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Cai M, Wang H, Kline G, Ding Y, Ross SE, Davis S, Mallet RT, Shi X. Habitual physical activity improves vagal cardiac modulation and carotid baroreflex function in elderly women. Exp Biol Med (Maywood) 2023; 248:991-1000. [PMID: 37092743 PMCID: PMC10525404 DOI: 10.1177/15353702231160334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 02/10/2023] [Indexed: 04/25/2023] Open
Abstract
The impact of habitual physical activity on vagal-cardiac function and baroreflex sensitivity in elderly women is poorly characterized. This study compared vagal-cardiac modulation and carotid baroreflex (CBR) function in eight physically active (67.6 ± 1.9 years; peak O2 uptake 29.1 ± 2.5 mL/min/kg) versus eight sedentary (67.3 ± 1.8 years; peak O2 uptake 18.6 ± 0.9 mL/min/kg) elderly women. Heart rate (HR) variabilities and maximal changes of HR and mean arterial pressure (MAP) elicited by 5-s pressure pulses between +40 and -80 mmHg applied to the carotid sinus were measured at rest and during carotid baroreceptor unloading effected by -15 mmHg lower-body negative pressure (LBNP). HR variability was greater in active than sedentary women in both low (0.998 ± 0.286 versus 0.255 ± 0.063 bpm2; P = 0.036) and high (0.895 ± 0.301 versus 0.156 ± 0.045 bpm2; P = 0.044) frequency domains. CBR-HR gains (bpm/mmHg) were greater (fitness factor P < 0.001) in active versus sedentary women at rest (-0.146 ± 0.014 versus -0.088 ± 0.011) and during LBNP (-0.105 ± 0.014 versus -0.065 ± 0.008). CBR-MAP gains (mmHg/mmHg) tended to be greater (fitness factor P = 0.077) in active versus sedentary women at rest (-0.132 ± 0.013 versus -0.110 ± 0.011) and during LBNP (-0.129 ± 0.015 versus -0.113 ± 0.013). However, LBNP did not potentiate CBR-MAP gains in either sedentary or active women (LBNP factor P = 0.94), and it depressed CBR-HR gains in both groups (LBNP factor P = 0.003). CBR-HR gains in the sedentary women did not differ (sex factor P = 0.65) from gains reported in age-matched sedentary men, although CBR-MAP gains tended to be greater (sex factor P = 0.109) in the men. Thus, tonic vagal modulation indicated by HR variability and dynamic vagal responses assessed by CBR-HR gain were augmented in physically active women. Enhanced vagal-cardiac function may protect against senescence-associated cardiac electrical and hemodynamic instability in elderly women.
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Affiliation(s)
- Ming Cai
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
- Shanghai University of Medicine & Health Sciences, Shanghai, 201318, China
| | - Hong Wang
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
- Shanghai University of Medicine & Health Sciences, Shanghai, 201318, China
| | - Geoffrey Kline
- Department of Internal Medicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Yanfeng Ding
- Department of Internal Medicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Sarah E Ross
- Department of Internal Medicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Sandra Davis
- Department of Internal Medicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Robert T Mallet
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107-2699, USA
| | - Xiangrong Shi
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
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Pastormerlo LE, Burchielli S, Ciardetti M, Aquaro GD, Grigoratos C, Castiglione V, Pucci A, Franzini M, Giorgetti A, Marzullo P, Benelli E, Masotti S, Musetti V, Bernini F, Berti S, Passino C, Emdin M. Myocardial salvage is increased after sympathetic renal denervation in a pig model of acute infarction. Clin Res Cardiol 2020; 110:711-724. [PMID: 32514602 DOI: 10.1007/s00392-020-01685-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 06/02/2020] [Indexed: 12/16/2022]
Abstract
RATIONALE Despite advances in treatment of acute myocardial infarction (AMI), many patients suffer significant myocardial damage with cardiac dysfunction. Sympathetic renal denervation (RD) may reduce adrenergic activation following AMI. OBJECTIVE To investigate the potential role of RD limiting myocardial damage and remodeling when performed immediately after AMI. METHODS AND RESULTS Sixteen farm pigs underwent 90 min left anterior descending artery balloon occlusion. Eight pigs underwent RD immediately after reperfusion. LV function, extent of myocardium at risk, and myocardial necrosis were quantified by cardiac magnetic resonance 5 and 30 days after AMI. 123I-MIBG scintigraphy was performed 31 days after AMI to image myocardial sympathetic innervation. Heart norepinephrine was quantified (from necrotic, border and remote zone). RD and control did not differ in myocardium at risk extent (59 ± 9 vs 55 ± 11% of LV mass) at 5 days. At 30 days CMR, RD pigs had smaller necrotic areas than control as assessed by gadolinium delay enhancement (18 ± 7 vs 30 ± 12% of LV mass, p = 0.021) resulting in improved myocardial salvage index (60 ± 11 vs 44 ± 27%, p < 0.001). RD pigs had higher cardiac output (3.7 ± 0.8 vs 2.66 ± 0.7 L/min, p < 0.001) and lower LV end diastolic volume (98 ± 16 vs 113 ± 31 ml, p = 0.041). 123I-MIBG defect extension was smaller in RD than control (60 ± 28 vs 78 ± 17%, p < 0.05) with significant reduction in the difference between innervation and perfusion defects (25 ± 12 vs 36 ± 30%, p = 0.013). NE content from necrotic area (238; IQR 464 vs 2546; IQR 1727 ng/g in RD and control, respectively, p < 0.001) and from border zone (295; IQR 264 vs 837; IQR 207 in RD and control, respectively, p = 0.031) was significantly lower in RD than control. CONCLUSIONS RD results in increased myocardial salvage and better cardiac function, when performed immediately after AMI. Reduction of sympathetic activation with preservation of cardiac sympathetic functionality warranted by RD may sustain these effects.
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Affiliation(s)
- Luigi Emilio Pastormerlo
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy. .,Life Sciences Institute, Scuola Superiore Sant'Anna, Pisa, Italy. .,Division of Cardiovascular Medicine, Fondazione Toscana Gabriele Monasterio CNR-Regione Toscana, Via Giuseppe Moruzzi 1, 56124, Pisa, Italy.
| | | | - Marco Ciardetti
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy
| | | | - Chrysantos Grigoratos
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy.,Life Sciences Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | | | - Angela Pucci
- Institute of Clinical Pathology, University of Pisa, Pisa, Italy
| | - Maria Franzini
- Institute of Clinical Pathology, University of Pisa, Pisa, Italy
| | | | - Paolo Marzullo
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy
| | - Eleonora Benelli
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy
| | - Silvia Masotti
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy
| | - Veronica Musetti
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy
| | - Fabio Bernini
- Life Sciences Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Sergio Berti
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy
| | - Claudio Passino
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy.,Life Sciences Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Michele Emdin
- Fondazione G. Monasterio CNR-Regione Toscana, Massa, Pisa, Italy.,Life Sciences Institute, Scuola Superiore Sant'Anna, Pisa, Italy
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Blomster H, Laitinen TP, Hartikainen JE, Laitinen TM, Vanninen E, Gylling H, Sahlman J, Kokkarinen J, Randell J, Seppä J, Tuomilehto H. Mild obstructive sleep apnea does not modulate baroreflex sensitivity in adult patients. Nat Sci Sleep 2015. [PMID: 26203292 PMCID: PMC4487157 DOI: 10.2147/nss.s82443] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Obstructive sleep apnea (OSA) is a chronic and progressive disease. OSA is associated with increased cardiovascular morbidity and mortality, the risk being more frequently encountered with severe degrees of OSA. Increased sympathetic activation and impaired cardiac autonomic control as reflected by depressed baroreceptor reflex sensitivity (BRS) are possible mechanisms involved in the cardiovascular complications of OSA. However, it is not known at what stage of OSA that changes in BRS appear. The aim of this study was to evaluate BRS in patients with mild OSA. METHODS The study population consisted of 81 overweight patients with mild OSA and 46 body weight-matched non-OSA subjects. BRS, apnea-hypopnea index, body mass index, and metabolic parameters were assessed. The phenylephrine test was used to measure BRS. RESULTS Patients in the OSA group were slightly but significantly older than the non-OSA population (50.3±9.3 years vs 45.7±11.1 years, P=0.02). Body mass index, percentage body fat, blood pressure, fasting glucose, insulin, and lipid levels did not differ between the OSA patients and non-OSA subjects. Absolute BRS values in patients with mild OSA and non-OSA subjects (9.97±6.70 ms/mmHg vs 10.51±7.16 ms/mmHg, P=0.67) and BRS values proportional to age-related and sex-related reference values (91.4%±22.7% vs 92.2%±21.8%, P=0.84) did not differ from each other. BRS <50% of the sex-specific reference value was found in 6% of patients with mild OSA and in 2% of non-OSA subjects (P=0.29). CONCLUSION Patients with mild OSA did not show evidence of disturbed BRS in comparison with weight-matched non-OSA controls.
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Affiliation(s)
- Henry Blomster
- Department of Otorhinolaryngology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Tomi P Laitinen
- Department of Clinical Physiology and Nuclear Medicine, University of Eastern Finland, Kuopio, Finland
| | - Juha Ek Hartikainen
- Department of Internal Medicine, University of Eastern Finland, Kuopio, Finland ; Heart Center, Kuopio University Hospital, Kuopio, Finland
| | - Tiina M Laitinen
- Department of Clinical Physiology and Nuclear Medicine, University of Eastern Finland, Kuopio, Finland
| | - Esko Vanninen
- Department of Clinical Physiology and Nuclear Medicine, University of Eastern Finland, Kuopio, Finland
| | - Helena Gylling
- Department of Clinical Nutrition, School of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland ; Department of Medicine, Division of Internal Medicine, University of Helsinki, Helsinki, Finland
| | - Johanna Sahlman
- Department of Otorhinolaryngology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Jouko Kokkarinen
- Department of Respiratory Medicine, Kuopio University Hospital, Kuopio, Finland
| | - Jukka Randell
- Department of Respiratory Medicine, Kuopio University Hospital, Kuopio, Finland
| | - Juha Seppä
- Department of Otorhinolaryngology, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland
| | - Henri Tuomilehto
- Department of Clinical Nutrition, School of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland ; Oivauni Sleep Clinic, Kuopio, Finland
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Spary EJ, Maqbool A, Batten TFC. Changes in oestrogen receptor alpha expression in the nucleus of the solitary tract of the rat over the oestrous cycle and following ovariectomy. J Neuroendocrinol 2010; 22:492-502. [PMID: 20236229 DOI: 10.1111/j.1365-2826.2010.01977.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Oestrogen is capable of modulating autonomic outflow and baroreflex function via actions on groups of neurones in the brainstem. We investigated the presence of oestrogen receptor (ER) alpha in a part of the nucleus of the solitary tract (NTS) associated with central cardiovascular control, aiming to determine whether ERalpha mRNA and protein expression is correlated with levels of circulating oestrogen during the oestrous cycle. Polymerase chain reaction (PCR) detected ERalpha mRNA in the NTS at each stage of the oestrous cycle, from ovariectomised, sham-operated and male rats. Real-time PCR showed variations in ERalpha mRNA expression during the oestrous cycle, with the highest levels seen in oestrus, and lowest levels in metoestrus (P < 0.05 versus oestrus) and proestrus (P < 0.05 versus oestrus). Expression in males was lower than in dioestrus and oestrus females (P < 0.05). After ovariectomy, ERalpha mRNA levels were decreased compared to sham-operated animals (P < 0.01). Confocal fluorescence immunohistochemistry with stereological analysis showed that numbers of ERalpha immunoreactive cell nuclei per mm(3) of tissue in the caudal NTS were significantly greater in proestrus than in other groups of rats (P < 0.05). There were also differences among the groups in the extent of colocalisation of ERalpha in neurones immunoreactive for tyrosine hydroxylase and nitric oxide synthase. These results imply a complex pattern of region-specific oestrogen signalling in the NTS and suggest that ERalpha expression in this important autonomic nucleus may be related to circulating oestrogen levels. This may have consequences for the regulation of autonomic tone and baroreflex sensitivity when oestrogen levels decline, for example following menopause.
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Affiliation(s)
- E J Spary
- Division of Cardiovascular and Neuronal Remodelling, LIGHT Institute, University of Leeds, Leeds, UK.
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Niskanen L, Laitinen T, Tuppurainen M, Saarikoski S, Kröger H, Alhava E, Hartikainen J. Does postmenopausal hormone replacement therapy affect cardiac autonomic regulation in osteoporotic women? Menopause 2002; 9:52-7. [PMID: 11791086 DOI: 10.1097/00042192-200201000-00008] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Postmenopausal hormone replacement therapy (HRT) has been associated with reduced risk of cardiovascular disease; however, the mechanisms remain obscure, and it is not known whether this applies to regimens containing both estrogen and progestin. One possibility is that estrogen would act via enhancement of cardiac autonomic regulation. DESIGN In this prospective, controlled study of 6-months duration, 22 osteoporotic, postmenopausal women in the intervention group were treated with combined estradiol hemihydrate corresponding to estradiol 2 mg and norethisterone acetate 1 mg with or without clodronate (HRT group). Nine women in the control group received clodronate only. Indices of heart rate variability (HRV) by power spectral analyses and baroreceptor sensitivity (BRS) by phenylephrine test were measured before and after 3 and 6 months of treatment. RESULTS The total power of HRV remained identical within the groups, although it was higher at 3 and 6-month measurements in the control group than the HRT group. This was mainly due to lower very low frequency and high frequency power in the HRT group. However, no changes in the low frequency/high frequency-ratio of HRV, an index of sympathovagal balance, were observed between and within the groups. Further, during the intervention, no significant changes in BRS (baseline and 6 months: 5.0 +/- 2.1 and 5.1 +/- 2.5 ms/mmHg) within the HRT group was observed. CONCLUSIONS The impact of estrogen and progesterone on cardiac autonomic regulation seems to be quite modest. Therefore, cardiac morbidity and mortality are probably not mediated by their effects on cardiac autonomic regulation. However, the effects of estrogen alone or more selective estrogen receptor modulators need yet to be clarified in future studies.
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Affiliation(s)
- Leo Niskanen
- Department of Medicine, Building Number 5, Kuopio University Hospital, PO Box 1777, FIN-70211 Kuopio, Finland.
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Weston PJ, Gill GV. Is undetected autonomic dysfunction responsible for sudden death in Type 1 diabetes mellitus? The 'dead in bed' syndrome revisited. Diabet Med 1999; 16:626-31. [PMID: 10477206 DOI: 10.1046/j.1464-5491.1999.00121.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS Sudden nocturnal death in young persons with Type 1 diabetes mellitus has been recently described, and is known as the 'dead in bed' syndrome. Its aetiology is unknown, and we have therefore explored the details of all papers recording the syndrome, to formulate a hypothesis of causation. METHODS Literature review of 'dead in bed' reports as well as of nocturnal hypoglycaemia, and autonomic dysfunction in relation to baroreceptor-cardiac reflex sensitivity. RESULTS Clinical reports of 'dead in bed' cases strongly suggest that nocturnal hypoglycaemia is a likely precipitant, but that the death is sudden and probably arrhythmic. Ventricular dysrhythmias may occur in the context of early autonomic neuropathy, with relative sympathetic overactivity, in young Type 1 diabetic persons. CONCLUSION We conclude that the 'dead in bed' syndrome probably occurs in Type 1 diabetic persons with early autonomic neuropathy, resulting in relative sympathetic overactivity. In such persons, risks of ventricular dysrhythmias will be compounded by nocturnal hypoglycaemia, which may be associated with an increase in the electrocardiographic Q-T interval, and Q-T dispersion. This could lead to the observed sudden death in undisturbed beds. Further research in this area is urgently needed, in particular into the possible protective use of drugs that modulate the autonomic nervous system.
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Affiliation(s)
- P J Weston
- Diabetes Research Unit, University Hospital Aintree, Liverpool, UK
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Harris ND, Heller SR. Sudden death in young patients with Type 1 diabetes: a consequence of disease, treatment or both? Diabet Med 1999; 16:623-5. [PMID: 10477205 DOI: 10.1046/j.1464-5491.1999.00046.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Saleh TM, Connell BJ, Allen GV. Visceral afferent activation-induced changes in sympathetic nerve activity and baroreflex sensitivity. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:R1780-91. [PMID: 10362760 DOI: 10.1152/ajpregu.1999.276.6.r1780] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The following experiments were done to determine whether changes in baroreflex sensitivity evoked by cervical vagus nerve stimulation are due to sympathoexcitation mediated by the parabrachial nucleus. The relative contribution of cardiopulmonary and general gastric afferents within the cervical vagus nerve to the depression in baroreflex sensitivity are also investigated. Male Sprague-Dawley rats anesthetized with thiobutabarbital sodium (50 mg/kg) were instrumented to measure blood pressure and heart rate or for the continuous monitoring of renal sympathetic nerve activity. Baroreflex sensitivity was measured using bolus injections of phenylephrine. Electrical stimulation of the cervical vagus (with or without the aortic depressor nerve) or the abdominal vagus nerve produced a significant increase in renal nerve activity and a decrease in baroreflex sensitivity. Both of these effects were blocked after the microinjection of lidocaine into the parabrachial nucleus before nerve stimulation. Therefore, we conclude that an increase in the activity of cardiac, pulmonary, or general gastric afferents mediated the increased sympathetic output and decreased baroreflex sensitivity via a pathway involving the parabrachial nucleus.
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Affiliation(s)
- T M Saleh
- Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island C1A 4P3, Nova Scotia, Canada B3H 4H7.
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Saleh TM, Connell BJ. Centrally mediated effect of 17beta-estradiol on parasympathetic tone in male rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:R474-81. [PMID: 9950927 DOI: 10.1152/ajpregu.1999.276.2.r474] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The following experiments were conducted to determine if peripherally administered estrogen has an effect on central autonomic tone and whether this change in tone results in an alteration in cardiovascular reflex control. Male Sprague-Dawley rats were anesthetized with thiobutabarbitol sodium (50 mg/kg) and instrumented to record blood pressure, heart rate, and vagal parasympathetic or renal sympathetic efferent nerve activity. Additional rats were instrumented to test the sensitivity of the cardiac baroreflex using intravenous injections of phenylephrine hydrochloride (0.025, 0.05, 0.1 mg/kg) or sodium nitroprusside (0. 0025, 0.005, 0.01 mg/kg) and plotting the cardiovascular responses. Intravenous injection of estrogen (10(-4), 10(-2), and 10(-1) mg/kg) produced a significant increase in vagal efferent activity and in baroreflex sensitivity. The bilateral microinjection of an estrogen receptor antagonist, ICI-182,780 (1 pM, 50 nl/side) into the nucleus ambiguus blocked both the estrogen-induced increase in vagal efferent activity and baroreflex sensitivity. These results demonstrate that in male rats estrogen acts centrally to enhance baroreflex sensitivity by increasing parasympathetic efferent tone.
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Affiliation(s)
- T M Saleh
- Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3
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Saleh TM, Connell BJ. Role of 17beta-estradiol in the modulation of baroreflex sensitivity in male rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:R770-8. [PMID: 9728074 DOI: 10.1152/ajpregu.1998.275.3.r770] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Female mammals have an enhanced baroreflex sensitivity compared with their male counterparts, leading researchers to speculate that estrogen modulates autonomic tone. Therefore, this study tests the hypothesis that exogenous estrogen can enhance the baroreflex sensitivity of male rats. Male Sprague-Dawley rats anesthetized with thiobutabarbitol sodium (50 mg/kg) were instrumented to measure blood pressure and heart rate and for the intravenous injection of drugs. The baroreflex was tested using intravenous injections of phenylephrine (0.025, 0.05, and 0.1 mg/kg), and the cardiovascular responses were plotted to obtain a measure of the sensitivity of the cardiac baroreflex. Intravenous injection of estrogen produced dose-related increases in the baroreflex sensitivity due to an increase in the magnitude of the reflex bradycardia. In a separate group of animals, stimulation of the vagus nerve for 2 h resulted in a decrease in baroreflex sensitivity. This effect was blocked when estrogen (1 x 10(-2) mg/kg) was administered immediately before the end of stimulation. In conclusion, intravenous injection of estrogen in male rats significantly enhanced baroreflex sensitivity and blocked the attenuation in the baroreflex sensitivity observed after vagal stimulation.
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Affiliation(s)
- T M Saleh
- Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3
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Saleh TM, Connell BJ. Role of the insular cortex in the modulation of baroreflex sensitivity. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:R1417-24. [PMID: 9612410 DOI: 10.1152/ajpregu.1998.274.5.r1417] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cervical vagal stimulation for 2 h results in a depressed baroreflex sensitivity produced by an enhanced sympathetic output, as indicated by increased plasma norepinephrine levels. The current study examined the role of the insular cortex in modulating the vagal stimulation-induced changes in baroreflex sensitivity. Male Sprague-Dawley rats were anesthetized with thiobutabarbitol sodium and instrumented for recording blood pressure, heart rate, intravenous drug administration, and vagal afferent nerve stimulation. Stereotaxic microinjections (300 nl) of either 5% lidocaine or 0.9% saline were made bilaterally into the insula. Thirty minutes after 2 h of vagal stimulation, the baroreflex was significantly depressed and plasma norepinephrine levels were significantly elevated in both groups. The baroreflex was also significantly depressed after bilateral lidocaine injections into the insula, independent of vagal stimulation. However, no significant change in plasma norepinephrine was observed, suggesting that an attenuated parasympathetic output contributed to the altered baroreflex. Taken together, the results suggest that the insular cortex modulates the cardiac baroreflex through a modulation of parasympathetic output.
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Affiliation(s)
- T M Saleh
- Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Canada
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Laitinen T, Hartikainen J, Vanninen E, Niskanen L, Geelen G, Länsimies E. Age and gender dependency of baroreflex sensitivity in healthy subjects. J Appl Physiol (1985) 1998; 84:576-83. [PMID: 9475868 DOI: 10.1152/jappl.1998.84.2.576] [Citation(s) in RCA: 193] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We evaluated the correlates of baroreflex sensitivity (BRS) in healthy subjects. The study consisted of 117 healthy, normal-weight, nonsmoking male and female subjects aged 23-77 yr. Baroreflex control of heart rate was measured by using the phenylephrine bolus-injection technique. Frequency- and time-domain analysis of heart rate variability and an exercise test were performed. Plasma norepinephrine, epinephrine, insulin, and arginine vasopressin concentrations and plasma renin activity were measured. In the univariate analysis, BRS correlated with age (r = -0.65, P < 0.001), diastolic blood pressure (r = -0.47, P < 0.001), exercise capacity (r = 0.60, P < 0.001), and the high-frequency component of heart rate variability (r = 0.64, P < 0.001). There was also a significant correlation between BRS and plasma norepinephrine concentration (r = -0.22, P < 0.05) and plasma renin activity (r = 0.32, P < 0.001). According to the multivariate analysis, age and gender were the most important physiological correlates of BRS. They accounted for 52% of interindividual BRS variation. In addition, diastolic blood pressure and high-frequency component of heart rate variability were significant independent correlates of BRS. BRS was significantly higher in men than in women (15.0 +/- 1.2 vs. 10.2 +/- 1.1 ms/mmHg, respectively; P < 0.01). Twenty-four percent of women > 40 yr old and 18% of men > 60 yr old had markedly depressed BRS (< 3 ms/mmHg). We conclude that physiological factors, particularly age and gender, have significant impact on BRS in healthy subjects. In addition, we demonstrate that BRS values that have been proposed to be useful in identifying postinfarction patients at high risk of sudden death are frequently found in healthy subjects.
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Affiliation(s)
- T Laitinen
- Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Finland.
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