activity locked to central respiratory drive and 15 displayed ongoing tonic discharge. In six tonically active neurons sympathoexcitatory roles were indicated by spike-triggered averages of splanchnic sympathetic nerve activity. We conclude that neurons in the RVLM project to the contralateral brainstem, form synapses with sympathetic premotor neurons, and have functional properties consistent with sympthoexcitatory function.
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Affiliation(s)
- Anita Turner
- Australian School of Advanced Medicine, Macquarie University, Sydney, NSW, 2109, Australia
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27
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Hott SC, Gomes FV, Fabri DRS, Reis DG, Crestani CC, Côrrea FMA, Resstel LBM. Both α1- and β1-adrenoceptors in the bed nucleus of the stria terminalis are involved in the expression of conditioned contextual fear. Br J Pharmacol 2013; 167:207-21. [PMID: 22506532 DOI: 10.1111/j.1476-5381.2012.01985.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The bed nucleus of the stria terminalis (BNST) is a limbic structure that is involved in the expression of conditioned contextual fear. Among the numerous neural inputs to the BNST, noradrenergic synaptic terminals are prominent and some evidence suggests an activation of this noradrenergic neurotransmission in the BNST during aversive situations. Here, we have investigated the involvement of the BNST noradrenergic system in the modulation of behavioural and autonomic responses induced by conditioned contextual fear in rats. EXPERIMENTAL APPROACH Male Wistar rats with cannulae bilaterally implanted into the BNST were submitted to a 10 min conditioning session (6 footshocks, 1.5 ma/ 3 s). Twenty-four hours later freezing and autonomic responses (mean arterial pressure, heart rate and cutaneous temperature) to the conditioning box were measured for 10 min. The adrenoceptor antagonists were administered 10 min before the re-exposure to the aversive context. KEY RESULTS L-propranolol, a non-selective β-adrenoceptor antagonist, and phentolamine, a non-selective α-adrenoceptor antagonist, reduced both freezing and autonomic responses induced by aversive context. Similar results were observed with CGP20712, a selective β(1) -adrenoceptor antagonist, and WB4101, a selective α(1) -antagonist, but not with ICI118,551, a selective β(2) -adrenoceptor antagonist or RX821002, a selective α(2) -antagonist. CONCLUSIONS AND IMPLICATIONS These findings support the idea that noradrenergic neurotransmission in the BNST via α(1) - and β(1) -adrenoceptors is involved in the expression of conditioned contextual fear.
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Affiliation(s)
- Sara C Hott
- Department of Pharmacology, School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
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28
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The functional role of PI3K in maintenance of blood pressure and baroreflex suppression in (mRen2)27 and mRen2.Lewis rat. J Cardiovasc Pharmacol 2012; 58:367-73. [PMID: 21697727 DOI: 10.1097/fjc.0b013e31822555ca] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathway in brain of spontaneously hypertensive rats, but not Wistar-Kyoto (WKY) rats, contributes to elevated mean arterial pressure (MAP). The role of PI3K in the regulation of blood pressure or autonomic function in the nucleus tractus solitarii (NTS) is yet to be established in other Ang II-dependent models of hypertension. Thus, we microinjected PI3K inhibitors, wortmannin or LY294002, into the NTS, and measured MAP, baroreflex sensitivity (BRS) for heart rate (HR) control, and HR variability (HRV) in mRen2.Lewis congenic and (mRen2)27 transgenic rats. Bilateral NTS microinjections of wortmannin (100 nmol/L; 50 nL) reduced MAP in (mRen2)27 and mRen2.Lewis rats (33 ± 5 mm Hg, n = 7, and 32 ± 6 mm Hg, n = 9, respectively) for approximately 90 minutes. Spectral and sequence analysis showed improvements in spontaneous BRS and HRV (50%-100%) after treatment in both hypertensive strains. Injections of wortmannin into NTS of Hannover Sprague-Dawley or Lewis control rats failed to alter MAP, BRS, or HRV. In mRen2.Lewis, but not in control Lewis rats, LY294002 (50 μmole/L) reduced MAP and increased BRS and HRV similar to wortmannin. Thus, the pharmacologic blockade of the PI3K signaling pathway in NTS reveals an important contribution to resting MAP and BRS in rats with overexpression of the Ren2 gene.
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Nitric oxide at the CVLM is involved in the attenuation of the reflex bradycardia in renovascular hypertensive rats. Nitric Oxide 2012; 26:118-25. [DOI: 10.1016/j.niox.2012.01.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 12/06/2011] [Accepted: 01/06/2012] [Indexed: 01/09/2023]
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30
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McMullan S, Pilowsky PM. Sympathetic premotor neurones project to and are influenced by neurones in the contralateral rostral ventrolateral medulla of the rat in vivo. Brain Res 2012; 1439:34-43. [PMID: 22264491 DOI: 10.1016/j.brainres.2011.12.058] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 12/08/2011] [Accepted: 12/28/2011] [Indexed: 02/07/2023]
Abstract
The tonic activity of bulbospinal neurones in the rostral ventrolateral medulla (RVLM) is thought to underlie basal sympathetic nerve activity. A key research objective is to delineate the mechanisms that contribute to the firing of these neurones. In the current study we investigate the hypothesis that inputs arising in the contralateral RVLM converge on barosensitive bulbospinal neurones and contribute to their discharge pattern. Extracellular recordings were made from 24 barosensitive bulbospinal neurones in urethane anaesthetised, vagotomised and artificially ventilated rats during activation (glutamate or D,L-homocysteic acid microinjection, 50 nl, 50mM, or monopolar electrical stimulation) or inhibition (microinjection of GABA receptor agonists muscimol or isoguvacine, 50 nl, 10mM) of the contralateral RVLM. Chemical RVLM activation strongly increased (10/17) or inhibited (6/17) the spontaneous activity of neurones recorded in the contralateral RVLM. Electrical RVLM stimulation evoked a combination of short latency (median 6 ms) inhibitory and longer latency (median 9.1 ms, P<0.01) excitatory orthodromic responses in contralateral sympathetic premotor neurones and in some cases evoked antidromic action potentials that collided with spontaneous spikes. RVLM inhibition increased the discharge rate of sympathetic premotor neurones in the contralateral brainstem by 21 ± 13% (P<0.05) and reduced the variability of unit firing by 37 ± 12% (n=5, p<0.05). These findings indicate that sympathetic premotor neurones receive inhibitory and excitatory input from the contralateral RVLM, that inhibitory inputs predominate under baseline conditions, and that a population of sympathetic premotor neurones project to the contralateral RVLM in addition to their spinal targets.
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Affiliation(s)
- Simon McMullan
- Australian School of Advanced Medicine, Macquarie University, NSW, Australia.
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31
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Kumagai H, Oshima N, Matsuura T, Iigaya K, Imai M, Onimaru H, Sakata K, Osaka M, Onami T, Takimoto C, Kamayachi T, Itoh H, Saruta T. Importance of rostral ventrolateral medulla neurons in determining efferent sympathetic nerve activity and blood pressure. Hypertens Res 2011; 35:132-41. [PMID: 22170390 PMCID: PMC3273996 DOI: 10.1038/hr.2011.208] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Accentuated sympathetic nerve activity (SNA) is a risk factor for cardiovascular events. In this review, we investigate our working hypothesis that potentiated activity of neurons in the rostral ventrolateral medulla (RVLM) is the primary cause of experimental and essential hypertension. Over the past decade, we have examined how RVLM neurons regulate peripheral SNA, how the sympathetic and renin-angiotensin systems are correlated and how the sympathetic system can be suppressed to prevent cardiovascular events in patients. Based on results of whole-cell patch-clamp studies, we report that angiotensin II (Ang II) potentiated the activity of RVLM neurons, a sympathetic nervous center, whereas Ang II receptor blocker (ARB) reduced RVLM activities. Our optical imaging demonstrated that a longitudinal rostrocaudal column, including the RVLM and the caudal end of ventrolateral medulla, acts as a sympathetic center. By organizing and analyzing these data, we hope to develop therapies for reducing SNA in our patients. Recently, 2-year depressor effects were obtained by a single procedure of renal nerve ablation in patients with essential hypertension. The ablation injured not only the efferent renal sympathetic nerves but also the afferent renal nerves and led to reduced activities of the hypothalamus, RVLM neurons and efferent systemic sympathetic nerves. These clinical results stress the importance of the RVLM neurons in blood pressure regulation. We expect renal nerve ablation to be an effective treatment for congestive heart failure and chronic kidney disease, such as diabetic nephropathy.
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Affiliation(s)
- Hiroo Kumagai
- Department of Nephrology, National Defense Medical College, Tokorozawa, Japan.
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Oshima N, Kumagai H, Iigaya K, Onimaru H, Kawai A, Nishida Y, Saruta T, Itoh H. Baro-excited neurons in the caudal ventrolateral medulla (CVLM) recorded using the whole-cell patch-clamp technique. Hypertens Res 2011; 35:500-6. [DOI: 10.1038/hr.2011.211] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Tjen-A-Looi SC, Hsiao AF, Longhurst JC. Central and peripheral mechanisms underlying gastric distention inhibitory reflex responses in hypercapnic-acidotic rats. Am J Physiol Heart Circ Physiol 2011; 300:H1003-12. [PMID: 21217073 PMCID: PMC3064299 DOI: 10.1152/ajpheart.01131.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 12/30/2010] [Indexed: 11/22/2022]
Abstract
We have observed that in chloralose-anesthetized animals, gastric distension (GD) typically increases blood pressure (BP) under normoxic normocapnic conditions. However, we recently noted repeatable decreases in BP and heart rate (HR) in hypercapnic-acidotic rats in response to GD. The neural pathways, central processing, and autonomic effector mechanisms involved in this cardiovascular reflex response are unknown. We hypothesized that GD-induced decrease in BP and HR reflex responses are mediated during both withdrawal of sympathetic tone and increased parasympathetic activity, involving the rostral (rVLM) and caudal ventrolateral medulla (cVLM) and the nucleus ambiguus (NA). Rats anesthetized with ketamine and xylazine or α-chloralose were ventilated and monitored for HR and BP changes. The extent of cardiovascular inhibition was related to the extent of hypercapnia and acidosis. Repeated GD with both anesthetics induced consistent falls in BP and HR. The hemodynamic inhibitory response was reduced after blockade of the celiac ganglia or the intraabdominal vagal nerves with lidocaine, suggesting that the decreased BP and HR responses were mediated by both sympathetic and parasympathetic afferents. Blockade of the NA decreased the bradycardia response. Microinjection of kainic acid into the cVLM reduced the inhibitory BP response, whereas depolarization blockade of the rVLM decreased both BP and HR inhibitory responses. Blockade of GABA(A) receptors in the rVLM also reduced the BP and HR reflex responses. Atropine methyl bromide completely blocked the reflex bradycardia, and atenolol blocked the negative chronotropic response. Finally, α(1)-adrenergic blockade with prazosin reversed the depressor. Thus, in the setting of hypercapnic-acidosis, a sympathoinhibitory cardiovascular response is mediated, in part, by splanchnic nerves and is processed through the rVLM and cVLM. Additionally, a vagal excitatory reflex, which involves the NA, facilitates the GD-induced decreases in BP and HR responses. Efferent chronotropic responses involve both increased parasympathetic and reduced sympathetic activity, whereas the decrease in BP is mediated by reduced α-adrenergic tone.
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Affiliation(s)
- Stephanie C Tjen-A-Looi
- Susan Samueli Center for Integrative Medicine, Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4075, USA.
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Alves F, Resstel L, Correa F, Crestani C. Bed nucleus of the stria terminalis α1- and α2-adrenoceptors differentially modulate the cardiovascular responses to exercise in rats. Neuroscience 2011; 177:74-83. [DOI: 10.1016/j.neuroscience.2011.01.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 12/01/2010] [Accepted: 01/03/2011] [Indexed: 02/01/2023]
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Cao WH, Madden CJ, Morrison SF. Inhibition of brown adipose tissue thermogenesis by neurons in the ventrolateral medulla and in the nucleus tractus solitarius. Am J Physiol Regul Integr Comp Physiol 2010; 299:R277-90. [PMID: 20410479 DOI: 10.1152/ajpregu.00039.2010] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Neurons in the ventrolateral medulla (VLM) and in the nucleus tractus solitarius (NTS) play important roles in the regulation of cardiovascular and other autonomic functions. In the present study, we demonstrate an inhibition of brown adipose tissue (BAT) thermogenesis evoked by activation of neurons in the VLM, as well as by neurons in the intermediate NTS, of chloralose/urethane-anesthetized, artificially ventilated rats. Activation of neurons in either rostral VLM or caudal VLM with N-methyl-d-aspartate (12 nmol) reversed the cold-evoked increase in BAT sympathetic nerve activity (SNA), BAT temperature, and end-expired CO(2). Disinhibition of neurons in either VLM or NTS with the GABA(A) receptor antagonist, bicuculline (30 pmol), reversed the increases in BAT SNA, BAT temperature, and end-expired CO(2) that were elicited 1) by cold defense; 2) during the febrile model of nanoinjection of prostaglandin E(2) into the medial preoptic area; 3) by activation of neurons in the dorsomedial hypothalamus or in the rostral raphe pallidus (rRPa); or 4) by the micro-opioid receptor agonist fentanyl. Combined, but not separate, inhibitions of neurons in the VLM and in the NTS, with the GABA(A) receptor agonist, muscimol (120 pmol/site), produced increases in BAT SNA, BAT temperature, and expired CO(2), which were reversed by nanoinjection of glycine (30 nmol) into the rRPa. These findings suggest that VLM and NTS contain neurons whose activation inhibits BAT thermogenesis, that these neurons receive GABAergic inputs that are active under these experimental conditions, and that neurons in both sites contribute to the tonic inhibition of sympathetic premotor neuronal activity in the rRPa that maintains a low level of BAT thermogenesis in normothermic conditions.
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Affiliation(s)
- Wei-Hua Cao
- Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, Oregon 97006, USA
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Cangussu LM, de Castro UGM, do Pilar Machado R, Silva ME, Ferreira PM, dos Santos RAS, Campagnole-Santos MJ, Alzamora AC. Angiotensin-(1-7) antagonist, A-779, microinjection into the caudal ventrolateral medulla of renovascular hypertensive rats restores baroreflex bradycardia. Peptides 2009; 30:1921-7. [PMID: 19577603 DOI: 10.1016/j.peptides.2009.06.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 06/24/2009] [Accepted: 06/24/2009] [Indexed: 12/17/2022]
Abstract
In the present study we evaluated the effect of caudal ventrolateral medulla (CVLM) microinjection of the main angiotensin (Ang) peptides, Ang II and Ang-(1-7), and their selective antagonists on baseline arterial pressure (AP) and on baroreceptor-mediated bradycardia in renovascular hypertensive rats (2K1C). Microinjection of Ang II and Ang-(1-7) into the CVLM of 2K1C rats produced similar decrease in AP as observed in Sham rats. In both Sham and 2K1C, the hypotensive effect of Ang II and Ang-(1-7) at the CVLM was blocked, for up to 30 min, by previous CVLM microinjection of the Ang II AT1 receptor antagonist, Losartan, and Ang-(1-7) Mas antagonist, A-779, respectively. As expected, the baroreflex bradycardia was lower in 2K1C in comparison to Sham rats. CVLM microinjection of A-779 improved the sensitivity of baroreflex bradycardia in 2K1C hypertensive rats. In contrast, Losartan had no effect on the baroreflex bradycardia in either 2K1C or Sham rats. These results suggest that Ang-(1-7) at the CVLM may contribute to the low sensitivity of the baroreflex control of heart rate in renovascular hypertensive rats.
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Affiliation(s)
- Luiza Michelle Cangussu
- Departamento de Ciências Biológicas, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
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Goodchild AK, Moon EA. Maps of cardiovascular and respiratory regions of rat ventral medulla: focus on the caudal medulla. J Chem Neuroanat 2009; 38:209-21. [PMID: 19549567 DOI: 10.1016/j.jchemneu.2009.06.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 06/13/2009] [Accepted: 06/15/2009] [Indexed: 02/07/2023]
Abstract
The ventral medulla oblongata is critical for cardiorespiratory regulation. Here we review previous literature relating to sites within the ventral medulla that have been identified as having a 'cardiovascular' or 'respiratory' function. Together with the maps generated here, of sites from which cardiovascular and respiratory responses were evoked by glutamate microinjection, specific 'cardiovascular' regions have been defined and delineated. Commonly investigated regions, including the vasopressor rostral ventrolateral medulla (RVLM) and vasodepressor caudal ventrolateral medulla (CVLM), or areas only described by others, such as the medullary cerebral vasodilator area, are included for completeness. Emphasis is given to the caudal medulla, where three pressor regions, the caudal pressor area (CPA), the intermediate pressor area (IPA) and the medullo-cervical pressor area (MCPA), caudal to the vasodepressor CVLM were defined in the original data provided. The IPA is most responsive under pentobarbitone rather than urethane anaesthesia clearly delineating it from both the rostrally located CPA and the caudally located MCPA. The description of these multiple pressor areas appears to clarify the confusion that surrounds the identification of the 'CPA'. Also noted is a vasopressor region adjacent to the vasodepressor CVLM. Apart from the well described ventral respiratory column, a region medial to the pre-Bötzinger is described, from which increases in both phrenic nerve frequency and amplitude were evoked. Limitations associated with the technique of glutamate microinjection to define functionally specific regions are discussed. Particular effort has been made to define and delineate the regions with respect to ventrally located anatomical landmarks rather than the commonly used ventral surface or dorsal landmarks such as the obex or calamus scriptorius that may vary with the brain orientation or histological processing. This should ensure that a region can easily be defined by all investigators. Study of defined regions will help expedite the identification of the role of the multiple cell groups with diverse neurotransmitter complements that exist even within each of the regions described, in coordinating the delivery of oxygenated blood to the tissues.
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Affiliation(s)
- Ann K Goodchild
- The Australian School of Advanced Medicine, Macquarie University, New South Wales, 2109, Australia.
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Bourassa EA, Sved AF, Speth RC. Angiotensin modulation of rostral ventrolateral medulla (RVLM) in cardiovascular regulation. Mol Cell Endocrinol 2009; 302:167-75. [PMID: 19027823 PMCID: PMC9686041 DOI: 10.1016/j.mce.2008.10.039] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 10/05/2008] [Accepted: 10/24/2008] [Indexed: 02/07/2023]
Abstract
The rostral ventrolateral medulla (RVLM) and the presympathetic bulbospinal neurons in this region play a critical role in cardiovascular regulation. However, there is ambiguity regarding the precise anatomical coordinates of the RVLM and much still needs to be learned regarding the regulation and neurochemistry of this region. This brief review discusses some of these issues and focuses on the role of angiotensin-mediated signaling in the RVLM in blood pressure regulation.
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Affiliation(s)
- Erick A. Bourassa
- Department of Pharmacology, School of Pharmacy, University of Mississippi, University, MS 38677
- Current address: Biological Sciences, Northwest Missouri State University, Maryville, MO 64468
| | - Alan F. Sved
- Department of Neuroscience and Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Robert C. Speth
- Department of Pharmacology, School of Pharmacy, University of Mississippi, University, MS 38677
- Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677
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Microinjection of angiotensin II in the caudal ventrolateral medulla induces hyperalgesia. Neuroscience 2008; 158:1301-10. [PMID: 19116162 DOI: 10.1016/j.neuroscience.2008.11.044] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 11/20/2008] [Accepted: 11/24/2008] [Indexed: 02/07/2023]
Abstract
Nociceptive transmission from the spinal cord is controlled by supraspinal pain modulating systems that include the caudal ventrolateral medulla (CVLM). The neuropeptide angiotensin II (Ang II) has multiple effects in the CNS and at the medulla oblongata. Here we evaluated the expression of angiotensin type 1 (AT(1)) receptors in spinally-projecting CVLM neurons, and tested the effect of direct application of exogenous Ang II in the CVLM on nociceptive behaviors. Although AT(1)-immunoreactive neurons occurred in the CVLM, only 3% of AT(1)-positive neurons were found to project to the dorsal horn, using double-immunodetection of the retrograde tracer cholera toxin subunit B. In behavioral studies, administration of Ang II (100 pmol) in the CVLM gave rise to hyperalgesia in both the tail-flick and formalin tests. This hyperalgesia was significantly attenuated by local administration of the AT(1) antagonist losartan. The present study demonstrates that Ang II can act on AT(1) receptors in the CVLM to modulate nociception. The effect on spinal nociceptive processing is likely indirect, since few AT(1)-expressing CVLM neurons were found to project to the spinal cord. The renin-angiotensin system may also play a role in other supraspinal areas implicated in pain modulation.
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Mandel DA, Schreihofer AM. Glutamatergic inputs to the CVLM independent of the NTS promote tonic inhibition of sympathetic vasomotor tone in rats. Am J Physiol Heart Circ Physiol 2008; 295:H1772-9. [PMID: 18757486 DOI: 10.1152/ajpheart.216.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
GABAergic neurons in the caudal ventrolateral medulla (CVLM) are driven by baroreceptor inputs relayed via the nucleus tractus solitarius (NTS), and they inhibit neurons in rostral ventrolateral medulla to reduce sympathetic nerve activity (SNA) and arterial pressure (AP). After arterial baroreceptor denervation or lesions of the NTS, inhibition of the CVLM continues to increase AP, suggesting additional inputs also tonically activate the CVLM. This study examined whether the NTS contributes to baroreceptor-independent drive to the CVLM and whether glutamate promotes baroreceptor- and NTS-independent activation of the CVLM to tonically reduce SNA. In addition, we evaluated whether altering central respiratory drive, a baroreceptor-independent regulator of CVLM neurons, influences glutamatergic inputs to the CVLM. Splanchnic SNA and AP were measured in chloralose-anesthetized, ventilated, paralyzed rats. The infusion of nitroprusside decreased AP below threshold for baroreceptor afferent firing (<50 mmHg) and increased SNA to 209+/-22% (P<0.05), but the subsequent inhibition of the NTS by microinjection of the GABA(A) agonist muscimol did not further increase SNA. In contrast, after inhibition of the NTS, blockade of glutamatergic inputs to CVLM by microinjection of kynurenate increased SNA (274+/-54%; P<0.05; n=7). In vagotomized rats with baroreceptors unloaded, inhibition of glutamatergic inputs to CVLM evoked a larger rise in SNA when central respiratory drive was increased (219+/-16% vs. 271+/-17%; n=5; P<0.05). These data suggest that baroreceptor inputs provide the major drive for the NTS-mediated excitation of the CVLM. Furthermore, glutamate tonically activates the CVLM to reduce SNA independent of the NTS, and this excitatory input appears to be affected by the strength of central respiratory drive.
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Affiliation(s)
- Daniel A Mandel
- Department of Physiology, Medical College of Georgia, Augusta, Georgia 30912-3000, USA
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Sartor DM, Verberne AJM. The sympathoinhibitory effects of systemic cholecystokinin are dependent on neurons in the caudal ventrolateral medulla in the rat. Am J Physiol Regul Integr Comp Physiol 2006; 291:R1390-8. [PMID: 16793934 DOI: 10.1152/ajpregu.00314.2006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The gastrointestinal hormone CCK inhibits a subset of presympathetic neurons in the rostroventrolateral medulla (RVLM) that may be responsible for driving the sympathetic vasomotor outflow to the gastrointestinal circulation. We tested the hypothesis that the central neurocircuitry of this novel sympathoinhibitory reflex involves a relay in the caudal ventrolateral medullary (CVLM) depressor area. Blood pressure and greater splanchnic sympathetic nerve discharge (SSND) or lumbar sympathetic nerve discharge (LSND) were monitored in anesthetised, paralyzed male Sprague-Dawley rats. The effects of phenylephrine (PE, 10 microg/kg iv; baroreflex activation), phenylbiguanide (PBG, 10 microg/kg iv; von Bezold-Jarisch reflex) and CCK (4 or 8 microg/kg iv) on SSND or LSND, were tested before and after bilateral injection of 50-100 nl of the GABAA agonist muscimol (1.75 mM; n=6, SSND; n=7, LSND) or the excitatory amino acid antagonist kynurenate (55 mM; n=7, SSND) into the CVLM. PE and PBG elicited splanchnic and lumbar sympathoinhibitory responses that were abolished by bilateral muscimol or kynurenate injection into the CVLM. Similarly, the inhibitory effect of CCK on SSND was abolished after neuronal inhibition within the CVLM. In contrast, CCK-evoked lumbar sympathoexcitation was accentuated following bilateral CVLM inhibition. In control experiments (n=7), these agents were injected outside the CVLM and had no effect on splanchnic sympathoinhibitory responses to PE, PBG, and CCK. In conclusion, neurons in the CVLM are necessary for the splanchnic but not lumbar sympathetic vasomotor reflex response to CCK. This strengthens the view that subpopulations of RVLM neurons supply sympathetic vasomotor outflow to specific vascular territories.
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Affiliation(s)
- D M Sartor
- University of Melbourne, Clinical Pharmacology and Therapeutics Unit, Dept. of Medicine, Austin Health, Heidelberg, Victoria 3084, Australia.
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Alzamora AC, Santos RAS, Campagnole-Santos MJ. Baroreflex modulation by angiotensins at the rat rostral and caudal ventrolateral medulla. Am J Physiol Regul Integr Comp Physiol 2006; 290:R1027-34. [PMID: 16306161 DOI: 10.1152/ajpregu.00852.2004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We determined the effect of microinjection of ANG-(1–7) and ANG II into two key regions of the medulla that control the circulation [rostral and caudal ventrolateral medulla (RVLM and CVLM, respectively)] on baroreflex control of heart rate (HR) in anesthetized rats. Reflex bradycardia and tachycardia were induced by increases and decreases in mean arterial pressure produced by intravenous phenylephrine and sodium nitroprusside, respectively. The pressor effects of ANG-(1–7) and ANG II (25 pmol) after RVLM microinjection (11 ± 0.8 and 10 ± 2 mmHg, respectively) were not accompanied by consistent changes in HR. In addition, RVLM microinjection of these angiotensin peptides did not alter the bradycardic or tachycardic component of the baroreflex. CVLM microinjections of ANG-(1–7) and ANG II produced hypotension (−11 ± 1.5 and −11 ± 1.9 mmHg, respectively) that was similarly not accompanied by significant changes in HR. However, CVLM microinjections of angiotensins induced differential changes in the baroreflex control of HR. ANG-(1–7) attenuated the baroreflex bradycardia (0.26 ± 0.06 ms/mmHg vs. 0.42 ± 0.08 ms/mmHg before treatment) and facilitated the baroreflex tachycardia (0.86 ± 0.19 ms/mmHg vs. 0.42 ± 0.10 ms/mmHg before treatment); ANG II produced the opposite effect, attenuating baroreflex tachycardia (0.09 ± 0.06 ms/mmHg vs. 0.31 ± 0.07 ms/mmHg before treatment) and facilitating the baroreflex bradycardia (0.67 ± 0.16 ms/mmHg vs. 0.41 ± 0.05 ms/mmHg before treatment). The modulatory effect of ANG II and ANG-(1–7) on baroreflex sensitivity was completely abolished by peripheral administration of methylatropine. These results suggest that ANG II and ANG-(1–7) at the CVLM produce a differential modulation of the baroreflex control of HR, probably through distinct effects on the parasympathetic drive to the heart.
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Affiliation(s)
- Andréia C Alzamora
- Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627-ICB, UFMG, 31270-901, Belo Horizonte, MG, Brasil
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Sato MA, Morrison SF, Lopes OU, Colombari E. Differentiated hemodynamic changes controlled by splanchnic nerve. Auton Neurosci 2006; 126-127:202-10. [PMID: 16567132 DOI: 10.1016/j.autneu.2006.01.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2005] [Accepted: 01/31/2006] [Indexed: 10/24/2022]
Abstract
The splanchnic (SPL) nerve is a postganglionic sympathetic nerve involved in the tonic regulation of the cardiovascular system. Electrical stimulation of this nerve produces mesenteric vasoconstriction and it has been assumed that vasodilatory responses are dependent on inhibition of the vasoconstrictor tone. Several different central stimuli have been shown to dilate the hindquarter vascular bed and constrict the mesenteric vascular bed. To determine whether vasodilatory and vasoconstrictor effects in different vascular beds are elicited by activation of different sympathetic nerves, we investigated the hemodynamic changes in hindquarter, mesenteric and renal vascular beds evoked by electrical stimulation of the SPL nerve. Stimulation of the intact or sectioned SPL nerve in chloralose-anesthetized, artificially ventilated rats evoked increases in the hindquarter vascular conductance and simultaneously decreased the mesenteric and renal vascular conductance. Intravenous (i.v.) administration of L-NAME prior to stimulation of the proximal end of the sectioned SPL nerve abolished the increase in hindquarter conductance, suggesting the involvement of nitric oxide in this response. In assessing the hemodynamic effects of tonic activity on the SPL nerves, no significant changes were observed after unilateral section of the SPL nerve, but bilateral section of the SPL nerves decreased hindquarter conductance and did not significantly change the mesenteric conductance simultaneously. No consistent response was observed in the renal vascular bed after unilateral and subsequent contralateral section of the SPL nerves. These findings demonstrate that electrical stimulation of the SPL nerve produces mesenteric vasoconstriction and simultaneous hindquarter vasodilatation, which is mediated by nitric oxide. Moreover, the present data suggest that SPL nerves may provide a tonic vasodilatory tone in the hindquarter vascular bed and simultaneously a vasoconstrictor tone in another, undetermined vascular bed.
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Affiliation(s)
- Monica Akemi Sato
- Department of Physiology, Faculdade de Medicina do ABC, Av. Principe de Gales, 821, Vila Príncipe de Gales, 09060-650 Santo Andre, SP, Brazil.
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Michikami D, Kamiya A, Kawada T, Inagaki M, Shishido T, Yamamoto K, Ariumi H, Iwase S, Sugenoya J, Sunagawa K, Sugimachi M. Short-term electroacupuncture at Zusanli resets the arterial baroreflex neural arc toward lower sympathetic nerve activity. Am J Physiol Heart Circ Physiol 2006; 291:H318-26. [PMID: 16501021 DOI: 10.1152/ajpheart.00975.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although electroacupuncture reduces sympathetic nerve activity (SNA) and arterial pressure (AP), the effects of electroacupuncture on the arterial baroreflex remain to be systematically analyzed. We investigated the effects of electroacupuncture of Zusanli on the arterial baroreflex using an equilibrium diagram comprised of neural and peripheral arcs. In anesthetized, vagotomized, and aortic-denervated rabbits, we isolated carotid sinuses and changed intra-carotid sinus pressure (CSP) from 40 to 160 mmHg in increments of 20 mmHg/min while recording cardiac SNA and AP. Electroacupuncture of Zusanli was applied with a pulse duration of 5 ms and a frequency of 1 Hz. An electric current 10 times the minimal threshold current required for visible muscle twitches was used and was determined to be 4.8 +/- 0.3 mA. Electroacupuncture for 8 min decreased SNA and AP (n = 6). It shifted the neural arc (i.e., CSP-SNA relationship) to lower SNA but did not affect the peripheral arc (i.e., SNA-AP relationship) (n = 8). SNA and AP at the closed-loop operating point, determined by the intersection of the neural and peripheral arcs, decreased from 100 +/- 4 to 80 +/- 9 arbitrary units and from 108 +/- 9 to 99 +/- 8 mmHg (each P < 0.005), respectively. Peroneal denervation eliminated the shift of neural arc by electroacupuncture (n = 6). Decreasing the pulse duration to <2.5 ms eliminated the effects of SNA and AP reduction. In conclusion, short-term electroacupuncture resets the neural arc to lower SNA, which moves the operating point toward lower AP and SNA under baroreflex closed-loop conditions.
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Affiliation(s)
- Daisaku Michikami
- Department of Cardiovascular Dynamics, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565, Japan.
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Pinho D, Sousa T, Morato M, Tavares I, Albino-Teixeira A. Lesion of the caudal ventrolateral medulla prevents the induction of hypertension by adenosine receptor blockade in rats. Brain Res 2006; 1073-1074:374-82. [PMID: 16457788 DOI: 10.1016/j.brainres.2005.12.098] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 12/20/2005] [Accepted: 12/27/2005] [Indexed: 02/04/2023]
Abstract
The continuous infusion for 7 days of the adenosine receptor antagonist 1,3-dipropyl-8-sulfophenylxanthine (DPSPX) causes a sustained hypertension in rats, with an enhancement of sympathetic neurotransmission and activation of the renin-angiotensin system. We studied the involvement of the caudal ventrolateral medulla in the establishment of this hypertensive model by evaluating the effect of local lesioning in blood pressure (BP). Male adult Wistar rats received stereotaxic injections of 0.3 mul of saline or quinolinic acid (QA; 180 mM) in the caudal ventrolateral medulla followed by abdominal implant of minipump for infusion of saline or DPSPX (90 microg(-1) kg(-1) h(-1)). BP was measured in conscious animals every 2 days for 12 days. The sustained increase of BP (22.1 mm Hg; P < 0.001) detected in rats infused with DPSPX was reverted (6.7 mm Hg; P > 0.05) from day six onwards in animals with lesion of the lateralmost part of caudal ventrolateral medulla (VLMlat). The present results suggest that the development of hypertension induced by adenosine receptor antagonist involves the participation of the VLMlat. They further add new data as to the functional complexity of this medullary area involved in a variety of functions such as cardiovascular, respiratory, motor and pain control.
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Affiliation(s)
- Dora Pinho
- Institute of Pharmacology and Therapeutics, Faculty of Medicine of Porto and IBMC, University of Porto, Alameda Prof. Hernani Monteiro, 4200-319 Porto, Portugal
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Moreira TS, Sato MA, Takakura ACT, Menani JV, Colombari E. Role of pressor mechanisms from the NTS and CVLM in control of arterial pressure. Am J Physiol Regul Integr Comp Physiol 2005; 289:R1416-25. [PMID: 16051722 DOI: 10.1152/ajpregu.00053.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present study, we investigated the effects of inhibition of the caudal ventrolateral medulla (CVLM) with the GABA(A) agonist muscimol combined with the blockade of glutamatergic mechanism in the nucleus of the solitary tract (NTS) with kynurenic acid (kyn) on mean arterial pressure (MAP), heart rate (HR), and regional vascular resistances. In male Holtzman rats anesthetized intravenously with urethane/chloralose, bilateral injections of muscimol (120 pmol) into the CVLM or bilateral injections of kyn (2.7 nmol) into the NTS alone increased MAP to 186 +/- 11 and to 142 +/- 6 mmHg, respectively, vs. control: 105 +/- 4 mmHg; HR to 407 +/- 15 and to 412 +/- 18 beats per minute (bpm), respectively, vs. control: 352 +/- 12 bpm; and renal, mesenteric and hindquarter vascular resistances. However, in rats with the CVLM bilaterally blocked by muscimol, additional injections of kyn into the NTS reduced MAP to 88 +/- 5 mmHg and mesenteric and hindquarter vascular resistances below control baseline levels. Moreover, in rats with the glutamatergic mechanisms of the NTS blocked by bilateral injections of kyn, additional injections of muscimol into the CVLM also reduced MAP to 92 +/- 2 mmHg and mesenteric and hindquarter vascular resistances below control baseline levels. Simultaneous blockade of NTS and CVLM did not modify the increase in HR but also abolished the increase in renal vascular resistance produced by each treatment alone. The results suggest that important pressor mechanisms arise from the NTS and CVLM to control vascular resistance and arterial pressure under the conditions of the present study.
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Affiliation(s)
- Thiago Santos Moreira
- Department of Physiology, Universidade Federal de São Paulo--Escola Paulista de Medicina, Rua Botucatu, São Paulo, SP, Brazil
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Wang J, Peng YJ, Zhu DN. Amino acids modulate the hypotensive effect of angiotensin-(1-7) at the caudal ventrolateral medulla in rats. ACTA ACUST UNITED AC 2005; 129:1-7. [PMID: 15927691 DOI: 10.1016/j.regpep.2004.12.031] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Revised: 12/24/2004] [Accepted: 12/30/2004] [Indexed: 11/18/2022]
Abstract
The present experiment was designed to investigate the possible involvement of glutamate and taurine in the depressor response produced by angiotensin (Ang)-(1-7) at the caudal ventrolateral medulla (CVLM) in rats anesthetized with urethane and alpha-chloralose. Microinjection of Ang-(1-7) into the CVLM elicited a depressor response which was partially blocked by nonselective glutamate receptors antagonist kynurenic acid, whereas selective Ang-(1-7) antagonist Ang779 produced a pressor response which was significantly attenuated by taurine receptors antagonist 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide. Release of glutamate and taurine in the CVLM was evaluated with microdialysis, and the contents of these amino acids were measured with high performance liquid chromatography-fluorescent detection. The depressor response to Ang-(1-7) was accompanied by an increased release of glutamate and a decrease of taurine at the CVLM, whereas the pressor response to Ang779 was associated with a decreased release of glutamate and an increase of taurine. These results suggest that Ang-(1-7) and its antagonist Ang779 modulate the release of glutamate and taurine at the CVLM, which in turn contributes at least in part to the blood pressure response to Ang-(1-7) and Ang779.
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Affiliation(s)
- Jin Wang
- Department of Physiology and Pathophysiology, Shanghai Medical College of Fudan University (The former Shanghai Medical University), Shanghai 200032, China
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Bealer SL, Metcalf CS. Increased dietary sodium enhances activation of neurons in the medullary cardiovascular pathway during acute sodium loading in the rat. Auton Neurosci 2005; 117:33-40. [PMID: 15620568 DOI: 10.1016/j.autneu.2004.10.005] [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] [Received: 05/10/2004] [Revised: 10/21/2004] [Accepted: 10/25/2004] [Indexed: 11/23/2022]
Abstract
Increased sodium ingestion diminishes baroreflex-induced bradycardia in animals during acute sodium loading. These experiments studied effects of high sodium diet on activation of central nervous system sites associated with baroreflex activation and cardiovascular responses to hypernatremia during systemic sodium administration. Fos-like (Fos-Li) protein immunoreactivity was measured to estimate activation of neurons in the medullary baroreflex pathway (nucleus tractus solitarius (NTS), caudal ventrolateral medulla (CVLM), and rostral ventrolateral medulla (RVLM)), and in the hypothalamic paraventricular (PVN) and supraoptic nuclei (SON) in male Sprague-Dawley rats consuming standard chow and either tap water (TAP) or isotonic saline (ISO) for 2-3 weeks. Fos-Li immunoreactivity in the PVN and SON was similar in rats consuming TAP and ISO infused with 0.6 M NaCl. However, there were significantly more Fos-Li positive cells in NTS and CVLM of animals consuming ISO and infused with 0.6 M NaCl than any other experimental group, while Fos-Li immunoreactivity was similar in the RVLM in all animals. In conclusion, these data demonstrate that activation of neurons in the NTS and CVLM was significantly enhanced by moderate sodium loading in animals consuming high dietary sodium. The increased basal activation of neurons in these medullary sites could account for decreased baroreflex-induced bradycardia observed during ingestion of a high salt diet and acute, moderate sodium loading.
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Affiliation(s)
- Steven L Bealer
- Department of Pharmacology and Toxicology, College of Pharmacy University of Utah, 30 South 2000 East Rm 201, Salt Lake City, UT 84112, United States.
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Silveira SA, Viana Lima NR, Haibara AS, Coimbra CC. The hypothalamic paraventricular nucleus and carotid receptors modulate hyperglycemia induced by hemorrhage. Brain Res 2003; 993:183-91. [PMID: 14642845 DOI: 10.1016/j.brainres.2003.09.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The aim of this study was to assess the role of cholinergic transmission in the paraventricular nucleus of the hypothalamus (PVN) and carotid body receptors in mediating a rise in plasma glucose levels in response to hemorrhagic hypotension in rats. Methylatropine (1x10(-9) mol) or 0.15 M NaCl (0.2 microl) was injected into the PVN of Wistar rats weighing 250-300 g bearing a chronic jugular catheter for blood sampling and hemorrhage (1.2 ml/100 g/2 min). Polyethylene cannulae (PE-10) were inserted into the left femoral artery for cardiovascular monitoring. In the other experimental protocol, hemorrhage was performed on rats submitted to bilateral carotid receptor denervation (H-CD). The results show that the hyperglycemic response to hemorrhage was decreased by either methylatropine (H-MA) treatment or bilateral carotid receptor denervation (10.3+/-0.4 mM, control, n=15 vs. 7.7+/-0.2 mM, H-MA, n=12, and 7.6+/-0.3 mM, H-CD, n=5, p<0.01). Furthermore, methylatropine did not affect the recovery of blood pressure after hemorrhage-induced hypotension, suggesting that the metabolic and pressor adjustments have different efferent pathways. Our data demonstrate that cholinergic input from the PVN and carotid receptors (chemo- and/or baroreceptors) might participate in the same neural pathway activated by hemorrhage-induced hypotension that produces hyperglycemia.
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Affiliation(s)
- Simonton Andrade Silveira
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, ICB-UFMG, 6627 Av. Antonio Carlos, 31270-901 Belo Horizonte, MG, Brazil
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