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Iovino M, Messana T, De Pergola G, Iovino E, Guastamacchia E, Licchelli B, Vanacore A, Giagulli VA, Triggiani V. Brain Angiotensinergic Regulation of the Immune System: Implications for Cardiovascular and Neuroendocrine Responses. Endocr Metab Immune Disord Drug Targets 2020; 20:15-24. [PMID: 31237219 DOI: 10.2174/1871530319666190617160934] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 05/08/2019] [Accepted: 05/08/2019] [Indexed: 01/09/2023]
Abstract
OBJECTIVE The Renin-Angiotensin-Aldosterone System (RAAS) plays a major role in the regulation of cardiovascular functions, water and electrolytic balance, and hormonal responses. We perform a review of the literature, aiming at providing the current concepts regarding the angiotensin interaction with the immune system in the brain and the related implications for cardiovascular and neuroendocrine responses. METHODS Appropriate keywords and MeSH terms were identified and searched in Pubmed. Finally, references of original articles and reviews were examined. RESULTS Angiotensin II (ANG II), beside stimulating aldosterone, vasopressin and CRH-ACTH release, sodium and water retention, thirst, and sympathetic nerve activity, exerts its effects on the immune system via the Angiotensin Type 1 Receptor (AT 1R) that is located in the brain, pituitary, adrenal gland, and kidney. Several actions are triggered by the binding of circulating ANG II to AT 1R into the circumventricular organs that lack the Blood-Brain-Barrier (BBB). Furthermore, the BBB becomes permeable during chronic hypertension thereby ANG II may also access brain nuclei controlling cardiovascular functions. Subfornical organ, organum vasculosum lamina terminalis, area postrema, paraventricular nucleus, septal nuclei, amygdala, nucleus of the solitary tract and retroventral lateral medulla oblongata are the brain structures that mediate the actions of ANG II since they are provided with a high concentration of AT 1R. ANG II induces also T-lymphocyte activation and vascular infiltration of leukocytes and, moreover, oxidative stress stimulating inflammatory responses via inhibition of endothelial progenitor cells and stimulation of inflammatory and microglial cells facilitating the development of hypertension. CONCLUSION Besides the well-known mechanisms by which RAAS activation can lead to the development of hypertension, the interactions between ANG II and the immune system at the brain level can play a significant role.
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Affiliation(s)
- Michele Iovino
- Interdisciplinary Department of Medicine-Section of Internal Medicine, Geriatrics, Endocrinology and Rare Diseases, University of Bari "Aldo Moro", School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Tullio Messana
- Infantile Neuropsychiatry, IRCCS - Institute of Neurological Sciences, Bologna, Italy
| | - Giovanni De Pergola
- Clinical Nutrition Unit, Medical Oncology, Department of Internal Medicine and Clinical Oncology, University of Bari, School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Emanuela Iovino
- Interdisciplinary Department of Medicine-Section of Internal Medicine, Geriatrics, Endocrinology and Rare Diseases, University of Bari "Aldo Moro", School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Edoardo Guastamacchia
- Interdisciplinary Department of Medicine-Section of Internal Medicine, Geriatrics, Endocrinology and Rare Diseases, University of Bari "Aldo Moro", School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Brunella Licchelli
- Interdisciplinary Department of Medicine-Section of Internal Medicine, Geriatrics, Endocrinology and Rare Diseases, University of Bari "Aldo Moro", School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Aldo Vanacore
- Interdisciplinary Department of Medicine-Section of Internal Medicine, Geriatrics, Endocrinology and Rare Diseases, University of Bari "Aldo Moro", School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Vito A Giagulli
- Interdisciplinary Department of Medicine-Section of Internal Medicine, Geriatrics, Endocrinology and Rare Diseases, University of Bari "Aldo Moro", School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
| | - Vincenzo Triggiani
- Interdisciplinary Department of Medicine-Section of Internal Medicine, Geriatrics, Endocrinology and Rare Diseases, University of Bari "Aldo Moro", School of Medicine, Policlinico, Piazza Giulio Cesare 11, 70124 Bari, Italy
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Abstract
The causes of essential hypertension remain an enigma. Interactions between genetic and external factors are generally recognized to act as aetiological mechanisms that trigger the pathogenesis of high blood pressure. However, the questions of which genes and factors are involved, and when and where such interactions occur, remain unresolved. Emerging evidence indicates that the hypertensive response to pressor stimuli, like many other physiological and behavioural adaptations, can become sensitized to particular stimuli. Studies in animal models show that, similarly to other response systems controlled by the brain, hypertensive response sensitization (HTRS) is mediated by neuroplasticity. The brain circuitry involved in HTRS controls the sympathetic nervous system. This Review outlines evidence supporting the phenomenon of HTRS and describes the range of physiological and psychosocial stressors that can produce a sensitized hypertensive state. Also discussed are the cellular and molecular changes in the brain neural network controlling sympathetic tone involved in long-term storage of information relating to stressors, which could serve to maintain a sensitized state. Finally, this Review concludes with a discussion of why a sensitized hypertensive response might previously have been beneficial and increased biological fitness under some environmental conditions and why today it has become a health-related liability.
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Affiliation(s)
- Alan Kim Johnson
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, USA.
- Department of Health and Human Physiology, University of Iowa, Iowa City, IA, USA.
- Department of Pharmacology, University of Iowa, Iowa City, IA, USA.
- The François M. Abboud Cardiovascular Center, Iowa City, IA, USA.
| | - Baojian Xue
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, USA
- The François M. Abboud Cardiovascular Center, Iowa City, IA, USA
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Wang G, Yeung CK, Wong WY, Zhang N, Wei YF, Zhang JL, Yan Y, Wong CY, Tang JJ, Chuai M, Lee KKH, Wang LJ, Yang X. Liver Fibrosis Can Be Induced by High Salt Intake through Excess Reactive Oxygen Species (ROS) Production. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:1610-1617. [PMID: 26843032 DOI: 10.1021/acs.jafc.5b05897] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
High salt intake has been known to cause hypertension and other side effects. However, it is still unclear whether it also affects fibrosis in the mature or developing liver. This study demonstrates that high salt exposure in mice (4% NaCl in drinking water) and chick embryo (calculated final osmolality of the egg was 300 mosm/L) could lead to derangement of the hepatic cords and liver fibrosis using H&E, PAS, Masson, and Sirius red staining. Meanwhile, Desmin immunofluorescent staining of mouse and chick embryo livers indicated that hepatic stellate cells were activated after the high salt exposure. pHIS3 and BrdU immunohistological staining of mouse and chick embryo livers indicated that cell proliferation decreased; as well, TUNEL analyses indicated that cell apoptosis increased in the presence of high salt exposure. Next, dihydroethidium staining on the cultured chick hepatocytes indicated the excess ROS was generated following high salt exposure. Furthermore, AAPH (a known inducer of ROS production) treatment also induced the liver fibrosis in chick embryo. Positive Nrf2 and Keap1 immunohistological staining on mouse liver suggested that Nrf2/Keap1 signaling was involved in high salt induced ROS production. Finally, the CCK8 assay was used to determine whether or not the growth inhibitory effect induced by high salt exposure can be rescued by antioxidant vitamin C. Meanwhile, the RT-PCR result indicated that the Nrf2/Keap1 downsteam genes including HO-1, NQO-1, and SOD2 were involved in this process. In sum, these experiments suggest that high salt intake would lead to high risk of liver damage and fibrosis in both adults and developing embryos. The pathological mechanism may be the result from an imbalance between oxidative stress and the antioxidant system.
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Affiliation(s)
- Guang Wang
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Cheung-kwan Yeung
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Wing-Yan Wong
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Nuan Zhang
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Yi-fan Wei
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Jing-li Zhang
- Institute of Vascular Biological Sciences, Guangdong Pharmaceutical University , Guangzhou 510006, China
| | - Yu Yan
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Ching-yee Wong
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Jun-jie Tang
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
| | - Manli Chuai
- Division of Cell and Developmental Biology, University of Dundee , Dundee DD1 5EH, United Kingdom
| | - Kenneth Ka Ho Lee
- Key Laboratory for Regenerative Medicine of the Ministry of Education, School of Biomedical Sciences, Chinese University of Hong Kong , Shatin, Hong Kong, China
| | - Li-jing Wang
- Institute of Vascular Biological Sciences, Guangdong Pharmaceutical University , Guangzhou 510006, China
| | - Xuesong Yang
- Division of Histology and Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University , Guangzhou 510632, China
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Johnson AK, Zhang Z, Clayton SC, Beltz TG, Hurley SW, Thunhorst RL, Xue B. The roles of sensitization and neuroplasticity in the long-term regulation of blood pressure and hypertension. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1309-25. [PMID: 26290101 PMCID: PMC4698407 DOI: 10.1152/ajpregu.00037.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 05/18/2015] [Indexed: 01/01/2023]
Abstract
After decades of investigation, the causes of essential hypertension remain obscure. The contribution of the nervous system has been excluded by some on the basis that baroreceptor mechanisms maintain blood pressure only over the short term. However, this point of view ignores one of the most powerful contributions of the brain in maintaining biological fitness-specifically, the ability to promote adaptation of behavioral and physiological responses to cope with new challenges and maintain this new capacity through processes involving neuroplasticity. We present a body of recent findings demonstrating that prior, short-term challenges can induce persistent changes in the central nervous system to result in an enhanced blood pressure response to hypertension-eliciting stimuli. This sensitized hypertensinogenic state is maintained in the absence of the inducing stimuli, and it is accompanied by sustained upregulation of components of the brain renin-angiotensin-aldosterone system and other molecular changes recognized to be associated with central nervous system neuroplasticity. Although the heritability of hypertension is high, it is becoming increasingly clear that factors beyond just genes contribute to the etiology of this disease. Life experiences and attendant changes in cellular and molecular components in the neural network controlling sympathetic tone can enhance the hypertensive response to recurrent, sustained, or new stressors. Although the epigenetic mechanisms that allow the brain to be reprogrammed in the face of challenges to cardiovascular homeostasis can be adaptive, this capacity can also be maladaptive under conditions present in different evolutionary eras or ontogenetic periods.
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Affiliation(s)
- Alan Kim Johnson
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; Department of Health and Human Physiology, The University of Iowa, Iowa City, Iowa; Department of Pharmacology, The University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, The University of Iowa, Iowa City, Iowa; and
| | - Zhongming Zhang
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; Nanyang Institute of Technology, Zhang Zhongjing College of Chinese Medicine, Nanyang, Henan Province, China
| | - Sarah C Clayton
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa
| | - Terry G Beltz
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa
| | - Seth W Hurley
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa
| | - Robert L Thunhorst
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, The University of Iowa, Iowa City, Iowa; and
| | - Baojian Xue
- Department of Psychological and Brain Sciences, The University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, The University of Iowa, Iowa City, Iowa; and
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Tousoulis D, Michalea S, Siasos G, Oikonomou E, Athanasiou D, Tourikis P, Kokkou E, Mazaris S, Konsola T, Papageorgiou N, Stefanadis C. Cystatin-C serum levels and vascular function in heart failure. Int J Cardiol 2014; 173:542-4. [PMID: 24704396 DOI: 10.1016/j.ijcard.2014.03.083] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 03/12/2014] [Indexed: 11/30/2022]
Affiliation(s)
- Dimitris Tousoulis
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece.
| | - Stavroula Michalea
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Gerasimos Siasos
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece; Department of Biological Chemistry, University of Athens Medical School, Athens, Greece
| | - Evangelos Oikonomou
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Dimitris Athanasiou
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Panagiotis Tourikis
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Eleni Kokkou
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Savvas Mazaris
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Theodosia Konsola
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Nikolaos Papageorgiou
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
| | - Christodoulos Stefanadis
- 1st Department of Cardiology, University of Athens Medical School, "Hippokration" Hospital, Athens, Greece
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Collister JP, Nahey DB, Hendel MD, Brooks VL. Roles of the subfornical organ and area postrema in arterial pressure increases induced by 48-h water deprivation in normal rats. Physiol Rep 2014; 2:e00191. [PMID: 24744870 PMCID: PMC3967674 DOI: 10.1002/phy2.191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 11/26/2013] [Accepted: 11/27/2013] [Indexed: 12/19/2022] Open
Abstract
In rats, water deprivation (WD) increases arterial blood pressure (BP) in part due to actions of elevated osmolality in the brain to increase vasopressin levels and sympathetic activity. However, the osmoreceptors that mediate this response have not been identified. To test the hypothesis that osmoregulatory circumventricular organs are involved, BP and heart rate (HR) were continuously recorded telemetrically during 48 h of WD in normal rats with lesions (x) or sham lesions (sham) of the subfornical organ (SFO) or area postrema (AP). Although WD increased BP in SFOx and SFOsham rats, no significant difference in the hypertensive response was observed between groups. HR decreased transiently but similarly in SFOx and SFOsham rats during the first 24 h of WD. When water was reintroduced, BP and HR decreased rapidly and similarly in both groups. BP (during lights off) and HR were both lower in APx rats before WD compared to APsham. WD increased BP less in APx rats, and the transient bradycardia was eliminated. Upon reintroduction of drinking water, smaller falls in both BP and HR were observed in APx rats compared to APsham rats. WD increased plasma osmolality and vasopressin levels similarly in APx and APsham rats, and acute blockade of systemic V1 vasopressin receptors elicited similar depressor responses, suggesting that the attenuated BP response is not due to smaller increases in vasopressin or osmolality. In conclusion, the AP, but not the SFO, is required for the maximal hypertensive effect induced by WD in rats.
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Affiliation(s)
- John P Collister
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, 55108, Minnesota
| | - David B Nahey
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, 55108, Minnesota
| | - Michael D Hendel
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, 55108, Minnesota
| | - Virginia L Brooks
- Department of Physiology & Pharmacology, Oregon Health and Science University Portland, Oregon, 97239
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Role of the Median Preoptic Nucleus in Arterial Pressure Regulation and Sodium and Water Homeostasis during High Dietary Salt Intake. NEUROPHYSIOLOGY+ 2012; 44:363-375. [PMID: 32724266 DOI: 10.1007/s11062-012-9307-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Changes in the osmolality and level of angiotensin II (ANG II) are important peripheral signals modulating appropriate central sympathetic output and maintaining a normal arterial pressure during high salt intake. The median preoptic nucleus (MnPO) receives reciprocal inputs from the subfornical organ (SFO) and organum vasculosum of the lamina terminalis (OVLT), the circumventricular organs that have been shown to be necessary in multiple central effects of changes in the osmolality and circulating ANG II directed toward the maintenance of sodium and water homeostasis. We, therefore, hypothesized that the MnPO is a crucial part of the central neuronal mechanisms mediating the blood pressure control by altered osmolality and/or ANG II signaling during chronic high dietary salt intake. Male Sprague-Dawley rats were randomly assigned to either sham (operation), or electrolytic lesion of the MnPO. After a 7-day recovery, rats were instrumented with radiotelemetric transducers and aortic flow probes for the measurement of the mean arterial pressure + heart rate (HR) and cardiac output (CO), respectively. Femoral venous catheters were also implanted to collect blood for the measurements of plasma osmolality and sodium concentration, as well as plasma renin activity. Rats were given another 10 days to recover and then were subjected to a 28-day-long study protocol that included a 7-day control period (1.0% NaCl diet), followed by 14 days of high salt (4.0% NaCl), and a 7-day recovery period (1.0% NaCl). The data showed, that despite a slight increase in the MAP observed in both MnPO- (n = 12) and sham-lesioned (n = 8) rats during the high-salt period, there were no significant differences between the MAP, HR, and CO in the two groups throughout the study protocol. These findings do not support the hypothesis that the MnPO is necessary to maintain normal blood pressure during high dietary salt intake. However, MnPO-lesioned rats showed less sodium balance than sham-lesioned rats during the first 4 days of high salt intake. Although, these results may be explained partly by the plasma hyperosmolarity and hypernatremia observed in MnPO-lesioned rats; they also shed light on the role of the MnPO in central neuronal control of renal sodium handling during chronic high dietary salt intake.
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Osborn JW, Hendel MD, Collister JP, Ariza-Guzman PA, Fink GD. The role of the subfornical organ in angiotensin II-salt hypertension in the rat. Exp Physiol 2012; 97:80-8. [PMID: 21967900 PMCID: PMC3253211 DOI: 10.1113/expphysiol.2011.060491] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Hypertension caused by chronic infusion of angiotensin II (Ang II) in experimental animals is dependent, in part, on increased activity of the sympathetic nervous system. This chronic sympathoexcitatory response is amplified by a high-salt diet, suggesting an interaction of circulating Ang II and dietary salt on sympathetic regulatory pathways in the brain. The present study tested the hypothesis that the subfornical organ (SFO), a forebrain circumventricular organ known to be activated by circulating Ang II, is crucial to the pathogenesis of hypertension induced by chronic Ang II administration in rats on a high-salt diet (Ang II-salt model). Rats were randomly selected to undergo either subfornical organ lesion (SFOx) or sham surgery (Sham) and then placed on a high-salt (2% NaCl) diet. One week later, rats were instrumented for radiotelemetric measurement of mean arterial pressure (MAP) and heart rate (HR) and placed in metabolic cages to measure sodium and water balance. Baseline MAP was slightly (but not statistically) lower in SFOx compared with Sham rats during the 5 day control period. During the subsequent 10 days of Ang II administration, MAP was statistically lower in SFOx rats. However, when MAP responses to Ang II were analysed by comparing the change from the 5 day baseline period, only on the fifth day of Ang II was MAP significantly different between groups. There were no differences between groups for water or sodium balance throughout the protocol. We conclude that, although the SFO is required for the complete expression of Ang II-salt hypertension in the rat, other brain sites are also involved.
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Affiliation(s)
- John W Osborn
- Department of Integrative Biology and Physiology, University of Minnesota, Room 6-125 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA.
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Chen QH, Andrade MA, Calderon AS, Toney GM. Hypertension induced by angiotensin II and a high salt diet involves reduced SK current and increased excitability of RVLM projecting PVN neurons. J Neurophysiol 2010; 104:2329-37. [PMID: 20719931 DOI: 10.1152/jn.01013.2009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although evidence indicates that activation of presympathetic paraventricular nucleus (PVN) neurons contributes to the pathogenesis of salt-sensitive hypertension, the underlying cellular mechanisms are not fully understood. Recent evidence indicates that small conductance Ca(2+)-activated K(+) (SK) channels play a significant role in regulating the excitability of a key group of sympathetic regulatory PVN neurons, those with axonal projections to the rostral ventrolateral medulla (RVLM; i.e., PVN-RVLM neurons). In the present study, rats consuming a high salt (2% NaCl) diet were made hypertensive by systemic infusion of angiotensin II (AngII), and whole cell patch-clamp recordings were made in brain slice from retrogradely labeled PVN-RVLM neurons. To determine if the amplitude of SK current was altered in neurons from hypertensive rats, voltage-clamp recordings were performed to isolate SK current. Results indicate that SK current amplitude (P < 0.05) and density (P < 0.01) were significantly smaller in the hypertensive group. To investigate the impact of this on intrinsic excitability, current-clamp recordings were performed in separate groups of PVN-RVLM neurons. Results indicate that the frequency of spikes evoked by current injection was significantly higher in the hypertensive group (P < 0.05-0.01). Whereas bath application of the SK channel blocker apamin significantly increased discharge of neurons from normotensive rats (P < 0.05-0.01), no effect was observed in the hypertensive group. In response to ramp current injections, subthreshold depolarizing input resistance was greater in the hypertensive group compared with the normotensive group (P < 0.05). Blockade of SK channels increased depolarizing input resistance in normotensive controls (P < 0.05) but had no effect in the hypertensive group. On termination of current pulses, a medium afterhyperpolarization potential (mAHP) was observed in most neurons of the normotensive group. In the hypertensive group, the mAHP was either small or absent. In the latter case, an afterdepolarization potential (ADP) was observed that was unaffected by apamin. Apamin treatment in the normotensive group blocked the mAHP and revealed an ADP resembling that seen in the hypertensive group. We conclude that diminished SK current likely underlies the absence of mAHPs in PVN-RVLM neurons from hypertensive rats. Both the ADP and greater depolarizing input resistance likely contribute to increased excitability of PVN-RVLM neurons from rats with AngII-Salt hypertension.
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Affiliation(s)
- Qing-Hui Chen
- Exercise Science, Health and Physical Education Department, Michigan Technological University, Houghton, Michigan; USA.
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Malpas SC. Sympathetic nervous system overactivity and its role in the development of cardiovascular disease. Physiol Rev 2010; 90:513-57. [PMID: 20393193 DOI: 10.1152/physrev.00007.2009] [Citation(s) in RCA: 431] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
This review examines how the sympathetic nervous system plays a major role in the regulation of cardiovascular function over multiple time scales. This is achieved through differential regulation of sympathetic outflow to a variety of organs. This differential control is a product of the topographical organization of the central nervous system and a myriad of afferent inputs. Together this organization produces sympathetic responses tailored to match stimuli. The long-term control of sympathetic nerve activity (SNA) is an area of considerable interest and involves a variety of mediators acting in a quite distinct fashion. These mediators include arterial baroreflexes, angiotensin II, blood volume and osmolarity, and a host of humoral factors. A key feature of many cardiovascular diseases is increased SNA. However, rather than there being a generalized increase in SNA, it is organ specific, in particular to the heart and kidneys. These increases in regional SNA are associated with increased mortality. Understanding the regulation of organ-specific SNA is likely to offer new targets for drug therapy. There is a need for the research community to develop better animal models and technologies that reflect the disease progression seen in humans. A particular focus is required on models in which SNA is chronically elevated.
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Affiliation(s)
- Simon C Malpas
- Department of Physiology and the Auckland Bioengineering Institute, University of Auckland and Telemetry Research Ltd., Auckland, New Zealand.
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Huang J, Xie T, Wu Y, Li X, Lusina S, Ji ES, Xiang S, Liu Y, Gautam S, Weiss JW. Cyclic intermittent hypoxia enhances renal sympathetic response to ICV ET-1 in conscious rats. Respir Physiol Neurobiol 2010; 171:83-9. [PMID: 20227529 DOI: 10.1016/j.resp.2010.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 03/01/2010] [Accepted: 03/05/2010] [Indexed: 11/26/2022]
Abstract
To test the hypothesis that central changes in sympathoregulation might contribute to sympathoexcitation after cyclic intermittent hypoxia (CIH) we exposed male Sprague-Dawley rats to CIH or to room air sham (Sham) for 8h/d for 3 weeks. After completion of the exposure we assessed heart rate, mean arterial pressure and renal sympathetic nerve activity in conscious animals before and after intracerebroventricular (i.c.v.) administration of endothelin-1 (ET-1, 3 pmol). CIH-exposed animals had a significantly greater sympathetic response to ET-1 than did Sham-exposed animals (CIH 137.8+/-15.6% of baseline; Sham 112.2+/-10.0% of baseline; CIH vs. Sham, P=0.0373). This enhanced sympathetic response to i.c.v. ET-1 was associated with greater expression of endothelin receptor A (ETA) protein in the subfornical organs of CIH-exposed relative to Sham-exposed rats. We conclude that 3-week CIH exposure enhances central ET-1 receptor expression and the sympathetic response to i.c.v. ET-1 suggesting central endothelin may contribute to the sympathetic and hemodynamic response to cyclic intermittent hypoxia.
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Affiliation(s)
- Jianhua Huang
- Pulmonary and Sleep Research Laboratory, Division of Pulmonary, Critical Care & Sleep Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
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Role of GABAB Receptors in Autonomic Control of Systemic Blood Pressure. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:257-86. [DOI: 10.1016/s1054-3589(10)58011-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Zhang Q, Yao F, O'Rourke ST, Qian SY, Sun C. Angiotensin II enhances GABA(B) receptor-mediated responses and expression in nucleus tractus solitarii of rats. Am J Physiol Heart Circ Physiol 2009; 297:H1837-44. [PMID: 19749158 DOI: 10.1152/ajpheart.00354.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Angiotensin II (ANG II) increases GABA(B) receptor expression in neuronal cultures from the nucleus tractus solitarii (NTS). In the present study, the chronic effects of ANG II on GABA(B) receptor expression and activity were examined in the NTS of Sprague-Dawley rats. Intracerebroventricular infusion of ANG II caused a significant elevation in blood pressure (BP) and an increase in GABA(B) receptor expression in the NTS. Conversely, chronic N(G)-nitro-l-arginine methyl ester (l-NAME) treatment also increased BP, but had no effect on GABA(B) receptor expression in the NTS. Next, we examined the BP response to the GABA(B) receptor agonist baclofen microinjected into the NTS of ANG II- or artificial cerebrospinal fluid (aCSF)-infused rats. NTS microinjection of baclofen increased BP in both groups of rats. However, the pressor response to baclofen was enhanced in ANG II-infused rats compared with aCSF-infused rats. In addition, bilateral microinjection of the GABA(B) receptor antagonist CGP-35348 into the NTS evoked a decrease in BP in both group of rats, and the depressor responses to CGP-35348 were enhanced in the ANG II-infused rats. In contrast, the pressor responses to the GABA(A) receptor agonist muscimol and the depressor responses to the GABA(A) receptor antagonist bicuculline were comparable between aCSF- and ANG II-infused rats. These results indicate that chronic ANG II infusion stimulates GABA(B) receptor expression and augments GABA(B) receptor-mediated responses in the NTS. This effect could contribute to the central nervous system actions of ANG II that result in dampening of baroreflexes and elevation in arterial BP.
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Affiliation(s)
- Qi Zhang
- Department of Pharmaceutical Sciences, College of Pharmacy, North Dakota State University, Fargo, ND 58105, USA
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14
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Stachenfeld NS. Acute effects of sodium ingestion on thirst and cardiovascular function. Curr Sports Med Rep 2009; 7:S7-13. [PMID: 18843231 DOI: 10.1249/jsr.0b013e31817f23fc] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Sweating during exercise, especially during exercise in the heat, leads to sodium and water losses, and the quantity of these losses depends upon the intensity and duration of the activity, genetic predisposition and conditioning of the individual, and environmental factors. In athletes, adequate sodium intake is necessary to maintain fluid balance during training and competition. To ensure the precise regulation of volume and osmolality of body fluids, a number of integrated neural and hormonal systems have evolved to control thirst and sodium appetite. These systems respond to stimuli that arise from a deficit of fluid arising in both the intracellular and extracellular fluid compartments or to systemic hypertonicity. Thirst is highly sensitive to increases in plasma sodium concentration and osmolality, requiring only a 2%-3% increase to induce feelings of thirst. A larger change in plasma volume (10%) is required to induce thirst if there is no concomitant change in plasma sodium concentration. If plain water is used to replenish body water, plasma volume is preferentially restored over the interstitial and intracellular fluid space, suppressing plasma sodium concentration and removing the dipsogenic drive long before total body fluid has been restored. During or after dehydrating exercise, sodium ingestion helps to maintain and restore plasma volume and osmolality by continuing thirst sensation (thus drinking) and also by increasing body fluid retention. A high sodium meal or intravascular hypertonic saline infusion may cause transient osmotically mediated blood pressure increases, but in healthy people, acute sodium ingestion does not cause sustained hypertension. The purpose of this review is to provide evidence that acute increases in sodium are an intrinsic part of the thirst response during and after exercise, and that blood pressure increases associated with hypertonicity appear to be short lived.
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Affiliation(s)
- Nina S Stachenfeld
- The John B. Pierce Laboratory and Yale University School of Medicine, New Haven, Connecticut 06519, USA.
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15
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Madero M, Wassel CL, Peralta CA, Najjar SS, Sutton-Tyrrell K, Fried L, Canada R, Newman A, Shlipak MG, Sarnak MJ. Cystatin C associates with arterial stiffness in older adults. J Am Soc Nephrol 2009; 20:1086-93. [PMID: 19357259 DOI: 10.1681/asn.2008030318] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Large arteries commonly become stiff in kidney failure, but few studies have investigated arterial stiffness in earlier stages of kidney disease. We evaluated the association between kidney function and aortic pulse wave velocity (aPWV) and its potential modification by race, diabetes, or coronary heart disease in older adults. We measured aPWV in 2468 participants in the Health Aging and Body Composition (Health ABC) study; mean age was 73.7 yr, 40% were black, and 24% had diabetes. After categorizing kidney function into three groups on the basis of cystatin C level, multivariable analysis revealed that the medium and high cystatin C groups associated with a 5.3% (95% confidence interval 0.8 to 10.0%) and 8.0% (95% confidence interval 2.2 to 14.1%) higher aPWV than the low cystatin C group; however, chronic kidney disease, as defined by estimated GFR <60 ml/min per 1.73 m(2), did not significantly associate with aPWV. We did not identify interactions between cystatin C and race, diabetes, or coronary heart disease. In conclusion, stiffness of large arteries, a major risk factor for cardiovascular disease, may partially mediate the association between cystatin C and cardiovascular risk in older adults.
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Affiliation(s)
- Magdalena Madero
- Department of Nephrology, Instituto Nacional de Cardiología Ignacio Chávez México City, Mexico
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16
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Pogson ZEK, McKeever TM, Lewis SA, Pacey SJ, Antoniak MD, Britton JR, Fogarty AW. Does a low sodium diet modify heart rate variability? A randomised placebo-controlled double-blind trial. Int J Cardiol 2008; 135:390-3. [PMID: 19062112 DOI: 10.1016/j.ijcard.2008.11.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 11/01/2008] [Indexed: 11/29/2022]
Abstract
BACKGROUND Increased heart rate variability (HRV) is associated with a low risk of mortality, as is consuming a low sodium diet. As the survival benefits of a low sodium diet may be mediated partly by an increase in HRV, we have tested the hypothesis that adopting a low sodium diet increases HRV. METHODS We used a randomised double-blind placebo-controlled trial design. Participants were aged 18-65 years old, had a physician diagnosis of asthma. All adopted a low sodium diet and they were randomised to receive either 80 mmol/day of oral sodium supplements (normal sodium intake - NSI) or matched placebo (low sodium intake-LSI) for 6 weeks. The primary outcome was change in SDNN (standard deviation of the N-N intervals); secondary outcomes were changes in other time domain and frequency domain measures of HRV. RESULTS In those allocated to the LSI, mean daily urinary sodium excretion decreased by 22 mmol; and in those allocated to the NSI mean daily urinary sodium excretion increased by 31 mmol. There were no differences between the two groups for either the primary or secondary outcome measures. The mean difference in change in SDNN between those who received the LSI compared to the NSI was -2.7 ms (95% Confidence Intervals CI; -18.0 to +12.6). CONCLUSIONS Adopting a low sodium diet does not have an impact on SDNN over a 6 weeks period. Future studies should aim to achieve a larger change in dietary sodium intake for a longer duration than 6 weeks.
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17
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Yao F, Sumners C, O'Rourke ST, Sun C. Angiotensin II increases GABAB receptor expression in nucleus tractus solitarii of rats. Am J Physiol Heart Circ Physiol 2008; 294:H2712-20. [PMID: 18424635 PMCID: PMC4422374 DOI: 10.1152/ajpheart.00729.2007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Accepted: 04/15/2008] [Indexed: 11/22/2022]
Abstract
Increasing evidence indicates that both the angiotensin II (ANG II) and gamma-aminobutyric acid (GABA) systems play a very important role in the regulation of blood pressure (BP). However, there is little information concerning the interactions between these two systems in the nucleus tractus solitarii (NTS). In the present study, we examined the effects of ANG II on GABAA and GABAB receptor (GAR and GBR) expression in the NTS of Sprague-Dawley rats. The direct effect of ANG II on GBR expression was determined in neurons cultured from NTS. Treatment of neuronal cultures with ANG II (100 nM, 5 h) induced a twofold increase in GBR1 expression, as detected with real-time RT-PCR and Western blots, but had no effect on GBR2 or GAR expression. In electrophysiological experiments, perfusion of neuronal cultures with the GBR agonist baclofen decreased neuronal firing rate by 39% and 63% in neurons treated with either PBS (control) or ANG II, respectively, indicating that chronic ANG II treatment significantly enhanced the neuronal response to GBR activation. In contrast, ANG II had no significant effect on the inhibitory action of the GAR agonist muscimol. In whole animal studies, intracerebroventricular infusion of ANG II induced a sustained increase in mean BP and an elevation of GBR1 mRNA and protein levels in the NTS. These results indicate that ANG II stimulates GBR expression in NTS neurons, and this could contribute to the central nervous system actions of ANG II that result in dampening of baroreflexes and elevated BP in the central actions of ANG II.
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MESH Headings
- Action Potentials
- Angiotensin II/administration & dosage
- Angiotensin II/metabolism
- Animals
- Animals, Newborn
- Baclofen/pharmacology
- Baroreflex/drug effects
- Blood Pressure/drug effects
- Blotting, Western
- Cells, Cultured
- Disease Models, Animal
- GABA Agonists/pharmacology
- GABA-B Receptor Agonists
- Hypertension/chemically induced
- Hypertension/metabolism
- Hypertension/physiopathology
- Infusions, Parenteral
- Male
- Muscimol/pharmacology
- Neurons/drug effects
- Neurons/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptor, Angiotensin, Type 1/metabolism
- Receptor, Angiotensin, Type 2/metabolism
- Receptors, GABA-A/metabolism
- Receptors, GABA-B/genetics
- Receptors, GABA-B/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Solitary Nucleus/cytology
- Solitary Nucleus/drug effects
- Solitary Nucleus/metabolism
- Time Factors
- Up-Regulation
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Affiliation(s)
- Fanrong Yao
- Department of Pharmaceutical Sciences, College of Pharmacy, North Dakota State University, Fargo, North Dakota, USA
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18
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McBryde FD, Guild SJ, Barrett CJ, Osborn JW, Malpas SC. Angiotensin II-based hypertension and the sympathetic nervous system: the role of dose and increased dietary salt in rabbits. Exp Physiol 2007; 92:831-40. [PMID: 17468201 DOI: 10.1113/expphysiol.2007.037473] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
There is accumulating evidence that angiotensin II may exert its hypertensive effect through increasing sympathetic drive. However, this action may be dependent on the dose of angiotensin II as well as salt intake. We determined the effect of different doses of angiotensin II and different levels of salt intake on neurogenic pressor activity. We also examined the effect of renal denervation. New Zealand White rabbits were instrumented to continuously measure arterial pressure. The depressor response to the ganglionic blocker pentolinium tartrate (5 mg kg(-1)) was used to assess pressor sympathetic drive on days 0, 7 and 21 of a 20 or 50 ng kg(-1) min(-1) continuous i.v. angiotensin II infusion. A 50 ng kg(-1) min(-1) infusion caused an immediate increase in pressure (23 +/- 5 mmHg), whereas a 20 ng kg(-1) min(-1) infusion caused a slow increase in pressure, peaking by day 12 (17 +/- 4 mmHg). The ganglionic blockade profiles indicated sympathoinhibition in the 50 ng kg(-1) min(-1) group by day 7 and sympathoinhibition in the 20 ng kg(-1) min(-1) group at day 21, corresponding to the development of hypertension. Animals receiving increased dietary salt (0.9% NaCl in drinking water), however, showed a similar slow increase in pressure with 20 ng kg(-1) min(-1) angiotensin II (16 +/- 5 mmHg) but no sympathoinhibition at day 21. Bilateral renal denervation delayed the onset but not the extent of hypertension in this group. We conclude that different doses of angiotensin II produce distinct profiles of hypertension and associated changes in pressor sympathetic drive and that increased dietary salt intake disrupts the normal sympathoinhibitory response to angiotensin II-based hypertension.
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Affiliation(s)
- Fiona D McBryde
- Circulatory Control Laboratory, Department of Physiology and Bioengineering Institute, University of Auckland, Auckland, New Zealand
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19
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Kagota S, Kubota Y, Nejime N, Nakamura K, Kunitomo M, Shinozuka K. Impaired effect of salt loading on nitric oxide-mediated relaxation in aortas from stroke-prone spontaneously hypertensive rats. Clin Exp Pharmacol Physiol 2007; 34:48-54. [PMID: 17201735 DOI: 10.1111/j.1440-1681.2007.04532.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
1. The present study was designed to characterize the effects of salt on vasorelaxation via the nitric oxide (NO)/cGMP pathway in stroke-prone spontaneously hypertensive rats (SHRSP), which are highly salt sensitive. 2. Male 8-week-old SHRSP were given 1% NaCl solution as drinking water for 4 weeks, whereas control animals were given water only. 3. In aortic rings from salt-loaded SHRSP, relaxations in response to acetylcholine and sodium nitroprusside were significantly impaired compared with those in the control. In the presence of zaprinast, a cGMP-specific cyclic nucleotide phosphodiesterase (PDE)-5 inhibitor, the cGMP levels induced by these drugs were significantly reduced by salt loading, but remained unchanged in the absence of zaprinast. The protein levels of endothelial NO synthase, soluble guanylate cyclase (sGC) and cGMP-dependent protein kinase (PKG) remained unchanged with salt loading, but those of PDE-5 decreased significantly and those of phosphorylated PKG tended to decrease, although the change was not statistically significant. Salt loading significantly impaired the relaxation in response to 8-bromo-cGMP. 4. These results indicate that, in aortas from SHRSP, salt loading causes impairment of relaxation in response to NO, which may be due to a decrease in cGMP production by sGC and impairment of the relaxation pathway downstream of cGMP, which, in turn, probably causes a decrease in PKG activity. Reduced PDE-5 protein expression may act, in part, as a compensatory response to impairment of cGMP-mediated relaxation.
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Affiliation(s)
- Satomi Kagota
- Department of Pharmacology, School of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya, Japan.
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20
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Brooks VL, Freeman KL, Qi Y. Time course of synergistic interaction between DOCA and salt on blood pressure: roles of vasopressin and hepatic osmoreceptors. Am J Physiol Regul Integr Comp Physiol 2006; 291:R1825-34. [PMID: 16857894 DOI: 10.1152/ajpregu.00068.2006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In DOCA-salt rats, the time course of the synergistic interaction between osmolality and DOCA to produce hypertension is unknown. Therefore, in rats 2 wk after implantation of subcutaneous silicone pellets containing DOCA (65 mg) or no drug (sham), we determined blood pressure (BP) and heart rate (HR) responses, using telemetric pressure transducers, during 2 wk of excess salt ingestion (1% NaCl in drinking water). BP was unaltered in sham rats after increased salt, but in DOCA rats BP increased within 4 h. The initial hypertension of 30–35 mmHg stabilized within 2 days, followed ∼5 days later by a further increment of ∼30 mmHg. HR first decreased during the dark phase; the second phase was linked to an abrupt increase in HR and BP variability and decreased HR variability. Pressor responses to acute intravenous hypertonic saline infusion were doubled in DOCA-treated rats via vasopressin and nonvasopressin mechanisms. Only in DOCA-treated rats, portal vein hypertonic saline infusion increased BP, which was prevented by V1 vasopressin blockade. After 2 wk of DOCA-salt, oral ingestion of water rapidly decreased BP. Intraportal infusion of water did not lower BP in DOCA-salt rats, suggesting that hepatic osmoreceptors were not involved. In summary, the hypertension of DOCA-treated rats consuming excess salt exhibits multiple phases and can be rapidly reversed. Hypertonicity-induced vasopressin and nonvasopressin pressor mechanisms that are augmented by DOCA, and hepatic osmoreceptors may contribute to the initial developmental phase. With time, combined DOCA-salt induces marked changes in the regulation of the autonomic nervous system, which may favor hypertension development.
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Affiliation(s)
- Virginia L Brooks
- Department of Physiology and Pharmacology L-334, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA.
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21
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Ji LL, Gottlieb HB, Penny ML, Fleming T, Toney GM, Cunningham JT. Differential effects of water deprivation and rehydration on Fos and FosB/DeltaFosB staining in the rat brainstem. Exp Neurol 2006; 203:445-56. [PMID: 17027755 DOI: 10.1016/j.expneurol.2006.08.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Revised: 08/24/2006] [Accepted: 08/28/2006] [Indexed: 11/27/2022]
Abstract
This study examined the effects of dehydration and rehydration with water on Fos and FosB staining in the brainstem of rats. Male rats were water deprived for 48 h (Dehyd, n=7) or 46 h followed by 2 h access to water (Rehyd, n=7). Controls had ad libitum access to water (Con, n=9). Brainstems were stained for Fos and FosB/DeltaFosB using commercially available antibodies. In the nucleus of the solitary tract (NTS), the number of Fos stained neurons was significantly increased by dehydration and increased further following rehydration (Con 5+/-1; Dehyd 22+/-1; Rehyd 48+/-5). The average number of Fos-positive cells in the parabrachial nucleus (PBN) was significantly increased only by rehydration (Con 12+/-2; Dehyd 6+/-2; Rehyd 51+/-4). The area postrema (AP) showed significant increases in Fos staining after dehydration and rehydration (Fos: Con 4+/-1; Dehyd 28+/-3; Rehyd 24+/-3). In the rostral ventrolateral medulla (RVL), Fos staining significantly increased after dehydration and this effect was reduced by rehydration (Con 3+/-1; Dehyd 21+/-2; Rehyd 12+/-1). In contrast, Fos staining in the caudal ventrolateral medulla (CVL) was not significantly influenced following either dehydration or rehydration with water (Con 4+/-1; Dehyd 4+/-1; Rehyd 5+/-1). FosB/DeltaFosB staining in the NTS, AP, and RVL was comparably increased by dehydration and rehydration. In the PBN and CVL, FosB/DeltaFosB staining was not affected by the treatments. Dehydration and rehydration have regionally specific effects on Fos and FosB/DeltaFosB staining in the brainstem.
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Affiliation(s)
- Lisa L Ji
- Department of Pharmacology, and the Center for Biomedical Neuroscience, UTHSCSA, USA
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22
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Brooks VL, Haywood JR, Johnson AK. Translation of salt retention to central activation of the sympathetic nervous system in hypertension. Clin Exp Pharmacol Physiol 2006; 32:426-32. [PMID: 15854153 DOI: 10.1111/j.1440-1681.2005.04206.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
1. Increased dietary salt increases blood pressure in many hypertensive individuals, producing salt-sensitive hypertension (SSH). The cause is unknown, but a major component appears to be activation of the sympathetic nervous system. The purpose of this short review is to present one hypothesis to explain how increased dietary salt increases sympathetic activity in SSH. 2. It is proposed that increased salt intake causes salt retention and raises plasma sodium chloride (NaCl) concentrations, which activate sodium/osmoreceptors to trigger sympathoexcitation. Moreover, we suggest that small and often undetectable increases in osmolality can drive significant sympathoexcitation, because the gain of the relationship between osmolality and increased sympathetic activity is enhanced. Multiple factors may contribute to this facilitation, including inappropriately elevated levels of angiotensin II or aldosterone, changes in gene expression or synaptic plasticity and increased sodium concentrations in cerebrospinal fluid. 3. Future studies are required to delineate the brain sites and mechanisms of action and interaction of osmolality and these amplification factors to elicit sustained sympathoexcitation in SSH.
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Affiliation(s)
- Virginia L Brooks
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon 97239, USA.
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23
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Hendel MD, Collister JP. Sodium balance, arterial pressure, and the role of the subfornical organ during chronic changes in dietary salt. Am J Physiol Heart Circ Physiol 2005; 289:H426-31. [PMID: 15734879 DOI: 10.1152/ajpheart.01051.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The subfornical organ (SFO), one of the brain circumventricular organs, is known to mediate some of the central effects of angiotensin II related to sodium and water homeostasis. Because angiotensin II levels are altered with changes in chronic dietary salt intake, we reasoned that the actions of angiotensin II at the SFO might be involved in the regulation of arterial pressure during long-term alterations in dietary salt. The present study was designed to test the hypothesis that long-term control of arterial pressure during chronic changes in dietary salt intake requires an intact SFO. Male Sprague-Dawley rats were randomly selected for electrolytic lesion (SFOx, n = 8) or sham ( n = 9) operation of the SFO. After a 1-wk recovery period, rats were instrumented with radio-telemetric blood pressure transducers for continuous 24-h measurement of mean arterial pressure (MAP) and heart rate (HR) and then were placed individually in metabolic cages. After another 1 wk of recovery, the rats were subjected to a 49-day protocol as follows: 1) a 7-day control period (1.0% NaCl diet), 2) 14 days of high-salt (4.0% NaCl) diet, 3) 7 days of normal-salt (1.0% NaCl) diet, 4) 14 days of low-salt (0.1% NaCl) diet, and 5) 7 days of recovery (1.0% NaCl diet). There were no significant differences in MAP or HR between SFOx and sham-operated rats throughout the protocol. These results do not support the hypothesis that the SFO is necessary for regulation of arterial pressure during chronic changes in dietary salt. However, SFOx rats demonstrated significantly less cumulative sodium balance than sham-operated rats on days 2–6 of the high-salt diet period. These data suggest that the SFO is important in the regulation of sodium homeostasis during chronic changes in salt intake.
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Affiliation(s)
- Michael D Hendel
- Dept. of Veterinary and Biomedical Sciences, Univ. of Minnesota, 1988 Fitch Ave., Rm. 295G, St. Paul, MN 55108, USA.
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24
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Yang Z, Sibley DR, Jose PA. D5 dopamine receptor knockout mice and hypertension. J Recept Signal Transduct Res 2005; 24:149-64. [PMID: 15521360 DOI: 10.1081/rrs-200029971] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Abnormalities in dopamine production and receptor function have been described in human essential hypertension and rodent models of genetic hypertension. All of the five dopamine receptor genes (D1, D2, D3, D4, and D5) expressed in mammals and some of their regulators are in loci linked to hypertension in humans and in rodents. Under normal conditions, D1-like receptors (D1 and D5) inhibit sodium transport in the kidney and the intestine. However, in the Dahl salt-sensitive and spontaneously hypertensive rats, and humans with essential hypertension, the D1-like receptor-mediated inhibition of sodium transport is impaired because of an uncoupling of the D1-like receptor from its G protein/effector complex. The uncoupling is genetic, and receptor-, organ-, and nephron segment-specific. In human essential hypertension, the uncoupling of the D1 receptor from its G protein/effector complex is caused by an agonist-independent serine phosphorylation/desensitization by constitutively active variants of the G protein-coupled receptor kinase type 4. The D5 receptor is also important in blood pressure regulation. Disruption of the D5 or the D1 receptor gene in mice increases blood pressure. However, unlike the D1 receptor, the hypertension in D5 receptor null mice is caused by increased activity of the sympathetic nervous system, apparently due to activation of oxytocin, V1 vasopressin, and non-N-methyl D-aspartate receptors in the central nervous system. The cause of the activation of these receptors remains to be determined.
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Affiliation(s)
- Zhiwei Yang
- Georgetown University Medical Center, Washington, District of Columbia, USA.
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25
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Ross MG, Desai M. Gestational programming: population survival effects of drought and famine during pregnancy. Am J Physiol Regul Integr Comp Physiol 2005; 288:R25-33. [PMID: 15590994 DOI: 10.1152/ajpregu.00418.2004] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The process whereby a stimulus or stress at a critical or sensitive period of development has long-term effects is termed "programming." Studies in humans and animals convincingly demonstrate that environmental perturbations in utero may permanently change organ structure and metabolism and/or alter homeostatic regulatory mechanisms among the offspring. These programmed changes may be the origins of adult diseases, including cardiovascular disease, obesity, and diabetes. Throughout evolution and development, humans and animals have been exposed to two common environmental stresses, drought and famine. Notably, drought-induced water deprivation is associated with dehydration anorexia and thus a concomitant potential nutrient stress. Our laboratory has performed studies among pregnant rat and sheep in which we simulate drought conditions via maternal dehydration and famine conditions via nutrient restriction. Maternal dehydration results in low-birth-weight offspring, which demonstrate gender-specific plasma hypernatremia and hypertonicity and arterial hypertension. Gestational nutrient restriction also resulted in low-birth-weight offspring. If permitted rapid catch-up growth by nutrient availability, these offspring demonstrate evidence of increased body weight and body fat, and leptin resistance as adults. Conversely, if the catch-up growth is delayed by nutrition restriction, the offspring exhibit normal body weight, body fat, and plasma leptin levels as adults. These studies indicate that osmoregulatory and cardiovascular homeostasis and phenotypic predisposition to obesity may be programmed in utero. Importantly, these results suggest that programming effects may be either potentiated or prevented by interventions during the neonatal period.
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Affiliation(s)
- Michael G Ross
- Department of Obstetrics and Gynecology, Harbor-UCLA Medical Center, 1000 W. Carson St., Box 3, Torrance, CA 90509, USA.
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26
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Brooks VL, Qi Y, O'Donaughy TL. Increased osmolality of conscious water-deprived rats supports arterial pressure and sympathetic activity via a brain action. Am J Physiol Regul Integr Comp Physiol 2005; 288:R1248-55. [PMID: 15661967 DOI: 10.1152/ajpregu.00638.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To test the hypothesis that high osmolality acts in the brain to chronically support mean arterial pressure (MAP) and lumbar sympathetic nerve activity (LSNA), the osmolality of blood perfusing the brain was reduced in conscious water-deprived and water-replete rats by infusion of hypotonic fluid via bilateral nonoccluding intracarotid catheters. In water-deprived rats, the intracarotid hypotonic infusion, estimated to lower osmolality by approximately 2%, decreased MAP by 9+/-1 mmHg and LSNA to 86+/-7% of control; heart increased by 25+/-8 beats per minute (bpm) (all P<0.05). MAP, LSNA, and heart rate did not change when the hypotonic fluid was infused intravenously. The intracarotid hypotonic fluid infusion was also ineffective in water-replete rats. Prior treatment with a V1 vasopressin antagonist did not alter the subsequent hypotensive and tachycardic effects of intracarotid hypotonic fluid infusion in water-deprived rats. In summary, acute decreases in osmolality of the carotid blood of water-deprived, but not water-replete, rats decreases MAP and LSNA and increases heart rate. These data support the hypothesis that the elevated osmolality induced by water deprivation acts via a region perfused by the carotid arteries, presumably the brain, to tonically increase MAP and LSNA and suppress heart rate.
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Affiliation(s)
- Virginia L Brooks
- Dept. of Physiology and Pharmacology, L-334, Oregon Health & Science Univ., 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA.
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Catanozi S, Rocha JC, Passarelli M, Guzzo ML, Alves C, Furukawa LNS, Nunes VS, Nakandakare ER, Heimann JC, Quintão ECR. Dietary sodium chloride restriction enhances aortic wall lipid storage and raises plasma lipid concentration in LDL receptor knockout mice. J Lipid Res 2003; 44:727-32. [PMID: 12562870 DOI: 10.1194/jlr.m200330-jlr200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study aimed at measuring the influence of a low salt diet on the development of experimental atherosclerosis in moderately hyperlipidemic mice. Experiments were carried out on LDL receptor (LDLR) knockout (KO) mice, or apolipoprotein E (apoE) KO mice on a low sodium chloride diet (LSD) as compared with a normal salt diet (NSD). On LSD, the rise of the plasma concentrations of TG and nonesterified fatty acid (NEFA) was, respectively, 19% and 34% in LDLR KO mice, and 21% and 35% in apoE KO mice, and that of plasma cholesterol was limited to the LDLR KO group alone (15%). Probably due to the apoE KO severe hypercholesterolemia, the arterial inner-wall fat storage was not influenced by the diet salt content and was far more abundant in the apoE KO than in the LDLR KO mice. However, in the less severe hypercholesterolemia of the LDLR KO mice, lipid deposits on the LSD were greater than on the NSD. Arterial fat storage correlated with NEFA concentrations in the LDLR KO mice alone (n = 14, P = 0.0065). Thus, dietary sodium chloride restriction enhances aortic wall lipid storage in moderately hyperlipidemic mice.
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Affiliation(s)
- Sérgio Catanozi
- Lipids Laboratory (LIM 10), University of São Paulo Medical School, Brazil
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Toney GM, Chen QH, Cato MJ, Stocker SD. Central osmotic regulation of sympathetic nerve activity. ACTA PHYSIOLOGICA SCANDINAVICA 2003; 177:43-55. [PMID: 12492778 DOI: 10.1046/j.1365-201x.2003.01046.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIM In this review, we will focus on the central neural mechanisms that couple osmotic perturbations to changes in sympathetic nerve discharge, and the possible impact these actions have in cardiovascular diseases such as arterial hypertension and congestive heart failure. RESULTS Changes in extracellular fluid osmolality lead to specific regulatory responses in defence of body fluid and cardiovascular homeostasis. Systemic hyperosmolality is well known to stimulate thirst and the release of antidiuretic hormone. These responses are largely due to osmosensing neurones in the forebrain lamina terminalis and hypothalamus and are critical elements in a control system that operates to restore body fluid osmolality. An equally important, but less characterized, target of central osmoregulatory processes is the sympathetic nervous system. CONCLUSION Understanding the neurobiology of sympathetic responses to changes in osmolality has important implications for body fluid and cardiovascular physiology. By stabilizing osmolality, vascular volume is preserved and thereby relatively normal levels of cardiac output and arterial pressure are maintained.
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Affiliation(s)
- G M Toney
- Department of Physiology: MC 7756, The University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
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Kagota S, Tamashiro A, Yamaguchi Y, Nakamura K, Kunitomo M. High salt intake impairs vascular nitric oxide/cyclic guanosine monophosphate system in spontaneously hypertensive rats. J Pharmacol Exp Ther 2002; 302:344-51. [PMID: 12065736 DOI: 10.1124/jpet.302.1.344] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In aortas of spontaneously hypertensive rats (SHRs), excessive dietary salt causes down-regulation of soluble guanylate cyclase (sGC) followed by decreased cyclic GMP production, which leads to impairment of the vascular relaxation response to nitric oxide (NO). The present study aimed to elucidate whether this impaired NO/cyclic GMP system results secondarily from increased blood pressure or from an effect of the salt itself. The antihypertensive drug nifedipine was used on 4-week-old SHRs that received a normal-salt diet or a high-salt diet for 4 weeks. Treatment with nifedipine (30 mg/kg/day, p.o.) reduced the increased blood pressure of SHRs fed the high-salt diet to the level of SHRs fed the normal-salt diet. In aortic rings from SHRs fed the high-salt diet, not only endothelium-dependent relaxations but also endothelium-independent relaxations were significantly impaired. However, these impairments were not alleviated by treatment with nifedipine. Furthermore, nifedipine did not prevent the increase in protein levels of endothelial NO synthase and the decrease in the protein levels of sGC in aortas from SHRs fed the high-salt diet. These alterations by high salt intake were restored after replacement with the normal-salt diet for 4 additional weeks. These results indicate that in SHRs given excessive dietary salt, normalization of salt intake but not blood pressure reduction can ameliorate alterations in the NO/cyclic GMP system. High salt intake may directly affect the vascular smooth muscle and cause impairment of the relaxation response to NO.
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MESH Headings
- Animals
- Aorta, Thoracic/drug effects
- Blood Pressure/drug effects
- Blood Vessels/physiology
- Body Weight/drug effects
- Calcium Channel Blockers/pharmacology
- Cyclic GMP/physiology
- Endothelium, Vascular/drug effects
- Heart Rate/drug effects
- Male
- Muscle Relaxation/drug effects
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Nifedipine/pharmacology
- Nitric Oxide/blood
- Nitric Oxide/physiology
- Nitric Oxide Synthase/biosynthesis
- Nitric Oxide Synthase/genetics
- Nitric Oxide Synthase Type III
- Rats
- Rats, Inbred SHR
- Sodium Chloride, Dietary/adverse effects
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Affiliation(s)
- Satomi Kagota
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Koshien Kyuban-cho, Nishinomiya 663-8179, Japan.
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