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Tchekalarova J, Ivanova P, Krushovlieva D. Age-Related Effects of AT1 Receptor Antagonist Losartan on Cognitive Decline in Spontaneously Hypertensive Rats. Int J Mol Sci 2024; 25:7340. [PMID: 39000445 PMCID: PMC11242852 DOI: 10.3390/ijms25137340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2024] [Revised: 06/21/2024] [Accepted: 06/30/2024] [Indexed: 07/16/2024] Open
Abstract
Both hypertension and aging are known to increase the vulnerability of the brain to neurovascular damage, resulting in cognitive impairment. The present study investigated the efficacy of the antihypertensive drug losartan on age- and hypertension-associated cognitive decline and the possible mechanism underlying its effect in spontaneously hypertensive rats (SHRs). Losartan was administered (10 mg/kg, i.p. for 19 days) to 3- and 14-month-old SHRs. Age-matched Wistar rats were used as controls. Working memory, short-term object recognition, and spatial memory were assessed using the Y-maze, object recognition test (ORT) and radial arm maze (RAM) test. The expression of markers associated with aging, oxidative stress, and memory-related signaling was assessed in the frontal cortex (FC) and hippocampus. Motor activity measured over 24 h was not different between groups. Middle-aged vehicle-treated SHRs showed poorer performance in spontaneous alternation behavior (SAB) and activity in the first Y-maze test than their younger counterparts, suggesting age-related reduced "decision making" and reactivity in a novel environment. Losartan improved the age- and hypertension-induced decline in short-term recognition and spatial memory measured in the ORT and the second Y-maze test, particularly in the middle-aged rats, but was ineffective in the young adult rats. Changes in memory and age-related markers such as cAMP response element-binding protein (CREB) and amyloid-β1-42 (Aβ1-42) and increased oxidative stress were observed in the hippocampus but not in the FC between young adult and middle-aged vehicle-treated SHRs. Losartan increased CREB expression while reducing Aβ1-42 levels and concomitant oxidative stress in middle-aged SHRs compared with vehicle-treated SHRs. In conclusion, our study highlights the complex interplay between hypertension, aging, and cognitive impairment. It suggests that there is a critical time window for therapeutic intervention with angiotensin II type 1 receptor blockers.
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Affiliation(s)
- Jana Tchekalarova
- Department of Behavioral Neurobiology, Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria; (P.I.); (D.K.)
- Department of Organic Chemistry, University of Chemical Technology and Metallurgy, 1756 Sofia, Bulgaria
| | - Petja Ivanova
- Department of Behavioral Neurobiology, Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria; (P.I.); (D.K.)
| | - Desislava Krushovlieva
- Department of Behavioral Neurobiology, Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria; (P.I.); (D.K.)
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Vavřínová A, Behuliak M, Vodička M, Bencze M, Ergang P, Vaněčková I, Zicha J. More efficient adaptation of cardiovascular response to repeated restraint in spontaneously hypertensive rats: the role of autonomic nervous system. Hypertens Res 2024:10.1038/s41440-024-01765-w. [PMID: 38956283 DOI: 10.1038/s41440-024-01765-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 05/15/2024] [Accepted: 06/06/2024] [Indexed: 07/04/2024]
Abstract
We hypothesized that sympathetic hyperactivity and parasympathetic insuficiency in spontaneously hypertensive rats (SHR) underlie their exaggerated cardiovascular response to acute stress and impaired adaptation to repeated restraint stress exposure compared to Wistar-Kyoto rats (WKY). Cardiovascular responses to single (120 min) or repeated (daily 120 min for 1 week) restraint were measured by radiotelemetry and autonomic balance was evaluated by power spectral analysis of systolic blood pressure variability (SBPV) and heart rate variability (HRV). Baroreflex sensitivity (BRS) was measured by the pharmacological Oxford technique. Stress-induced pressor response and vascular sympathetic activity (low-frequency component of SBPV) were enhanced in SHR subjected to single restraint compared to WKY, whereas stress-induced tachycardia was similar in both strains. SHR exhibited attenuated cardiac parasympathetic activity (high-frequency component of HRV) and blunted BRS compared to WKY. Repeated restraint did not affect the stress-induced increase in blood pressure. However, cardiovascular response during the post-stress recovery period of the 7th restraint was reduced in both strains. The repeatedly restrained SHR showed lower basal heart rate during the dark (active) phase and slightly decreased basal blood pressure during the light phase compared to stress-naive SHR. SHR subjected to repeated restraint also exhibited attenuated stress-induced tachycardia, augmented cardiac parasympathetic activity, attenuated vascular sympathetic activity and improved BRS during the last seventh restraint compared to single-stressed SHR. Thus, SHR exhibited enhanced cardiovascular and sympathetic responsiveness to novel stressor exposure (single restraint) compared to WKY. Unexpectedly, the adaptation of cardiovascular and autonomic responses to repeated restraint was more effective in SHR.
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Affiliation(s)
- Anna Vavřínová
- Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
| | - Michal Behuliak
- Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
| | - Martin Vodička
- Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
| | - Michal Bencze
- Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
| | - Peter Ergang
- Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
| | - Ivana Vaněčková
- Institute of Physiology, Czech Academy of Sciences, Prague, Czechia
| | - Josef Zicha
- Institute of Physiology, Czech Academy of Sciences, Prague, Czechia.
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Katary M, Abdel-Rahman AA. Alcohol suppresses cardiovascular diurnal variations in male normotensive rats: Role of reduced PER2 expression and CYP2E1 hyperactivity in the heart. Alcohol 2020; 89:27-36. [PMID: 32777474 DOI: 10.1016/j.alcohol.2020.08.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/26/2020] [Accepted: 08/04/2020] [Indexed: 01/01/2023]
Abstract
BACKGROUND AND AIMS The molecular mechanism of the adverse effects of ethanol on diurnal cardiovascular regulation remains unknown. In separate studies, the cardiac circadian rhythm protein period-2 (PER2) confers cardioprotection and, in other organs, PER2 interaction with the ethanol-metabolizing enzyme CYP2E1 underlies, via heme oxygenase-1 (HO-1) upregulation, tissue injury/dysfunction. Here, we hypothesized that suppressed PER2 expression and elevated CYP2E1/HO-1 levels in the heart underlie the disrupted diurnal cardiovascular rhythm/function in alcohol-fed normotensive rats. METHODS In ethanol-fed (5%, w/v; 8 weeks) or isocaloric liquid diet-fed male rats, diurnal changes in blood pressure (BP), heart rate (HR), HR vagal variability index, root mean square of successive beat-to-beat differences in beat-interval duration (rMSSD), and cardiac function were measured by radiotelemetry and echocardiography followed by ex vivo molecular studies. RESULTS Radiotelemetry findings showed ethanol-evoked reductions in BP (during the dark cycle), rMSSD (during both cycles), and in diurnal differences in BP and rMSSD. Echocardiography findings revealed significant (p < 0.05) reductions in ejection fraction and fractional shortening (weeks 4-6) in the absence of cardiac remodeling (collagen content). Hearts of ethanol-fed rats exhibited higher (p < 0.05) CYP2E1 activity (50%) and HO-1 expression (63%), along with reduction (p < 0.05) in PER2 levels (29%), compared with the hearts of isocaloric diet-fed control rats. CONCLUSIONS Our novel findings implicate upregulations of CYP2E1/HO-1 and downregulation of the circadian rhythm cardioprotective protein PER2, in the heart, in the chronic deleterious diurnal cardiovascular effects of alcohol in male rats.
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Affiliation(s)
- Mohamed Katary
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Abdel A Abdel-Rahman
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, NC, United States.
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Li JY, Kuo TBJ, Yang CCH. Behaviour consistency is a sensitive tool for distinguishing the effects of aging on physical activity. Behav Brain Res 2020; 389:112619. [PMID: 32348871 DOI: 10.1016/j.bbr.2020.112619] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 02/24/2020] [Accepted: 03/15/2020] [Indexed: 11/16/2022]
Abstract
We attempted to establish a novel parameter of behaviour consistency to help determine the effect of age on physical activity. Using the speed of movement to quantify behaviour might not be sufficient to determine this effect. The slowing of motor activities that occurs with aging is related to the decline of the aging brain. Previous studies have found different running-related hippocampal theta rhythm responses in the aging and exercise model. Therefore, we hypothesized that a familiarity with the environment and physical strength affect behavioural consistency in rats during running exercises. For this study, we used a treadmill and 30-minute running test at constant speeds and compared changes in the triaxial accelerometer and hippocampal theta rhythm between adult and middle-aged rats. No significant differences in RR intervals, mean cross-correlations (MCCs), or the proportion of good correlation coefficient (PGCC) were observed between adult and middle-aged rats in awake states before running on the treadmill. The root mean square (RMS) of the triaxial acceleration vectors in middle-aged rats was higher than that in adult rats. In the treadmill running tests, the RMS observed in middle-aged rats was significantly lower than that observed in adult rats. MCC and PGCC, which indicate movement consistencies, were significantly higher in middle-aged rats than they were in adult rats during the entire running test. However, only the RMS of the adult rats showed a negative correlation with exercise duration. Both MCC and PGCC were positively correlated with exercise duration. By contrast, a similar phenomenon was not found in the changes or differences in hippocampal theta rhythms between these two groups. Therefore, we consider that the MCC and PGCC could distinguish age-related movement differences and indicate coordination/adaptation during exercise. Changes in physical activity and alterations in the hippocampal theta rhythm were not different between the groups.
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Affiliation(s)
- Jia-Yi Li
- Department of Health and Leisure Management, Yuanpei University of Medical Technology, Hsinchu, Taiwan; Sleep Research Center, National Yang-Ming University, Taipei, Taiwan
| | - Terry B J Kuo
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan; Digital Medicine Center, National Yang-Ming University, Taipei, Taiwan.
| | - Cheryl C H Yang
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan.
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Baka T, Simko F. Ivabradine reversed nondipping heart rate in rats with l-NAME-induced hypertension. Clin Exp Pharmacol Physiol 2019; 46:607-610. [PMID: 30790319 DOI: 10.1111/1440-1681.13075] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 02/15/2019] [Accepted: 02/18/2019] [Indexed: 12/13/2022]
Abstract
We hypothesized that decreasing elevated night-time heart rate (HR) in hypertension by administering a bradycardic agent (ivabradine) at bedtime could bring cardiovascular benefit. Since rats are nocturnal animals, they exhibit circadian rhythms phase-shifted relative to humans. Sixty-six Wistar rats were divided into non-diseased controls and rats with l-NAME-induced hypertension to compare the haemodynamic effects of daytime-dosed and night-time-dosed ivabradine. l-NAME-induced hypertension inverted the physiological 5.6% night-to-day HR dip to an undesirable HR rise by 11.1%. Ivabradine dosed at daytime (the rat's resting phase) reverted a night-to-day HR rise to HR dip by 14.2%. These results suggest a cardiovascular benefit of ivabradine dosed at the human's resting phase (night-time) for hypertensive patients with nondipping HR.
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Affiliation(s)
- Tomas Baka
- Institute of Pathophysiology, Faculty of Medicine, Comenius University, Bratislava, Slovak Republic
| | - Fedor Simko
- Institute of Pathophysiology, Faculty of Medicine, Comenius University, Bratislava, Slovak Republic.,3rd Department of Internal Medicine, Faculty of Medicine, Comenius University, Bratislava, Slovak Republic.,Institute of Experimental Endocrinology, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovak Republic
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6
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Cardiac Autonomic Neuropathy as a Result of Mild Hypercaloric Challenge in Absence of Signs of Diabetes: Modulation by Antidiabetic Drugs. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:9389784. [PMID: 29643979 PMCID: PMC5831709 DOI: 10.1155/2018/9389784] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 11/21/2017] [Accepted: 11/29/2017] [Indexed: 12/13/2022]
Abstract
Cardiac autonomic neuropathy (CAN) is an early cardiovascular complication of diabetes occurring before metabolic derangement is evident. The cause of CAN remains elusive and cannot be directly linked to hyperglycemia. Recent clinical data report cardioprotective effects of some antidiabetic drugs independent of their hypoglycemic action. Here, we used a rat model receiving limited daily increase in calories from fat (HC diet) to assess whether mild metabolic challenge led to CAN in absence of interfering effects of hyperglycemia, glucose intolerance, or obesity. Rats receiving HC diet for 12 weeks showed reduction in baroreceptor sensitivity and heart rate variability despite lack of change in baseline hemodynamic and cardiovascular structural parameters. Impairment of cardiac autonomic control was accompanied with perivascular adipose inflammation observed as an increased inflammatory cytokine expression, together with increased cardiac oxidative stress, and signaling derangement characteristic of diabetic cardiomyopathy. Two-week treatment with metformin or pioglitazone rectified the autonomic derangement and corrected the molecular changes. Switching rats to normal chow but not to isocaloric amounts of HC for two weeks reversed CAN. As such, we conclude that adipose inflammation due to increased fat intake might underlie development of CAN and, hence, the beneficial effects of metformin and pioglitazone.
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El-Yazbi AF, Ibrahim KS, El-Gowelli HM, El-Deeb NM, El-Mas MM. Modulation by NADPH oxidase of the chronic cardiovascular and autonomic interaction between cyclosporine and NSAIDs in female rats. Eur J Pharmacol 2017; 806:96-104. [DOI: 10.1016/j.ejphar.2017.04.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 04/11/2017] [Accepted: 04/13/2017] [Indexed: 12/23/2022]
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Ibrahim KS, El-Yazbi AF, El-Gowelli HM, El-Mas MM. Opposite Modulatory Effects of Selective and Non-Selective Cyclooxygenase Inhibition on Cardiovascular and Autonomic Consequences of Cyclosporine in Female Rats. Basic Clin Pharmacol Toxicol 2017; 120:571-581. [DOI: 10.1111/bcpt.12754] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 12/22/2016] [Indexed: 12/25/2022]
Affiliation(s)
- Karim S. Ibrahim
- Department of Pharmacology and Toxicology; Faculty of Pharmacy; Alexandria University; Alexandria Egypt
| | - Ahmed F. El-Yazbi
- Department of Pharmacology and Toxicology; Faculty of Pharmacy; Alexandria University; Alexandria Egypt
| | - Hanan M. El-Gowelli
- Department of Pharmacology and Toxicology; Faculty of Pharmacy; Alexandria University; Alexandria Egypt
| | - Mahmoud M. El-Mas
- Department of Pharmacology and Toxicology; Faculty of Pharmacy; Alexandria University; Alexandria Egypt
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9
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Lai CT, Chen CY, Kuo TBJ, Chern CM, Yang CCH. Sympathetic Hyperactivity, Sleep Fragmentation, and Wake-Related Blood Pressure Surge During Late-Light Sleep in Spontaneously Hypertensive Rats. Am J Hypertens 2016; 29:590-7. [PMID: 26350298 DOI: 10.1093/ajh/hpv154] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Accepted: 08/13/2015] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Many cardiovascular disease events occur before morning awaking and are more severe in hypertensive patients. Sleep-related cardiovascular regulation has been suggested to play an important role in the pathogenesis. In this study, we explored whether such impairments are exaggerated during late sleep (before the active phase) in spontaneously hypertensive rats (SHRs). METHODS Polysomnographic recording was performed through wireless transmission in freely moving SHRs and Wistar-Kyoto rats (WKYs) over 24 hours. The SHRs were injected with saline and an α1-adrenergic antagonist (prazosin: 5 mg/kg) on 2 separate days. Cardiovascular and autonomic functions were assessed by cardiovascular variability and spontaneous baroreflex analysis. RESULTS Compared with the early-light period (Zeitgeber time (ZT) 0-6 hours), both the WKYs and SHRs during the late-light period (ZT 6-12 hours) showed sleep fragmentation, sympathovagal imbalance, and baroreflex impairment, which were exaggerated and more advanced in the SHRs. Like the morning blood pressure (BP) surge in humans, we found that there was a wake-related blood pressure surge (WBPS) during the late-light period in both groups of rats. The WBPS was also greater and occurred earlier in the SHRs, and was accompanied by a surge in vascular sympathetic index. Under α1-adrenergic antagonism, the late-light period-related sleep fragmentation and BP surge in the SHRs were partially reversed. CONCLUSIONS Our results reveal that sleep-related sympathetic overactivity, baroreflex sensitivity impairment, WBPS, and sleep fragmentation in SHRs deteriorates during the late-light period can be partially alleviated by treatment with an α1-adrenoceptor antagonist.
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Affiliation(s)
- Chun-Ting Lai
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan
| | - Chun-Yu Chen
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan
| | - Terry B J Kuo
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan; Research Center for Adaptive Data Analysis, National Central University, Taoyuan, Taiwan; Chief of Division of Translational Medicine, Stroke & Neurovascular Center, Veterans General Hospital, Taipei, Taiwan
| | - Chang-Ming Chern
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Chief of Division of Translational Medicine, Stroke & Neurovascular Center, Veterans General Hospital, Taipei, Taiwan
| | - Cheryl C H Yang
- Sleep Research Center, National Yang-Ming University, Taipei, Taiwan; Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan; Department of Education and Research, Taipei City Hospital, Taipei, Taiwan;
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10
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The combination of valsartan and ramipril protects against blood vessel injury and lowers blood pressure. JOURNAL OF PHARMACEUTICAL INVESTIGATION 2016. [DOI: 10.1007/s40005-016-0241-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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11
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Central GABAA receptors are involved in inflammatory and cardiovascular consequences of endotoxemia in conscious rats. Naunyn Schmiedebergs Arch Pharmacol 2015; 389:279-88. [PMID: 26685896 DOI: 10.1007/s00210-015-1201-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 12/14/2015] [Indexed: 02/06/2023]
Abstract
γ-Aminobutyric acid (GABA), the principal brain inhibitory neurotransmitter, modulates inflammatory and neurodegenerative disease. Here, we tested the hypothesis that central GABAergic neurotransmission mediates the detrimental inflammatory, hemodynamic, and cardiac autonomic actions of endotoxemia. The effects of drugs that block GABA receptors or interfere with GABA uptake or degradation on blood pressure (BP), heart rate (HR), and HR variability (HRV) responses elicited by i.v. lipopolysaccharide (LPS) were assessed in conscious rats. The hypotensive effect of LPS (10 mg/kg) was blunted after intracisternal (i.c.) administration of bicuculline (GABAA receptor antagonist) or saclofen (GABAB receptor antagonist). By contrast, the concomitant LPS-evoked tachycardia and decreases in time domain and frequency domain indices of HRV (measures of cardiac autonomic control) were abolished upon treatment with bicuculline but not saclofen. Increases in serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) caused by LPS disappeared in the presence of bicuculline or saclofen, whereas LPS-evoked increases in serum nitric oxide metabolites (NOx) were counteracted by bicuculline only. None of the endotoxemia effects was altered in rats treated with i.c. tiagabine (GABA reuptake inhibitor) or vigabatrin (GABA transaminase inhibitor). These data suggest a major role for central GABAA receptors in the inflammatory and cardiovascular effects of endotoxemia.
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Brockway R, Tiesma S, Bogie H, White K, Fine M, O'Farrell L, Michael M, Cox A, Coskun T. Fully Implantable Arterial Blood Glucose Device for Metabolic Research Applications in Rats for Two Months. J Diabetes Sci Technol 2015; 9:771-81. [PMID: 26021562 PMCID: PMC4525668 DOI: 10.1177/1932296815586424] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Chronic continuous glucose monitoring options for animal research have been very limited due to various technical and biological challenges. We provide an evaluation of a novel telemetry device for continuous monitoring of temperature, activity, and plasma glucose levels in the arterial blood of rats for up to 2 months. METHODS In vivo testing in rats including oral glucose tolerance tests (OGTTs) and intraperitoneal glucose tolerance tests (IPGTTs) and ex vivo waterbath testing were performed to evaluate acute and chronic sensor performance. Animal studies were in accordance with the guidelines for the care and use of laboratory animals and approved by the corresponding animal care and use committees (Data Sciences International, Eli Lilly). RESULTS Results demonstrated the ability to record continuous measurements for 75 days or longer. Bench testing demonstrated a high degree of linearity over a range of 20-850 mg/dL with R(2) = .998 for linear fit and .999 for second order fit (n = 8 sensors). Evaluation of 6 rats over 28 days with 52 daily and OGTT test strip measurements each resulted in mean error of 3.8% and mean absolute relative difference of 16.6%. CONCLUSIONS This device provides significant advantages in the quality and quantity of data that can be obtained relative to existing alternatives such as intermittent blood sampling. These devices provide the opportunity to expand the understanding of both glucose metabolism and homeostasis and to work toward improved therapies and cures for diabetes.
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Affiliation(s)
| | - Scott Tiesma
- Data Sciences International, Inc (DSI), Saint Paul, MN, USA
| | - Heather Bogie
- Data Sciences International, Inc (DSI), Saint Paul, MN, USA
| | - Kimberly White
- Data Sciences International, Inc (DSI), Saint Paul, MN, USA
| | - Megan Fine
- Data Sciences International, Inc (DSI), Saint Paul, MN, USA
| | | | | | - Amy Cox
- Lilly Research Laboratories, Indianapolis, IN, USA
| | - Tamer Coskun
- Lilly Research Laboratories, Indianapolis, IN, USA
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A single exposure to acrolein desensitizes baroreflex responsiveness and increases cardiac arrhythmias in normotensive and hypertensive rats. Cardiovasc Toxicol 2014; 14:52-63. [PMID: 24078368 DOI: 10.1007/s12012-013-9228-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Short-term exposure to air pollutants has been linked to acute cardiovascular morbidity and mortality. Even in the absence of overt signs or symptoms, pollutants can cause subtle disruptions to internal compensatory mechanisms, which maintain homeostatic balance in response to various environmental and physiological stressors. We hypothesized that a single exposure to acrolein, a ubiquitous gaseous air pollutant, would decrease the sensitivity of baroreflex (BRS), which maintains blood pressure by altering heart rate (HR), modify cardiac electrophysiological properties and increase arrhythmia in rats. Wistar-Kyoto normotensive (WKY) and spontaneously hypertensive (SH) rats implanted with radiotelemeters and a chronic jugular vein catheter were tested for BRS using phenylephrine and sodium nitroprusside 2 days before and 1 h after whole-body exposure to 3 ppm acrolein (3 h). HR and electrocardiogram (ECG) were continuously monitored for the detection of arrhythmia in the pre-exposure, exposure and post-exposure periods. Whole-body plethysmography was used to continuously monitor ventilation in conscious animals. SH rats had higher blood pressure, lower BRS and increased frequency of AV block as evidence by non-conducted p-waves when compared with WKY rats. A single exposure to acrolein caused a decrease in BRS and increased incidence of arrhythmia in both WKY and SH rats. There were minimal ECG differences between the strains, whereas only SH rats experienced irregular breathing during acrolein. These results demonstrate that acrolein causes immediate cardiovascular reflexive dysfunction and persistent arrhythmia in both normal and hypertensive animals. As such, homeostatic imbalance may be one mechanism by which air pollution increases risk 24 h after exposure, particularly in people with underlying cardiovascular disease.
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Lewis BJ, Herrlinger KA, Craig TA, Mehring-Franklin CE, DeFreitas Z, Hinojosa-Laborde C. Antihypertensive effect of passion fruit peel extract and its major bioactive components following acute supplementation in spontaneously hypertensive rats. J Nutr Biochem 2013; 24:1359-66. [DOI: 10.1016/j.jnutbio.2012.11.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 10/24/2012] [Accepted: 11/02/2012] [Indexed: 12/13/2022]
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15
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Hildreth CM, Kandukuri DS, Goodchild AK, Phillips JK. Temporal development of baroreceptor dysfunction in a rodent model of chronic kidney disease. Clin Exp Pharmacol Physiol 2013; 40:458-65. [DOI: 10.1111/1440-1681.12110] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 05/01/2013] [Accepted: 05/07/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Cara M Hildreth
- Australian School of Advanced Medicine; Macquarie University; Sydney; NSW; Australia
| | - Divya Sarma Kandukuri
- Australian School of Advanced Medicine; Macquarie University; Sydney; NSW; Australia
| | - Ann K Goodchild
- Australian School of Advanced Medicine; Macquarie University; Sydney; NSW; Australia
| | - Jacqueline K Phillips
- Australian School of Advanced Medicine; Macquarie University; Sydney; NSW; Australia
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16
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Carll AP, Willis MS, Lust RM, Costa DL, Farraj AK. Merits of non-invasive rat models of left ventricular heart failure. Cardiovasc Toxicol 2012; 11:91-112. [PMID: 21279739 DOI: 10.1007/s12012-011-9103-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Heart failure (HF) is characterized as a limitation to cardiac output that prevents the heart from supplying tissues with adequate oxygen and predisposes individuals to pulmonary edema. Impaired cardiac function is secondary to either decreased contractility reducing ejection (systolic failure), diminished ventricular compliance preventing filling (diastolic failure), or both. To study HF etiology, many different techniques have been developed to elicit this condition in experimental animals, with varying degrees of success. Among rats, surgically induced HF models are the most prevalent, but they bear several shortcomings, including high mortality rates and limited recapitulation of the pathophysiology, etiology, and progression of human HF. Alternatively, a number of non-invasive HF induction methods avoid many of these pitfalls, and their merits in technical simplicity, reliability, survivability, and comparability to the pathophysiologic and pathogenic characteristics of HF are reviewed herein. In particular, this review focuses on the primary pathogenic mechanisms common to genetic strains (spontaneously hypertensive and spontaneously hypertensive heart failure), pharmacological models of toxic cardiomyopathy (doxorubicin and isoproterenol), and dietary salt models, all of which have been shown to induce left ventricular HF in the rat. Additional non-invasive techniques that may potentially enable the development of new HF models are also discussed.
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Affiliation(s)
- Alex P Carll
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, 27599 USA.
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Farraj AK, Hazari MS, Winsett DW, Kulukulualani A, Carll AP, Haykal-Coates N, Lamb CM, Lappi E, Terrell D, Cascio WE, Costa DL. Overt and latent cardiac effects of ozone inhalation in rats: evidence for autonomic modulation and increased myocardial vulnerability. ENVIRONMENTAL HEALTH PERSPECTIVES 2012; 120:348-54. [PMID: 22138703 PMCID: PMC3295357 DOI: 10.1289/ehp.1104244] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 12/02/2011] [Indexed: 05/22/2023]
Abstract
BACKGROUND Ozone (O₃) is a well-documented respiratory oxidant, but increasing epidemiological evidence points to extrapulmonary effects, including positive associations between ambient O₃ concentrations and cardiovascular morbidity and mortality. OBJECTIVE With preliminary reports linking O₃ exposure with changes in heart rate (HR), we investigated the hypothesis that a single inhalation exposure to O₃ will cause concentration-dependent autonomic modulation of cardiac function in rats. METHODS Rats implanted with telemeters to monitor HR and cardiac electrophysiology [electrocardiography (ECG)] were exposed once by whole-body inhalation for 4 hr to 0.2 or 0.8 ppm O₃ or filtered air. A separate cohort was tested for vulnerability to aconitine-induced arrhythmia 24 hr after exposure. RESULTS Exposure to 0.8 ppm O₃ caused bradycardia, PR prolongation, ST depression, and substantial increases in atrial premature beats, sinoatrial block, and atrioventricular block, accompanied by concurrent increases in several HR variability parameters that were suggestive of increased parasympathetic tone. Low-O₃ exposure failed to elicit any overt changes in autonomic tone, heart rhythm, or ECG. However, both 0.2 and 0.8 ppm O₃ increased sensitivity to aconitine-induced arrhythmia formation, suggesting a latent O₃-induced alteration in myocardial excitability. CONCLUSIONS O₃ exposure causes several alterations in cardiac electrophysiology that are likely mediated by modulation of autonomic input to the heart. Moreover, exposure to low O₃ concentrations may cause subclinical effects that manifest only when triggered by a stressor, suggesting that the adverse health effects of ambient levels of air pollutants may be insidious and potentially underestimated.
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Affiliation(s)
- Aimen K Farraj
- Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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18
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Lamb CM, Hazari MS, Haykal-Coates N, Carll AP, Krantz QT, King C, Winsett DW, Cascio WE, Costa DL, Farraj AK. Divergent electrocardiographic responses to whole and particle-free diesel exhaust inhalation in spontaneously hypertensive rats. Toxicol Sci 2011; 125:558-68. [PMID: 22052608 DOI: 10.1093/toxsci/kfr296] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Diesel exhaust (DE) is a major contributor to traffic-related fine particulate matter (PM)(2.5). Although inroads have been made in understanding the mechanisms of PM-related health effects, DE's complex mixture of PM, gases, and volatile organics makes it difficult to determine how the constituents contribute to DE's effects. We hypothesized that exposure to particle-filtered DE (fDE; gases alone) will elicit less cardiac effects than whole DE (wDE; particles plus gases). In addition, we hypothesized that spontaneously hypertensive (SH) rats will be more sensitive to the electrocardiographic effects of DE exposure than Wistar Kyoto rats (WKY; background strain with normal blood pressure). SH and WKY rats, implanted with telemeters to monitor electrocardiogram and heart rate (HR), were exposed once for 4 h to 150 μg/m(3) or 500 μg/m(3) of wDE (gases plus PM) or fDE (gases alone) DE, or filtered air. Exposure to fDE, but not wDE, caused immediate electrocardiographic alterations in cardiac repolarization (ST depression) and atrioventricular conduction block (PR prolongation) as well as bradycardia in SH rats. Exposure to wDE, but not fDE, caused postexposure ST depression and increased sensitivity to the pulmonary C fiber agonist capsaicin in SH rats. The only notable effect of DE exposure in WKY rats was a decrease in HR. Taken together, hypertension may predispose to the potential cardiac effects of DE and components of DE may have divergent effects with some eliciting immediate irritant effects (e.g., gases), whereas others (e.g., PM) trigger delayed effects potentially via separate mechanisms.
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Affiliation(s)
- Christina M Lamb
- Curriculum in Toxicology, University of North Carolina, Chapel Hill, North Carolina 27514, USA
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Tchekalarova J, Pechlivanova D, Atanasova T, Markova P, Lozanov V, Stoynev A. Diurnal variations in depression-like behavior of Wistar and spontaneously hypertensive rats in the kainate model of temporal lobe epilepsy. Epilepsy Behav 2011; 20:277-85. [PMID: 21277833 DOI: 10.1016/j.yebeh.2010.12.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 12/14/2010] [Accepted: 12/14/2010] [Indexed: 11/26/2022]
Abstract
The purpose of this study was to explore whether the kainate (KA) model of temporal lobe epilepsy (TLE) can be used as a model of comorbid epilepsy and depression to study diurnal behavioral variations in rats. Development of chronic epilepsy was confirmed by the detection of spontaneous motor seizures (SMS) with video monitoring (24 hours/3-5 months after status epilepticus [SE]). KA-treated spontaneously hypertensive rats (SHRs) exhibited higher seizure frequency than Wistar rats during the light phase in the fourth and fifth months after SE. Although epileptic Wistar rats showed depression-like behavior and reduced anxiety mostly during the light phase, there were no diurnal variations in depression-like patterns in SHRs. Anxiety levels of control and epileptic SHRs were similar. Decreases in serotonin, tryptophan, and dopamine concentrations in the hippocampus were detected in epileptic Wistar rats compared with naive controls. However, monoamine levels of epileptic SHRs were close to those of their controls. Wistar rats and SHRs develop stable depression-like behavior during the chronic epileptic phase with strain-dependent diurnal differences.
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Affiliation(s)
- Jana Tchekalarova
- Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
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20
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Beneficial cardiac effects of the renin inhibitor aliskiren in spontaneously hypertensive rats. J Hypertens 2011; 28:2145-55. [PMID: 20625318 DOI: 10.1097/hjh.0b013e32833d01ae] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND The blood pressure-lowering effect of the renin inhibitor aliskiren equals that of angiotensin-converting enzyme (ACE) inhibitors and angiotensin (Ang) II type 1 (AT1) receptor blockers. Whether aliskiren offers end-organ protection remains to be investigated. Here, we compared the cardiac effects of aliskiren, the AT1 receptor blocker irbesartan and the ACE inhibitor captopril in spontaneously hypertensive rats (SHR) at equi-hypotensive doses. METHODS AND RESULTS SHR were treated for 1-3 weeks with vehicle, aliskiren, captopril or irbesartan (100, 3 and 15 mg/kg per day, respectively) using an osmotic minipump, and compared to vehicle-treated Wistar-Kyoto (WKY) controls. All drugs lowered (but not normalized) mean arterial pressure in SHR equi-effectively, as monitored by radiotelemetry, without altering heart rate. All drugs also reduced the increased cardiomyocyte area in SHR, and tended to normalize the elevated brain natriuretic peptide plasma levels. In the Langendorff set-up, all drugs normalized the diminished endothelium-dependent vasodilator response to bradykinin in SHR. Moreover, aliskiren and irbesartan, but not captopril, decreased the enhanced coronary Ang II response in SHR. Aliskiren reduced plasma renin activity and the plasma and tissue angiotensin levels at 1 week of treatment; yet, after 3 weeks of aliskiren treatment only the cardiac angiotensin levels remained suppressed, whereas no tissue angiotensin reductions were seen with captopril or irbesartan. CONCLUSION For a given decrease in blood pressure, aliskiren improves coronary endothelial function and decreases cardiac hypertrophy in SHR to at least the same degree as ACE inhibition and AT1 receptor blockade. In addition, aliskiren diminishes the enhanced Ang II response in the coronary circulation of SHR and offers superior long-term cardiac angiotensin suppression.
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Farraj AK, Hazari MS, Haykal-Coates N, Lamb C, Winsett DW, Ge Y, Ledbetter AD, Carll AP, Bruno M, Ghio A, Costa DL. ST depression, arrhythmia, vagal dominance, and reduced cardiac micro-RNA in particulate-exposed rats. Am J Respir Cell Mol Biol 2010; 44:185-96. [PMID: 20378750 DOI: 10.1165/rcmb.2009-0456oc] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Recently, investigators demonstrated associations between fine particulate matter (PM)-associated metals and adverse health effects. Residual oil fly ash (ROFA), a waste product of fossil fuel combustion from boilers, is rich in the transition metals Fe, Ni, and V, and when released as a fugitive particle, is an important contributor to ambient fine particulate air pollution. We hypothesized that a single-inhalation exposure to transition metal-rich PM will cause concentration-dependent cardiovascular toxicity in spontaneously hypertensive (SH) rats. Rats implanted with telemeters to monitor heart rate and electrocardiogram were exposed once by nose-only inhalation for 4 hours to 3.5 mg/m(3), 1.0 mg/m(3), or 0.45 mg/m(3) of a synthetic PM (dried salt solution), similar in composition to a well-studied ROFA sample consisting of Fe, Ni, and V. Exposure to the highest concentration of PM decreased T-wave amplitude and area, caused ST depression, reduced heart rate (HR), and increased nonconducted P-wave arrhythmias. These changes were accompanied by increased pulmonary inflammation, lung resistance, and vagal tone, as indicated by changes in markers of HR variability (increased root of the mean of squared differences of adjacent RR intervals [RMSSD], low frequency [LF], high frequency [HF], and decreased LF/HF), and attenuated myocardial micro-RNA (RNA segments that suppress translation by targeting messenger RNA) expression. The low and intermediate concentrations of PM had less effect on the inflammatory, HR variability, and micro-RNA endpoints, but still caused significant reductions in HR. In addition, the intermediate concentration caused ST depression and increased QRS area, whereas the low concentration increased the T-wave parameters. Thus, PM-induced cardiac dysfunction is mediated by multiple mechanisms that may be dependent on PM concentration and myocardial vulnerability (this abstract does not reflect the policy of the United States Environmental Protection Agency).
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Affiliation(s)
- Aimen K Farraj
- Environmental Public Health Division, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
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Tchekalarova J, Pechlivanova D, Itzev D, Lazarov N, Markova P, Stoynev A. Diurnal rhythms of spontaneous recurrent seizures and behavioral alterations of Wistar and spontaneously hypertensive rats in the kainate model of epilepsy. Epilepsy Behav 2010; 17:23-32. [PMID: 20006556 DOI: 10.1016/j.yebeh.2009.11.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 11/02/2009] [Accepted: 11/03/2009] [Indexed: 10/20/2022]
Abstract
Attention deficit hyperactivity disorder (ADHD) can coexist with epilepsy. Spontaneously hypertensive rats (SHRs) are considered to model ADHD with overactivity, impulsiveness, deficient sustained attention, and alterations in circadian autonomic profiles. The present study explored spontaneous recurrent seizures (SRSs) and behavioral diurnal activity rhythms in normotensive Wistar rats and SHRs in the kainate model of epilepsy. Rats were video monitored (24 h/3 months) to detect SRSs. SHRs manifested a lower seizure frequency during the light phase in the 8th and 10th weeks and a lower frequency of SRSs during the night phase accompanied by attenuated responses in hyperexcitability tests. Both epileptic strains were hyperactive, with lower anxiety levels, and their diurnal rhythms were abolished. Epileptic Wistar rats and SHRs exhibited less exploration during the dark phase. This study suggests that SHRs may be useful in modeling some aspects (particularly hypertension-related diurnal rhythm disturbance) of behavior associated with epilepsy.
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Affiliation(s)
- Jane Tchekalarova
- Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
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Zamo FS, Lacchini S, Mostarda C, Chiavegatto S, Silva ICM, Oliveira EM, Irigoyen MC. Hemodynamic, morphometric and autonomic patterns in hypertensive rats - Renin-Angiotensin system modulation. Clinics (Sao Paulo) 2010; 65:85-92. [PMID: 20126350 PMCID: PMC2815287 DOI: 10.1590/s1807-59322010000100013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Accepted: 10/22/2009] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Spontaneously hypertensive rats develop left ventricular hypertrophy, increased blood pressure and blood pressure variability, which are important determinants of heart damage, like the activation of renin-angiotensin system. AIMS To investigate the effects of the time-course of hypertension over 1) hemodynamic and autonomic patterns (blood pressure; blood pressure variability; heart rate); 2) left ventricular hypertrophy; and 3) local and systemic Renin-angiotensin system of the spontaneously hypertensive rats. METHODS MALE SPONTANEOUSLY HYPERTENSIVE RATS WERE RANDOMIZED INTO TWO GROUPS: young (n=13) and adult (n=12). Hemodynamic signals (blood pressure, heart rate), blood pressure variability (BPV) and spectral analysis of the autonomic components of blood pressure were analyzed. LEFT ventricular hypertrophy was measured by the ratio of LV mass to body weight (mg/g), by myocyte diameter (mum) and by relative fibrosis area (RFA, %). ACE and ACE2 activities were measured by fluorometry (UF/min), and plasma renin activity (PRA) was assessed by a radioimmunoassay (ng/mL/h). Cardiac gene expressions of Agt, Ace and Ace2 were quantified by RT-PCR (AU). RESULTS The time-course of hypertension in spontaneously hypertensive rats increased BPV and reduced the alpha index in adult spontaneously hypertensive rats. Adult rats showed increases in left ventricular hypertrophy and in RFA. Compared to young spontaneously hypertensive rats, adult spontaneously hypertensive rats had lower cardiac ACE and ACE2 activities, and high levels of PRA. No change was observed in gene expression of Renin-angiotensin system components. CONCLUSIONS The observed autonomic dysfunction and modulation of Renin-angiotensin system activity are contributing factors to end-organ damage in hypertension and could be interacting. Our findings suggest that the management of hypertensive disease must start before blood pressure reaches the highest stable levels and the consequent established end-organ damage is reached.
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Affiliation(s)
- Fernanda S Zamo
- Nephrology Department, Federal University of São Paulo - São Paulo/SP, Brazil.
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Synergistic decrease in blood pressure by captopril combined with losartan in spontaneous hypertensive rats. Arch Pharm Res 2009; 32:955-62. [DOI: 10.1007/s12272-009-1619-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 06/04/2009] [Accepted: 06/08/2009] [Indexed: 10/20/2022]
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El-Mas MM, Abdel-Rahman AA. Intermittent Clonidine Regimen Abolishes Tolerance to Its Antihypertensive Effect: A Spectral Study. J Cardiovasc Pharmacol 2007; 49:174-81. [PMID: 17414230 DOI: 10.1097/fjc.0b013e3180318afb] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The development of tolerance to the antihypertensive effect of clonidine and related imidazolines is clinically recognized. Here, we employed a restricted daytime (8:30 AM until 4:30 PM) clonidine regimen to establish a model of sustained hypotension in spontaneously hypertensive rats (SHRs). Blood pressure (BP), heart rate (HR), and myocardial contractility (dP/dt(max)) were measured by radiotelemetry in pair-fed SHRs receiving liquid diets with or without clonidine (150 microg/kg per day) for 12 weeks. The cardiovascular autonomic control was assessed by power spectral analysis [fast Fourier transformations (FFT)] of hemodynamic variability. Clonidine had no effect on dP/dt(max) and significantly decreased BP and HR during the 8 hour exposure periods throughout the study duration. BP returned to control levels during overnight periods, with no signs of rebound hypertension. FFT analysis of interbeat intervals (IBI) showed pronounced decreases and increases of spectral powers in low-frequency (IBI-LF, 0.20-0.75 Hz) and high-frequency (IBI-HF, 0.75-3 Hz) bands, respectively, in clonidine-treated rats. The IBI(LF/HF) ratio was significantly reduced by clonidine, suggesting cardiac parasympathetic dominance. Clonidine also decreased the vasomotor sympathetic tone, as reflected by the reduced BP-LF spectral density. The sympathoinhibitory effect of clonidine is further confirmed by the significant reductions in urinary norepinephrine levels. Clonidine increased urine output during the 8 hour treatment period but not during the 24 hour period. Plasma and urine osmolality and electrolytes were not altered by clonidine. It is concluded that by adopting the limited-access paradigm, tolerance to the hypotensive and sympathoinhibitory actions of clonidine and, possibly, its side effects, could be minimized.
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Affiliation(s)
- Mahmoud M El-Mas
- Department of Pharmacology, School of Medicine, East Carolina University, Greenville, NC, USA
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El-Mas MM, Abdel-Rahman AA. Autonomic Modulation of Altered Diurnal Hemodynamic Profiles in Ethanol-Fed Hypertensive Rats. Alcohol Clin Exp Res 2005; 29:499-508. [PMID: 15834214 DOI: 10.1097/01.alc.0000159108.23375.b6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND A recent report from the authors' laboratory showed that circadian hemodynamic rhythms are altered in hypertension due partly to irregularities in cardiovascular autonomic control. This study investigated the long-term effects of chronic ethanol feeding (5% w/v, 12 weeks) on the circadian profiles of blood pressure (BP), heart rate (HR), and their variability in spontaneously hypertensive rats (SHRs) and age-matched Wistar-Kyoto (WKY) rats. METHODS Radiotelemetry was used for hemodynamic monitoring. The time-domain measures of the variability of BP (standard deviation of mean arterial pressure [SDMAP]) and HR (standard deviation of R-R intervals [SDRR] and root mean square of successive differences in R-R intervals [rMSSD]) were taken as indices of cardiovascular autonomic activity. RESULTS Control WKY rats displayed normal circadian rhythms (i.e., higher dark-time compared with light-time values) of BP, HR, and their variability indices during weeks 6 through 12 of the study. These circadian rhythms were abolished (BP), inverted (HR, SDMAP), or enhanced (SDRR, rMSSD) in SHRs. Ethanol feeding produced sustained hypotension during both light and dark cycles that was 3-fold greater in SHRs than in WKY rats. SDMAP was not affected by ethanol in WKY rats and showed reductions, mostly during light times, in SHRs. Ethanol also caused significant increases in HR in SHRs only during dark periods, probably because of the inhibition of cardiac vagal activity as indicated by temporal reductions in rMSSD. CONCLUSIONS These results implicate autonomic factors in the altered diurnal hemodynamic profile by ethanol in SHRs and highlight the possibility of increased risk of cardiac events in hypertensive patients due to alcohol use.
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Affiliation(s)
- Mahmoud M El-Mas
- Department of Pharmacology, School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA
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