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Güemes A, Georgiou P. Review of the role of the nervous system in glucose homoeostasis and future perspectives towards the management of diabetes. Bioelectron Med 2018; 4:9. [PMID: 32232085 PMCID: PMC7098234 DOI: 10.1186/s42234-018-0009-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 06/10/2018] [Indexed: 12/16/2022] Open
Abstract
Diabetes is a disease caused by a breakdown in the glucose metabolic process resulting in abnormal blood glucose fluctuations. Traditionally, control has involved external insulin injection in response to elevated blood glucose to substitute the role of the beta cells in the pancreas which would otherwise perform this function in a healthy individual. The central nervous system (CNS), however, also plays a vital role in glucose homoeostasis through the control of pancreatic secretion and insulin sensitivity which could potentially be used as a pathway for enhancing glucose control. In this review, we present an overview of the brain regions, peripheral nerves and molecular mechanisms by which the CNS regulates glucose metabolism and the potential benefits of modulating them for diabetes management. Development of technologies to interface to the nervous system will soon become a reality through bioelectronic medicine and we present the emerging opportunities for the treatment of type 1 and type 2 diabetes.
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Affiliation(s)
- Amparo Güemes
- Centre for Bio-Inspired Technology, Department of Electrical and Electronic Engineering, Imperial College London, South Kensington Campus, London, UK
| | - Pantelis Georgiou
- Centre for Bio-Inspired Technology, Department of Electrical and Electronic Engineering, Imperial College London, South Kensington Campus, London, UK
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Osaka M. Sudden Cardiac Death from the Perspective of Nonlinear Dynamics. J NIPPON MED SCH 2018. [PMID: 29540640 DOI: 10.1272/jnms.2018_85-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
There are some reports that sympathetic nerve activity (SNA) shows a characteristic pattern a few hours before the onset of lethal ventricular arrhythmias. If so, it could be possible to predict sudden cardiac death a few hours in advance of its occurrence. Recently, we reported that a previously unidentified V-trough of SNA is a potential precursor of lethal cardiac events by examining 24-hour ambulatory electrocardiograms in which such an event was recorded by chance. In contrast, the chaotic nature of heart rate variability has been noted recently from the viewpoint of nonlinear dynamics. This study models the hemodynamics, consisting of heart rate, SNA, and blood pressure (BP), by modifying a known chaotic electrical circuit, the Chua circuit. A V-trough of the SNA appears when the resistive element between the SNA and BP in the circuit is increased, which corresponds to the impaired regulation of BP by the SNA. This finding is consistent with an acknowledged finding that a depressed baroreflex (a reflex of the BP by SNA) may trigger a lethal arrhythmia. This study indicates that a V-trough of the SNA is a possible precursor of sudden cardiac death on the basis of experimental and clinical findings as well as mathematical modeling.
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Affiliation(s)
- Motohisa Osaka
- Department of Basic Science, Nippon Veterinary and Life Science University
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Oyama Y, Iigaya K, Minoura Y, Okabe T, Izumizaki M, Onimaru H. An in vitro experimental model for analysis of central control of sympathetic nerve activity. J Physiol Sci 2017; 67:629-635. [PMID: 28601952 PMCID: PMC10717256 DOI: 10.1007/s12576-017-0549-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 06/05/2017] [Indexed: 10/19/2022]
Abstract
Newborn rat brainstem-spinal cord preparations are useful for in vitro analysis of various brainstem functions including respiratory activity. When studying the central control of sympathetic nerve activity (SNA), it is important to record peripheral outputs of the SNA. We developed an in vitro preparation in which neuronal connections between the cardiovascular center in the medulla and SNA peripheral outputs are preserved. Zero- to 1-day-old rats were deeply anesthetized with isoflurane, and the brainstem and spinal cord were isolated with a partial right thoracic cage to record sympathetic nerve discharge from the right thoracic sympathetic nerve trunk (T9-T11). SNA in this preparation was strongly modulated by inspiratory activity. Single-shot electrical stimulation of the ipsilateral rostral ventrolateral medulla (RVLM) induced a transient increase of SNA. Bath application of angiotensin II induced an increase of SNA, and local ipsilateral microinjection of angiotensin II to the RVLM induced a transient increase of SNA. This preparation allows analysis of the central control of the SNA in vitro.
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Affiliation(s)
- Yuji Oyama
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
- Division of Cardiology and Cardiac Catheterization Laboratories, Showa University Northern Yokohama Hospital, 35-1 Chigasaki-Chuo, Tsuzuki, Yokohama, Kanagawa, 224-8503, Japan
| | - Kamon Iigaya
- Department of Internal Medicine, Hiratsuka City Hospital, 1-19-1 Minamihara, Hiratsuka, Kanagawa, 254-0065, Japan
| | - Yoshino Minoura
- Division of Cardiology, Department of Medicine, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Toshitaka Okabe
- Division of Cardiology and Cardiac Catheterization Laboratories, Showa University Northern Yokohama Hospital, 35-1 Chigasaki-Chuo, Tsuzuki, Yokohama, Kanagawa, 224-8503, Japan
| | - Masahiko Izumizaki
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan.
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Iigaya K, Okazaki S, Minoura Y, Onimaru H. Interaction between novel oscillation within the ventromedial hypothalamus and the sympathetic nervous system. Neuroscience 2017; 343:213-221. [DOI: 10.1016/j.neuroscience.2016.11.048] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 11/11/2016] [Accepted: 11/30/2016] [Indexed: 10/20/2022]
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Queiroz ACC, Sousa JCS, Cavalli AAP, Silva ND, Costa LAR, Tobaldini E, Montano N, Silva GV, Ortega K, Mion D, Tinucci T, Forjaz CLM. Post-resistance exercise hemodynamic and autonomic responses: Comparison between normotensive and hypertensive men. Scand J Med Sci Sports 2014; 25:486-94. [DOI: 10.1111/sms.12280] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/28/2014] [Indexed: 01/04/2023]
Affiliation(s)
- A. C. C. Queiroz
- Exercise Hemodynamic Laboratory; School of Physical Education and Sport; University of São Paulo; São Paulo Brazil
| | - J. C. S. Sousa
- Exercise Hemodynamic Laboratory; School of Physical Education and Sport; University of São Paulo; São Paulo Brazil
| | - A. A. P. Cavalli
- Exercise Hemodynamic Laboratory; School of Physical Education and Sport; University of São Paulo; São Paulo Brazil
| | - N. D. Silva
- Exercise Hemodynamic Laboratory; School of Physical Education and Sport; University of São Paulo; São Paulo Brazil
| | - L. A. R. Costa
- Exercise Hemodynamic Laboratory; School of Physical Education and Sport; University of São Paulo; São Paulo Brazil
| | - E. Tobaldini
- Department of Biomedical and Clinical Sciences “L. Sacco”, Medicine and Physiopathology; L. Sacco Hospital; University of Milan; Milan Italy
| | - N. Montano
- Department of Biomedical and Clinical Sciences “L. Sacco”, Medicine and Physiopathology; L. Sacco Hospital; University of Milan; Milan Italy
| | - G. V. Silva
- Hypertension Unit; General Hospital; University of São Paulo; São Paulo Brazil
| | - K. Ortega
- Hypertension Unit; General Hospital; University of São Paulo; São Paulo Brazil
| | - D. Mion
- Hypertension Unit; General Hospital; University of São Paulo; São Paulo Brazil
| | - T. Tinucci
- Exercise Hemodynamic Laboratory; School of Physical Education and Sport; University of São Paulo; São Paulo Brazil
- Hypertension Unit; General Hospital; University of São Paulo; São Paulo Brazil
| | - C. L. M. Forjaz
- Exercise Hemodynamic Laboratory; School of Physical Education and Sport; University of São Paulo; São Paulo Brazil
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Kario K, Saito I, Kushiro T, Teramukai S, Mori Y, Hiramatsu K, Kobayashi F, Shimada K. Enhanced blood pressure-lowering effect of olmesartan in hypertensive patients with chronic kidney disease-associated sympathetic hyperactivity: HONEST study. J Clin Hypertens (Greenwich) 2013; 15:555-61. [PMID: 23889717 PMCID: PMC3884768 DOI: 10.1111/jch.12132] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 04/09/2013] [Accepted: 04/12/2013] [Indexed: 01/12/2023]
Abstract
To investigate the blood pressure (BP)-lowering effect of olmesartan in relation to chronic kidney disease (CKD)-associated sympathetic nerve activity, a subanalysis was performed using data from the first 16 weeks of the Home BP Measurement With Olmesartan-Naive Patients to Establish Standard Target Blood Pressure (HONEST) study, a prospective observational study of hypertensive patients. Essential hypertensive patients who took no antihypertensive agent at baseline were classified based on baseline morning home systolic BP (MHSBP) in quartiles. In each class, patients were further classified based on baseline morning home pulse rate (MHPR). A subgroup analysis in patients with/without chronic kidney disease (CKD) was performed. A total of 5458 patients (mean age, 63.0 years; 51.6% women) were included. In the 4th quartile of baseline MHSBP (≥165 mm Hg), patients with MHPR ≥70 beats per minute had a greater BP reduction (by 3.2 mm Hg) than those with MHPR <70 beats per minute after 16 weeks of olmesartan-based treatment (P=.0005). An even greater BP reduction (by 6.6 mm Hg) was observed in patients with CKD than in patients without CKD in this group (P=.0084). Olmesartan was more effective in hypertensive patients with high MHSBP and MHPR ≥70 beats per minute, especially in patients with CKD. Olmesartan may have enhanced BP-lowering effects by improving renal ischemia in hypertensive CKD patients with potential increased sympathetic nerve activity.
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Affiliation(s)
- Kazuomi Kario
- Division of Cardiovascular Medicine, Department of Medicine, Jichi Medical University School of Medicine, Shimotsuke, Japan.
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Kishi T, Hirooka Y, Sunagawa K. Sympathoinhibition caused by orally administered telmisartan through inhibition of the AT1 receptor in the rostral ventrolateral medulla of hypertensive rats. Hypertens Res 2012; 35:940-6. [DOI: 10.1038/hr.2012.63] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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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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Okano Y, Tamura K, Masuda S, Ozawa M, Tochikubo O, Umemura S. Effects of angiotensin II receptor blockers on the relationships between ambulatory blood pressure and anti-hypertensive effects, autonomic function, and health-related quality of life. Clin Exp Hypertens 2010; 31:680-9. [PMID: 20001460 DOI: 10.3109/10641960903407041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The aim of the present study was to examine the relationships between the anti-hypertensive effects, autonomic function, and health-related quality of life (HRQOL) following treatment of hypertensive subjects with angiotensin receptor blockers (ARBs) in hypertensives. Nineteen patients with hypertension were assigned randomly to daily treatment with ARBs. After 16 weeks of treatment, blood pressure (BP) and 24 h the ratio of low frequency to high frequency component (LF/HF), an index of sympathovagal balance were decreased by ARBs. The HRQOL scores improved during the study. In this study, ARB therapy was associated with an improvement in BP, autonomic function, and HRQOL.
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Affiliation(s)
- Yasuko Okano
- Department of Medical Science and Cardiorenal Medicine, Yokoham City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-Ku, Yokohama City, Japan.
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Osaka M, Watanabe E, Murata H, Fuwamoto Y, Nanba S, Sakai K, Katoh T. V-Shaped Trough in Autonomic Activity Is a Possible Precursor of Life-Threatening Cardiac Events. Circ J 2010; 74:1906-15. [DOI: 10.1253/circj.cj-09-0935] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Motohisa Osaka
- Department of Basic Science, Nippon Veterinary and Life Science University
| | - Eiichi Watanabe
- Department of Cardiology, Fujita Health University School of Medicine
| | | | | | | | | | - Takao Katoh
- Department of Medicine, Nippon Medical School
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Ieda M, Fukuda K. Cardiac innervation and sudden cardiac death. Curr Cardiol Rev 2009; 5:289-95. [PMID: 21037846 PMCID: PMC2842961 DOI: 10.2174/157340309789317904] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 02/28/2009] [Accepted: 03/10/2009] [Indexed: 01/30/2023] Open
Abstract
The heart is extensively innervated and its performance is tightly controlled by the nervous system. Cardiac innervation density varies in diseased hearts leading to unbalanced neural activation and lethal arrhythmia. Diabetic sensory neuropathy causes silent myocardial ischemia, characterized by loss of pain perception during myocardial ischemia, which is a major cause of sudden cardiac death in diabetes mellitus (DM). Despite its clinical importance, the mechanisms underlying the control and regulation of cardiac innervation remain poorly understood.We found that cardiac innervation is determined by the balance between neural chemoattractants and chemorepellents within the heart. Nerve growth factor (NGF), a potent chemoattractant, is induced by endothelin-1 upregulation during development and is highly expressed in cardiomyocytes. By comparison, Sema3a, a neural chemorepellent, is highly expressed in the subendocardium of early stage embryos, and is suppressed during development. The balance of expression between NGF and Seme3a leads to epicardial-to-endocardial transmural sympathetic innervation patterning. We also found that downregulation of cardiac NGF leads to diabetic neuropathy, and that NGF supplementation rescues silent myocardial ischemia in DM. Cardiac innervation patterning is disrupted in Sema3a-deficient and Sema3a-overexpressing mice, leading to sudden death or lethal arrhythmias. The present review focuses on the regulatory mechanisms underlying cardiac innervation and the critical role of these processes in cardiac performance.
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Affiliation(s)
| | - Keiichi Fukuda
- Department of Regenerative Medicine and Advanced Cardiac Therapeutics, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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Okano Y, Tamura K, Kuji T, Masuda S, Tochikubo O, Umemura S. Effects of Angiotensin II Receptor Blockers on Relationships Between 24-Hour Blood Pressure, Autonomic Function, and Health-Related QOL. Clin Exp Hypertens 2009; 31:250-8. [DOI: 10.1080/10641960902822500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Takimoto C, Kumagai H, Osaka M, Sakata K, Onami T, Kamayachi T, Iigaya K, Hayashi K, Saruta T, Itoh H. Candesartan and Insulin Reduce Renal Sympathetic Nerve Activity in Hypertensive Type 1 Diabetic Rats. Hypertens Res 2008; 31:1941-51. [DOI: 10.1291/hypres.31.1941] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Ieda M, Kanazawa H, Ieda Y, Kimura K, Matsumura K, Tomita Y, Yagi T, Onizuka T, Shimoji K, Ogawa S, Makino S, Sano M, Fukuda K. Nerve Growth Factor Is Critical for Cardiac Sensory Innervation and Rescues Neuropathy in Diabetic Hearts. Circulation 2006; 114:2351-63. [PMID: 17101855 DOI: 10.1161/circulationaha.106.627588] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Molecular mechanisms regulating the cardiac sensory nervous system remain poorly understood. Cardiac sensory nerve impairment causes silent myocardial ischemia, a main cause of sudden death in diabetes mellitus (DM). The present study focused on the roles of nerve growth factor (NGF) in the regulation of the cardiac sensory nervous system and analyzed the mechanism of silent myocardial ischemia in DM. METHODS AND RESULTS We screened neurotrophic factors and found that cardiac sensory nerves developed in parallel with NGF synthesized in the heart. Cardiac nociceptive sensory nerves that were immunopositive for calcitonin gene-related peptide, dorsal root ganglia (DRG), and the dorsal horn were markedly retarded in NGF-deficient mice, whereas cardiac-specific overexpression of NGF rescued these deficits. DM was induced with streptozotocin in wild-type and transgenic mice overexpressing NGF in the heart. Downregulation of NGF, calcitonin gene-related peptide-immunopositive cardiac sensory denervation, and atrophic changes in DRG were observed in DM-induced wild-type mice, whereas these deteriorations were reversed in DM-induced NGF transgenic mice. Cardiac sensory function, measured by myocardial ischemia-induced c-Fos expression in DRG, was also downregulated by DM in the wild-type mice but not in NGF transgenic mice. Direct gene transfer of NGF in the diabetic rat hearts improved impaired cardiac sensory innervation and function, determined by electrophysiological activity of cardiac afferent nerves during myocardial ischemia. CONCLUSIONS These findings demonstrate that the development and regulation of the cardiac sensory nervous system are dependent on NGF synthesized in the heart and that DM-induced NGF reduction causes cardiac sensory neuropathy.
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Affiliation(s)
- Masaki Ieda
- Department of Regenerative Medicine and Advanced Cardiac Therapeutics, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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Matsuura T, Kumagai H, Onimaru H, Kawai A, Iigaya K, Onami T, Sakata K, Oshima N, Sugaya T, Saruta T. Electrophysiological properties of rostral ventrolateral medulla neurons in angiotensin II 1a receptor knockout mice. Hypertension 2005; 46:349-54. [PMID: 15998710 DOI: 10.1161/01.hyp.0000173421.97463.ac] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We compared the electrophysiological properties of neurons in the rostral ventrolateral medulla of neonatal angiotensin II type 1a receptor knockout mice and wild-type mice with responses to angiotensin II, its type-1 receptor blocker candesartan, and its type-2 receptor blocker PD123319. Using the whole-cell patch-clamp technique, we examined the characteristics of rostral ventrolateral medulla neurons in brain stem-spinal cord preparations in which the sympathetic neuronal network is preserved. Baseline membrane potential and firing rate were almost similar between angiotensin II type 1a receptor knockout mice and wild-type mice. Superfusion with angiotensin II depolarized rostral ventrolateral medulla bulbospinal neurons in wild-type mice, whereas it hyperpolarized those in angiotensin II type 1a receptor knockout mice. Because pretreatment with candesartan significantly prevented the angiotensin II-induced depolarization in wild-type mice, the angiotensin II type 1 receptor is crucial for this depolarization. Superfusion with PD123319 depolarized rostral ventrolateral medulla bulbospinal neurons in angiotensin II type 1a receptor knockout mice. PD123319 prevented the angiotensin II-induced hyperpolarization in angiotensin II type 1a receptor knockout mice, and, rather, it induced depolarization. These results suggest that the angiotensin II type 2 receptor in rostral ventrolateral medulla plays an antagonistic role against the angiotensin II type 1a receptor in controlling the neuronal activity of rostral ventrolateral medulla.
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Affiliation(s)
- Tomokazu Matsuura
- Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Tokyo 160-8582, Japan
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Osaka M, Kumagai H, Sakata K, Onami T, Chon KH, Watanabe MA, Saruta T. Low-order chaos in sympathetic nerve activity and scaling of heartbeat intervals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2003; 67:041915. [PMID: 12786404 DOI: 10.1103/physreve.67.041915] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2002] [Revised: 01/13/2003] [Indexed: 05/24/2023]
Abstract
The mechanism of 1/f scaling of heartbeat intervals remains unknown. We recorded heartbeat intervals, sympathetic nerve activity, and blood pressure in conscious rats with normal or high blood pressure. Using nonlinear analyses, we demonstrate that the dynamics of this system of three variables is low-order chaos, and that sympathetic nerve activity leads to heartbeat interval and blood pressure changes. It is suggested that impaired regulation of blood pressure by sympathetic nerve activity is likely to cause experimentally observable steeper scaling of heartbeat intervals in hypertensive (high blood pressure) rats.
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Affiliation(s)
- Motohisa Osaka
- Department of Life Information Sciences, Institute of Gerontology, Nippon Medical School, 1-396 Kosugi, Nakahara-ku, Kawasaki 211-8533, Japan.
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Matsuura T, Kumagai H, Kawai A, Onimaru H, Imai M, Oshima N, Sakata K, Saruta T. Rostral ventrolateral medulla neurons of neonatal Wistar-Kyoto and spontaneously hypertensive rats. Hypertension 2002; 40:560-5. [PMID: 12364363 DOI: 10.1161/01.hyp.0000032043.64223.87] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We compared the electrophysiological properties of neurons in the rostral ventrolateral medulla (RVLM) of neonatal Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), and responses to angiotensin II and its type 1 receptor antagonist candesartan. Using the whole-cell patch-clamp technique, we examined the characteristics of RVLM neurons in brainstem-spinal cord preparations with a preserved sympathetic neuronal network. The baseline membrane potential of irregularly firing neurons was less negative (-50.1+/-0.6 versus -52.0+/-0.6 mV) and the firing rate was faster (3.0+/-0.2 versus 2.0+/-0.2 Hz) in SHR (n=56) than in WKY (n=38). Superfusion with angiotensin II (6 micromol/L) significantly depolarized the RVLM bulbospinal neurons in SHR (5.4+/-1.1 mV, n=15) but not in WKY. In contrast, candesartan (0.12 micromol/L) induced a significant membrane hyperpolarization (-3.7+/-0.4 mV; n=14) and a decrease in the firing rate in RVLM bulbospinal neurons of SHR but not of WKY. These results suggest that endogenously generated angiotensin II binds to type 1 receptors on RVLM bulbospinal neurons, thus tonically contributing to a higher membrane potential and a faster firing rate in SHR. The electrophysiological properties of RVLM neurons and their responses to angiotensin II and candesartan differ between neonatal WKY and SHR. These differences in RVLM neurons suggest a mechanism that possibly leads to elevation in blood pressure.
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Affiliation(s)
- Tomokazu Matsuura
- Department of Internal Medicine, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
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