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Fioretti AC, Dsouki NA, do Vale B, de Carvalho RP, Dias DPM, Venancio DP, Fonseca FLA, Sato MA. Vitamin D supplementation at different doses affects the vagal component of the baroreceptor reflex and the Bezold-Jarisch reflex in eutrophic rats. Front Physiol 2022; 13:934625. [PMID: 35991180 PMCID: PMC9389110 DOI: 10.3389/fphys.2022.934625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 07/05/2022] [Indexed: 11/13/2022] Open
Abstract
Vitamin D has been used to prevent several diseases. The 1,25 (OH) 2D3, the active form of vitamin D (VitD), participates in calcium metabolism, and has direct action in various tissues as those of the cardiovascular system binding to the VitD receptor. We investigated whether the supplementation with different doses of VitD affect or not the resting mean arterial pressure (MAP) and heart rate (HR), heart rate variability (HRV), baroreceptor and Bezold-Jarisch reflexes in eutrophic rats. Adult male Wistar rats were randomly assigned in 4 groups (Control, VitD 15, 250, and 3,750 IU/day, n = 6/group). After 3 days of supplementation, MAP and HR recordings were performed in freely moving rats. Baseline (resting) MAP, HR, and HRV showed no difference in Control and VitD groups. Nevertheless, the index of the baroreceptor reflex showed that the bradycardic component of the baroreflex evoked by a pressor dose of phenylephrine (3 μg/kg of b.w.) in bolus injection had a significant increase in rats supplemented with VitD 15 IU/day for 3 days compared to Control animals. No difference was observed in the index of the baroreflex evaluated with phenylephrine in rats treated with VitD 250 and 3,750 IU/day for 3 days in comparison to the Control group. The index of the baroreceptor reflex evaluated with an intravenous bolus injection of a depressor dose of sodium nitroprusside (30 μg/kg of b.w.) showed that the tachycardic component of the baroreflex is not different comparing all groups supplemented with VitD and Control animals. Rats supplemented with VitD 15 IU/day presented exaggerated bradycardic responses to the intravenous injection of phenylbiguanide (PBG, 5 μg/kg of b.w.) compared to Control animals, despite the similar hypotension in both groups. Higher doses of supplementation of VitD (250 and 3,750 IU/day for 3 days) abolished the hypotension and bradycardia induced by PBG. The findings suggest that the supplementation with different doses of VitD (15, 250, and 3,750 IU/day) for 3 days did not affect the resting arterial pressure, heart rate and autonomic modulation on the heart in rats. Despite that, the supplementation with a low dose of VitD (15 IU/day for 3 days) improved the sensitivity of the bradycardic component of the baroreflex, whereas higher doses of supplementation with VitD (250 and 3,750 IU/day for 3 days) were unable to cause such effect. In addition, the Bezold-Jarisch reflex responses can be affected regardless the dose of VitD (15, 250 or 3,750 IU/day) supplementation for 3 days in rats.
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Affiliation(s)
- Alexandre C. Fioretti
- Department of Morphology and Physiology, Centro Universitario FMABC, Santo Andre, Brazil
| | - Nuha A. Dsouki
- Department of Morphology and Physiology, Centro Universitario FMABC, Santo Andre, Brazil
| | - Barbara do Vale
- Department of Morphology and Physiology, Centro Universitario FMABC, Santo Andre, Brazil
| | - Rodrigo P. de Carvalho
- Department of Morphology and Physiology, Centro Universitario FMABC, Santo Andre, Brazil
| | | | - Daniel P. Venancio
- Department of Morphology and Physiology, Centro Universitario FMABC, Santo Andre, Brazil
| | - Fernando L. A. Fonseca
- Laboratory of Clinical Analysis, Department of Pathology, Centro Universitario FMABC, Santo Andre, Brazil
| | - Monica A. Sato
- Department of Morphology and Physiology, Centro Universitario FMABC, Santo Andre, Brazil
- *Correspondence: Monica A. Sato,
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Zambrano LI, Pontes RB, Garcia ML, Nishi EE, Nogueira FN, Higa EMS, Cespedes JG, Bergamaschi CT, Campos RR. Pattern of sympathetic vasomotor activity in a model of hypertension induced by nitric oxide synthase blockade. Physiol Rep 2020; 7:e14183. [PMID: 31325242 PMCID: PMC6642275 DOI: 10.14814/phy2.14183] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 06/26/2019] [Accepted: 06/27/2019] [Indexed: 12/12/2022] Open
Abstract
We aimed to investigate the effects of nitric oxide (NO) synthesis inhibition by NO synthase inhibitor N‐nitro‐L‐arginine‐methyl ester (L‐NAME) treatment on the sympathetic vasomotor nerve activity (SNA) on two sympathetic vasomotor nerves, the renal and splanchnic. NO plasma level and systemic oxidative stress were assessed. Hypertension was induced by L‐NAME (20 mg/kg per day, by gavage, for seven consecutive days) in male Wistar rats. At the end of the treatment, blood pressure, heart rate, arterial baroreflex sensitivity, renal SNA (rSNA), and splanchnic SNA (sSNA) were assessed in urethane anesthetized rats. L‐NAME‐treated rats presented increased blood pressure (152 ± 2 mmHg, n = 17) compared to the control group (101 ± 2 mmHg, n = 15). Both rSNA (147 ± 10, n = 15 vs. 114 ± 5 Spikes/s, n = 9) and sSNA (137 ± 13, n = 14 vs. 74 ± 13 spikes/s, n = 9) were significantly increased in the L‐NAME‐treated compared to the control group. A differential response on baroreflex sensitivity was found, with a significant reduction for rSNA but not for sSNA arterial baroreceptor sensitivity in L‐NAME‐treated rats. The adjusted regression model revealed that the reduction of systemic NO levels partially explains the variation in sSNA and blood pressure, but not rSNA. Taken together, our data show that hypertension induced by NO synthase blockade is characterized by increased SNA to the rSNA and sSNA. In addition, we found that the rats that had the greatest reduction in NO levels in plasma by L‐NAME were those that developed higher blood pressure levels. The reduction in the NO level partially explains the variations in sSNA but not in rSNA.
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Affiliation(s)
- Lysien I Zambrano
- Department of Physiology, Cardiovascular Division, Escola Paulista de Medicina-Universidade Federal de São Paulo, São Paulo, Brazil.,Department of Morphology, School of Medical Sciences, National Autonomous University of Honduras, Tegucigalpa, Honduras
| | - Roberto B Pontes
- Department of Physiology, Cardiovascular Division, Escola Paulista de Medicina-Universidade Federal de São Paulo, São Paulo, Brazil
| | - Michelle L Garcia
- Department of Physiology, Cardiovascular Division, Escola Paulista de Medicina-Universidade Federal de São Paulo, São Paulo, Brazil
| | - Erika E Nishi
- Department of Physiology, Cardiovascular Division, Escola Paulista de Medicina-Universidade Federal de São Paulo, São Paulo, Brazil
| | - Fernando N Nogueira
- Departamento de Biomateriais e Biologia Oral, Faculdade de Odontologia, Universidade de São Paulo, São Paulo, Brazil
| | - Elisa M S Higa
- Nephrology Division, Escola Paulista de Medicina Universidade Federal de São Paulo, São Paulo, Brazil
| | - Juliana G Cespedes
- Institute of Science and Technology, Universidade Federal de São Paulo, São Jose dos Campos, Brazil
| | - Cassia T Bergamaschi
- Department of Physiology, Cardiovascular Division, Escola Paulista de Medicina-Universidade Federal de São Paulo, São Paulo, Brazil
| | - Ruy R Campos
- Department of Physiology, Cardiovascular Division, Escola Paulista de Medicina-Universidade Federal de São Paulo, São Paulo, Brazil
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Domingos-Souza G, Santos-Almeida FM, Meschiari CA, Ferreira NS, Pereira CA, Martinez D, Dias DPM, Silva LEV, Castania JA, Tostes RC, Fazan R. Electrical stimulation of the carotid sinus lowers arterial pressure and improves heart rate variability in L-NAME hypertensive conscious rats. Hypertens Res 2020; 43:1057-1067. [PMID: 32358534 DOI: 10.1038/s41440-020-0448-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 03/03/2020] [Accepted: 03/26/2020] [Indexed: 11/09/2022]
Abstract
We evaluated the effects of long-term (48 h) electrical stimulation of the carotid sinus (CS) in hypertensive rats. L-NAME-treated (10 days) Wistar rats were implanted with a catheter in the femoral artery and a miniaturized electrical stimulator attached to electrodes positioned around the left CS, encompassing the CS nerve. One day after implantation, arterial pressure (AP) was directly recorded in conscious animals for 60 min. Square pulses (1 ms, 3 V, 30 Hz) were applied intermittently (20/20 s ON/OFF) to the CS for 48 h. After the end of stimulation, AP was recorded again. Nonstimulated rats (control group) and rats without electrodes around the CS (sham-operated) were also studied. Next, the animals were decapitated, and segments of mesenteric resistance arteries were removed to study vascular function. After the stimulation period, AP was 16 ± 5 mmHg lower in the stimulated group, whereas sham-operated and control rats showed similar AP between the first and second recording periods. Heart rate variability (HRV) evaluated using time and frequency domain tools and a nonlinear approach (symbolic analysis) suggested that hypertensive rats with electrodes around the CS, stimulated or not, exhibited a shift in cardiac sympathovagal balance towards parasympathetic tone. The relaxation response to acetylcholine in endothelium-intact mesenteric arteries was enhanced in rats that underwent CS stimulation for 48 h. In conclusion, long-term CS stimulation is effective in reducing AP levels, improving HRV and increasing mesenteric vascular relaxation in L-NAME hypertensive rats. Moreover, only the presence of electrodes around the CS is effective in eliciting changes in HRV similar to those observed in stimulated rats.
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Affiliation(s)
- Gean Domingos-Souza
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil. .,Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, 65211, USA.
| | | | - César Arruda Meschiari
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.,Health and Sports Science Center, Federal University of Acre, Rio Branco, AC, Brazil
| | - Nathanne S Ferreira
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Camila A Pereira
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Diana Martinez
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, 65211, USA
| | | | - Luiz Eduardo Virgílio Silva
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Jaci Airton Castania
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Rita C Tostes
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Rubens Fazan
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
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Santos-Almeida FM, Domingos-Souza G, Meschiari CA, Fávaro LC, Becari C, Castania JA, Lopes A, Cunha TM, Moraes DJA, Cunha FQ, Ulloa L, Kanashiro A, Tezini GCSV, Salgado HC. Carotid sinus nerve electrical stimulation in conscious rats attenuates systemic inflammation via chemoreceptor activation. Sci Rep 2017; 7:6265. [PMID: 28740186 PMCID: PMC5524712 DOI: 10.1038/s41598-017-06703-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 06/16/2017] [Indexed: 01/23/2023] Open
Abstract
Recent studies demonstrated a critical functional connection between the autonomic (sympathetic and parasympathetic) nervous and the immune systems. The carotid sinus nerve (CSN) conveys electrical signals from the chemoreceptors of the carotid bifurcation to the central nervous system where the stimuli are processed to activate sympathetic and parasympathetic efferent signals. Here, we reported that chemoreflex activation via electrical CSN stimulation, in conscious rats, controls the innate immune response to lipopolysaccharide attenuating the plasma levels of inflammatory cytokines such as tumor necrosis factor (TNF), interleukin 1β (IL-1β) and interleukin 6 (IL-6). By contrast, the chemoreflex stimulation increases the plasma levels of anti-inflammatory cytokine interleukin 10 (IL-10). This chemoreflex anti-inflammatory network was abrogated by carotid chemoreceptor denervation and by pharmacological blockade of either sympathetic - propranolol - or parasympathetic - methylatropine – signals. The chemoreflex stimulation as well as the surgical and pharmacological procedures were confirmed by real-time recording of hemodynamic parameters [pulsatile arterial pressure (PAP) and heart rate (HR)]. These results reveal, in conscious animals, a novel mechanism of neuromodulation mediated by the carotid chemoreceptors and involving both the sympathetic and parasympathetic systems.
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Affiliation(s)
| | - Gean Domingos-Souza
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - César A Meschiari
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Laura Campos Fávaro
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Christiane Becari
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Jaci A Castania
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Alexandre Lopes
- Department of Pharmacology, Medical School of Ribeirão Preto - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Thiago M Cunha
- Department of Pharmacology, Medical School of Ribeirão Preto - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Davi J A Moraes
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Fernando Q Cunha
- Department of Pharmacology, Medical School of Ribeirão Preto - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Luis Ulloa
- Center of Immunology and Inflammation. Rutgers- New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Alexandre Kanashiro
- Department of Pharmacology, Medical School of Ribeirão Preto - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Geisa C S V Tezini
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil
| | - Helio C Salgado
- Department of Physiology, Ribeirão Preto Medical School - University of São Paulo, Ribeirão, Preto, 14049-900, Brazil.
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CHASWAL M, DAS S, PRASAD J, KATYAL A, FAHIM M. Chemical Sympathectomy Restores Baroreceptor-Heart Rate Reflex and Heart Rate Variability in Rats With Chronic Nitric Oxide Deficiency. Physiol Res 2015; 64:459-66. [DOI: 10.33549/physiolres.932804] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Nitric oxide (NO) plays a crucial role not only in regulation of blood pressure but also in maintenance of cardiac autonomic tone and its deficiency induced hypertension is accompanied by cardiac autonomic dysfunction. However, underlying mechanisms are not clearly defined. We hypothesized that sympathetic activation mediates hemodynamic and cardiac autonomic changes consequent to deficient NO synthesis. We used chemical sympathectomy by 6-hydroxydopamine to examine the influence of sympathetic innervation on baroreflex sensitivity (BRS) and heart rate variability (HRV) of chronic NG-nitro-L-arginine methyl ester (L-NAME) treated adult Wistar rats. BRS was determined from heart rate responses to changes in systolic arterial pressure achieved by intravenous administration of phenylephrine and sodium nitroprusside. Time and frequency domain measures of HRV were calculated from 5-min electrocardiogram recordings. Chronic L-NAME administration (50 mg/kg per day for 7 days orally through gavage) in control rats produced significant elevation of blood pressure, tachycardia, attenuation of BRS for bradycardia and tachycardia reflex and fall in time as well as frequency domain parameters of HRV. Sympathectomy completely abolished the pressor as well as tachycardic effect of chronic L-NAME. In addition, BRS and HRV improved after removal of sympathetic influence in chronic L-NAME treated rats. These results support the concept that an exaggerated sympathetic activity is the principal mechanism of chronic L NAME hypertension and associated autonomic dysfunction.
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Affiliation(s)
| | | | | | | | - M. FAHIM
- Department of Physiology, Hamdard Institute of Medical Sciences & Research, Jamia Hamdard, New Delhi, India
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da Silva TLTB, Mota MM, Fontes MT, Araújo JEDS, Carvalho VO, Bonjardim LR, Santos MRV. Effects of one resistance exercise session on vascular smooth muscle of hypertensive rats. Arq Bras Cardiol 2015; 105:160-7. [PMID: 26107814 PMCID: PMC4559125 DOI: 10.5935/abc.20150070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Revised: 03/12/2015] [Accepted: 03/23/2015] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Hypertension is a public health problem and increases the incidence of cardiovascular diseases. OBJECTIVE To evaluate the effects of a resistance exercise session on the contractile and relaxing mechanisms of vascular smooth muscle in mesenteric arteries of NG-nitro L-arginine methyl ester (L-NAME)-induced hypertensive rats. METHODS Wistar rats were divided into three groups: control (C), hypertensive (H), and exercised hypertensive (EH). Hypertension was induced by administration of 20 mg/kg of L-NAME for 7 days prior to experimental protocols. The resistance exercise protocol consisted of 10 sets of 10 repetitions and intensity of 40% of one repetition maximum. The reactivity of vascular smooth muscle was evaluated by concentration‑response curves to phenylephrine (PHEN), potassium chloride (KCl) and sodium nitroprusside (SNP). RESULTS Rats treated with L-NAME showed an increase (p < 0.001) in systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) compared to the initial period of induction. No difference in PHEN sensitivity was observed between groups H and EH. Acute resistance exercise reduced (p < 0.001) the contractile response induced by KCl at concentrations of 40 and 60 mM in group EH. Greater (p < 0.01) smooth muscle sensitivity to NPS was observed in group EH as compared to group H. CONCLUSION One resistance exercise session reduces the contractile response induced by KCl in addition to increasing the sensitivity of smooth muscle to NO in mesenteric arteries of hypertensive rats.
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da Silva AA, do Carmo JM, Dubinion JH, Bassi M, Mokhtarpouriani K, Hamza SM, Hall JE. Chronic central nervous system MC3/4R blockade attenuates hypertension induced by nitric oxide synthase inhibition but not by angiotensin II infusion. Hypertension 2014; 65:171-7. [PMID: 25287400 DOI: 10.1161/hypertensionaha.114.03999] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We examined whether central melanocortin 3 and 4 receptor (MC3/4R) blockade attenuates the blood pressure (BP) responses to chronic L-NAME or angiotensin II (Ang II) infusion in Sprague-Dawley rats implanted with telemetry transmitters, venous catheters, and intracerebroventricular cannula into the lateral ventricle. After 5 days of control measurements, L-NAME (10 μg/kg/min IV, groups 1 and 2) or Ang II (10 ng/kg/min IV, groups 3 and 4) were infused for 24 days, and starting on day 7 of L-NAME or Ang II infusion, the MC3/4R antagonist SHU-9119 (24 nmol/d, n=6/group; groups 1 and 3) or vehicle (saline 0.5 μL/h, n=6/group; groups 2 and 4) was infused intracerebroventricularly for 10 days. A control normotensive group also received SHU-9119 for 10 days (n=5). L-NAME and Ang II increased BP by 40±3 and 56±5 mm Hg, respectively, although heart rate was slightly reduced. MC3/4R blockade doubled food intake and reduced heart rate (≈40 to ≈50 bpm) in all groups. MC3/4R blockade caused only a small reduction in BP in normotensive group (4 mm Hg) and no change in rats receiving Ang II, although markedly reducing BP by 21±4 mm Hg in L-NAME-treated rats. After SHU-9119 infusion was stopped, food intake, heart rate, and BP gradually returned to values observed before SHU-9119 infusion was started. Ganglionic blockade at the end of L-NAME or Ang II infusion caused similar BP reduction in both groups. These results suggest that the brain MC3/4R contributes, at least in part, to the hypertension induced by chronic L-NAME infusion but not by Ang II.
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Affiliation(s)
- Alexandre A da Silva
- From the Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Center of Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson.
| | - Jussara M do Carmo
- From the Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Center of Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson
| | - John H Dubinion
- From the Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Center of Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson
| | - Mirian Bassi
- From the Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Center of Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson
| | - Kasra Mokhtarpouriani
- From the Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Center of Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson
| | - Shereen M Hamza
- From the Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Center of Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson
| | - John E Hall
- From the Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Center of Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson
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Arginine NO-dependent and NO-independent effects on hemodynamics. Eur J Pharmacol 2014; 729:138-43. [PMID: 24530418 DOI: 10.1016/j.ejphar.2014.01.070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 01/20/2014] [Accepted: 01/24/2014] [Indexed: 10/25/2022]
Abstract
L-arginine administration decreases mean arterial blood pressure (MABP), presumably by excess nitric oxide (NO) synthesis. However, some reports indicate that d-arginine, not a substrate of NO synthase (NOS), also induces hypotension. To clarify this phenomenon, the hemodynamic effects of L- and D-arginine and their modification by NOS inhibition with L-nitroarginine methyl ester (L-NAME) were assessed. MABP, cardiac output, stroke volume, heart rate and systemic vascular resistance were recorded in Sprague-Dawley rats under urethane or ketamine/diazepam anesthesia, with or without blockade of NO synthesis by L-NAME. Both stereoisomers of arginine induced a dose-related drop in MABP of similar magnitude and time course, but recovery from hypotension was slower in L-arginine than in D-arginine. The hypotension induced by both stereoisomers was due to a decrease in systemic vascular resistance (SVR) with increase in cardiac output (CO) and stroke volume (SV). Administration of L-NAME induced a pronounced increase in MABP and SVR, with decreases in CO and heart rate (HR). Infusion of L-arginine after L-NAME significantly decreased MABP and SVR at the highest dose while d-arginine failed to do so. After L-NAME, MABP was significantly lower under l-arginine than under d-arginine at all doses. These experiments suggest a dual mechanism in the hypotensive effect of L-arginine: a NO independent action on vascular resistance shared with D-arginine, and a NO dependent mechanism that becomes evident in the presence of NOS inhibition with L-NAME. Cardiac effects of NO do not appear to play a role in L-arginine hypotension.
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Burke SL, Lambert E, Head GA. New Approaches to Quantifying Sympathetic Nerve Activity. Curr Hypertens Rep 2011; 13:249-57. [DOI: 10.1007/s11906-011-0196-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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10
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Durand MDT, Castania JA, Fazan R, Salgado MCO, Salgado HC. Hemodynamic responses to aortic depressor nerve stimulation in conscious l-NAME-induced hypertensive rats. Am J Physiol Regul Integr Comp Physiol 2011; 300:R418-27. [DOI: 10.1152/ajpregu.00463.2010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study investigated whether baroreflex control of autonomic function is impaired when there is a deficiency in NO production and the role of adrenergic and cholinergic mechanisms in mediating reflex responses. Electrical stimulation of the aortic depressor nerve in conscious normotensive and nitro-l-arginine methyl ester (l-NAME)-induced hypertensive rats was applied before and after administration of methylatropine, atenolol, and prazosin alone or in combination. The hypotensive response to progressive electrical stimulation (5 to 90 Hz) was greater in hypertensive (−27 ± 2 to −64 ± 3 mmHg) than in normotensive rats (−17 ± 1 to −46 ± 2 mmHg), whereas the bradycardic response was similar in both groups (−34 ± 5 to −92 ± 9 and −21 ± 2 to −79 ± 7 beats/min, respectively). Methylatropine and atenolol showed no effect in the hypotensive response in either group. Methylatropine blunted the bradycardic response in both groups, whereas atenolol attenuated only in hypertensive rats. Prazosin blunted the hypotensive response in both normotensive (43%) and hypertensive rats (53%) but did not affect the bradycardic response in either group. Prazosin plus angiotensin II, used to restore basal arterial pressure, provided hemodynamic responses similar to those of prazosin alone. The triple pharmacological blockade abolished the bradycardic response in both groups but displayed similar residual hypotensive response in hypertensive (−13 ± 2 to −27 ± 2 mmHg) and normotensive rats (−10 ± 1 to −25 ± 3 mmHg). In conclusion, electrical stimulation produced a well-preserved baroreflex-mediated decrease in arterial pressure and heart rate in conscious l-NAME-induced hypertensive rats. Moreover, withdrawal of the sympathetic drive played a role in the reflex bradycardia only in hypertensive rats. The residual fall in pressure after the triple pharmacological blockade suggests the involvement of a vasodilatory mechanism unrelated to NO or deactivation of α1-adrenergic receptor.
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Mastelari RB, de Souza HCD, Lenhard A, de Aguiar Corrêa FM, Martins-Pinge MC. Nitric oxide inhibition in paraventricular nucleus on cardiovascular and autonomic modulation after exercise training in unanesthetized rats. Brain Res 2010; 1375:68-76. [PMID: 21172321 DOI: 10.1016/j.brainres.2010.12.049] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2010] [Revised: 10/30/2010] [Accepted: 12/13/2010] [Indexed: 10/18/2022]
Abstract
It is well known that regular physical exercise alter cardiac function and autonomic modulation of heart rate variability (HRV). The paraventricular nucleus of hypothalamus (PVN) is an important site of integration for autonomic and cardiovascular responses, where nitric oxide (NO) plays an important role. The aim of our study was to evaluate the cardiovascular parameters and autonomic modulation by means of spectral analysis after nitric oxide synthase (NOS) inhibition in the PVN in conscious sedentary (S) or swimming trained (ST) rats. After swimming training protocol, adult male Wistar rats, instrumented with guide cannulas to PVN and femoral artery and vein catheters were submitted to mean arterial pressure (MAP) and heart rate (HR) recording. At baseline, the physical training induced a resting bradycardia (S: 374±5, ST: 346±1bpm) and promoted adaptations in HRV characterized by an increase in high-frequency oscillations (HF; 26.43±6.91 to 88.96±2.44) and a decrease in low-frequency oscillations (LF; 73.57±6.91 to 11.04±2.44) in normalized units. The microinjection of N(ω)-nitro-l-arginine methyl ester (l-NAME) in the PVN of sedentary and trained rats promoted increase in MAP and HR. l-NAME in the PVN did not significantly alter the spectral parameters of HRV of sedentary animals, however in the trained rats increased LF oscillations (11.04±2.44 to 27.62±6.97) and decreased HF oscillations (88.96±2.44 to 72.38±6.97) in normalized units compared with baseline. Our results suggest that NO in the PVN may collaborate to cardiac autonomic modulation after exercise training.
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Affiliation(s)
- Rosiane Batista Mastelari
- Department of Physiological Sciences, Center of Biological Sciences, State University of Londrina, Londrina, Paraná, Brazil
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