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Rasmi Y, Shokati A, Hatamkhani S, Farnamian Y, Naderi R, Jalali L. Assessment of the relationship between the dopaminergic pathway and severe acute respiratory syndrome coronavirus 2 infection, with related neuropathological features, and potential therapeutic approaches in COVID-19 infection. Rev Med Virol 2024; 34:e2506. [PMID: 38282395 DOI: 10.1002/rmv.2506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 07/06/2023] [Accepted: 12/17/2023] [Indexed: 01/30/2024]
Abstract
Dopamine is a known catecholamine neurotransmitter involved in several physiological processes, including motor control, motivation, reward, cognition, and immune function. Dopamine receptors are widely distributed throughout the nervous system and in immune cells. Several viruses, including human immunodeficiency virus and Japanese encephalitis virus, can use dopaminergic receptors to replicate in the nervous system and are involved in viral neuropathogenesis. In addition, studies suggest that dopaminergic receptors may play a role in the progression and pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. When SARS-CoV-2 binds to angiotensin-converting enzyme 2 receptors on the surface of neuronal cells, the spike protein of the virus can bind to dopaminergic receptors on neighbouring cells to accelerate its life cycle and exacerbate neurological symptoms. In addition, recent research has shown that dopamine is an important regulator of the immune-neuroendocrine system. Most immune cells express dopamine receptors and other dopamine-related proteins, indicating the importance of dopaminergic immune regulation. The increase in dopamine concentration during SARS-CoV2 infection may reduce immunity (innate and adaptive) that promotes viral spread, which could lead to neuronal damage. In addition, dopaminergic signalling in the nervous system may be affected by SARS-CoV-2 infection. COVID -19 can cause various neurological symptoms as it interacts with the immune system. One possible treatment strategy for COVID -19 patients could be the use of dopamine antagonists. To fully understand how to protect the neurological system and immune cells from the virus, we need to study the pathophysiology of the dopamine system in SARS-CoV-2 infection.
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Affiliation(s)
- Yousef Rasmi
- Cellular and Molecular Research Center, Cellular and Molecular Medicine Research Institute, Urmia University of Medical Sciences, Urmia, Iran
- Department of Biochemistry, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran
| | - Ameneh Shokati
- Department of Applied Cell Sciences, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran
- Multiple Sclerosis Research Center, Neuroscience Institute, Tehran University of Medical Sciences (TUMS), Tehran, Iran
| | - Shima Hatamkhani
- Experimental and Applied Pharmaceutical Sciences Research Center, Urmia University of Medical Sciences, Urmia, Iran
- Department of Clinical Pharmacy, School of Pharmacy, Urmia University of Medical Sciences, Urmia, Iran
| | - Yeganeh Farnamian
- Student Research Committee, Urmia University of Medical Sciences, Urmia, Iran
| | - Roya Naderi
- Nephrology and Kidney Transplant Research Center, Clinical Research Institute, Urmia University of Medical Sciences, Urmia, Iran
- Department of Physiology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran
| | - Ladan Jalali
- Cellular and Molecular Research Center, Cellular and Molecular Medicine Research Institute, Urmia University of Medical Sciences, Urmia, Iran
- Department of Biochemistry, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran
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2
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A Methodological Perspective on the Function and Assessment of Peripheral Chemoreceptors in Heart Failure: A Review of Data from Clinical Trials. Biomolecules 2022; 12:biom12121758. [PMID: 36551186 PMCID: PMC9775522 DOI: 10.3390/biom12121758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/22/2022] [Accepted: 11/24/2022] [Indexed: 11/29/2022] Open
Abstract
Augmented peripheral chemoreceptor sensitivity (PChS) is a common feature of many sympathetically mediated diseases, among others, and it is an important mechanism of the pathophysiology of heart failure (HF). It is related not only to the greater severity of symptoms, especially to dyspnea and lower exercise tolerance but also to a greater prevalence of complications and poor prognosis. The causes, mechanisms, and impact of the enhanced activity of peripheral chemoreceptors (PChR) in the HF population are subject to intense research. Several methodologies have been established and utilized to assess the PChR function. Each of them presents certain advantages and limitations. Furthermore, numerous factors could influence and modulate the response from PChR in studied subjects. Nevertheless, even with the impressive number of studies conducted in this field, there are still some gaps in knowledge that require further research. We performed a review of all clinical trials in HF human patients, in which the function of PChR was evaluated. This review provides an extensive synthesis of studies evaluating PChR function in the HF human population, including methods used, factors potentially influencing the results, and predictors of increased PChS.
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Kulej-Lyko K, Niewinski P, Tubek S, Krawczyk M, Kosmala W, Ponikowski P. Inhibition of peripheral chemoreceptors improves ventilatory efficiency during exercise in heart failure with preserved ejection fraction − a role of tonic activity and acute reflex response. Front Physiol 2022; 13:911636. [PMID: 36111161 PMCID: PMC9470150 DOI: 10.3389/fphys.2022.911636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 07/19/2022] [Indexed: 11/22/2022] Open
Abstract
Peripheral chemoreceptors (PChRs) play a significant role in maintaining adequate oxygenation in the bloodstream. PChRs functionality comprises two components: tonic activity (PChT) which regulates ventilation during normoxia and acute reflex response (peripheral chemosensitivity, PChS), which increases ventilation following a specific stimulus. There is a clear link between augmented PChS and exercise intolerance in patients with heart failure with reduced ejection fraction. It has been also shown that inhibition of PChRs leads to the improvement in exercise capacity. However, it has not been established yet: 1) whether similar mechanisms take part in heart failure with preserved ejection fraction (HFpEF) and 2) which component of PChRs functionality (PChT vs. PChS) is responsible for the benefit seen after the acute experimental blockade. To answer those questions we enrolled 12 stable patients with HFpEF. All participants underwent an assessment of PChT (attenuation of minute ventilation in response to low-dose dopamine infusion), PChS (enhancement of minute ventilation in response to hypoxia) and a symptom-limited cardiopulmonary exercise test on cycle ergometer. All tests were placebo-controlled, double-blinded and performed in a randomized order. Under resting conditions and at normoxia dopamine attenuated minute ventilation and systemic vascular resistance (p = 0.03 for both). These changes were not seen with placebo. Dopamine also decreased ventilatory and mean arterial pressure responses to hypoxia (p < 0.05 for both). Inhibition of PChRs led to a decrease in V˙E/V˙CO2 comparing to placebo (36 ± 3.6 vs. 34.3 ± 3.7, p = 0.04), with no effect on peak oxygen consumption. We found a significant relationship between PChT and the relative decrement of V˙E/V˙CO2 on dopamine comparing to placebo (R = 0.76, p = 0.005). There was a trend for correlation between PChS (on placebo) and V˙E/V˙CO2 during placebo infusion (R = 0.56, p = 0.059), but the relative improvement in V˙E/V˙CO2 was not related to the change in PChS (dopamine vs. placebo). We did not find a significant relationship between PChT and PChS. In conclusion, inhibition of PChRs in HFpEF population improves ventilatory efficiency during exercise. Increased PChS is associated with worse (higher) V˙E/V˙CO2, whereas PChT predicts an improvement in V˙E/V˙CO2 after PChRs inhibition. This results may be meaningful for patient selection in further clinical trials involving PChRs modulation.
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Affiliation(s)
- Katarzyna Kulej-Lyko
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Department of Cardiology, University Clinical Hospital, Wroclaw, Poland
- *Correspondence: Katarzyna Kulej-Lyko,
| | - Piotr Niewinski
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Department of Cardiology, University Clinical Hospital, Wroclaw, Poland
| | - Stanislaw Tubek
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Department of Cardiology, University Clinical Hospital, Wroclaw, Poland
| | | | - Wojciech Kosmala
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Department of Cardiology, University Clinical Hospital, Wroclaw, Poland
| | - Piotr Ponikowski
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Department of Cardiology, University Clinical Hospital, Wroclaw, Poland
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4
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Gibbons TD, Dempsey JA, Thomas KN, Campbell HA, Stothers TAM, Wilson LC, Ainslie PN, Cotter JD. Contribution of the carotid body to thermally mediated hyperventilation in humans. J Physiol 2022; 600:3603-3624. [PMID: 35731687 DOI: 10.1113/jp282918] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 06/15/2022] [Indexed: 01/05/2023] Open
Abstract
Humans hyperventilate under heat and cold strain. This hyperventilatory response has detrimental consequences including acid-base dysregulation, dyspnoea, decreased cerebral blood flow and accelerated brain heating. The ventilatory response to hypoxia is exaggerated under whole-body heating and cooling, indicating that altered carotid body function might contribute to thermally mediated hyperventilation. To address whether the carotid body might contribute to heat- and cold-induced hyperventilation, we indirectly measured carotid body tonic activity via hyperoxia, and carotid body sensitivity via hypoxia, under graded heat and cold strain in 13 healthy participants in a repeated-measures design. We hypothesised that carotid body tonic activity and sensitivity would be elevated in a dose-dependent manner under graded heat and cold strain, thereby supporting its role in driving thermally mediated hyperventilation. Carotid body tonic activity was increased in a dose-dependent manner with heating, reaching 175% above baseline (P < 0.0005), and carotid body suppression with hyperoxia removed all of the heat-induced increase in ventilation (P = 0.9297). Core cooling increased carotid body activity by up to 250% (P < 0.0001), but maximal values were reached with mild cooling and thereafter plateaued. Carotid body sensitivity to hypoxia was profoundly increased by up to 180% with heat stress (P = 0.0097), whereas cooling had no detectable effect on hypoxic sensitivity. In summary, cold stress increased carotid body tonic activity and this effect was saturated with mild cooling, whereas heating had clear dose-dependent effects on carotid body tonic activity and sensitivity. These dose-dependent effects with heat strain indicate that the carotid body probably plays a primary role in driving heat-induced hyperventilation. KEY POINTS: Humans over-breathe (hyperventilate) when under heat and cold stress, and though this has detrimental physiological repercussions, the mechanisms underlying this response are unknown. The carotid body, a small organ that is responsible for driving hyperventilation in hypoxia, was assessed under incremental heat and cold strain. The carotid body drive to breathe, as indirectly assessed by transient hyperoxia, increased in a dose-dependent manner with heating, reaching 175% above baseline; cold stress similarly increased the carotid body drive to breathe, but did not show dose-dependency. Carotid body sensitivity, as indirectly assessed by hypoxic ventilatory responses, was profoundly increased by 70-180% with mild and severe heat strain, whereas cooling had no detectable effect. Carotid body hyperactivity and hypersensitivity are two interrelated mechanisms that probably underlie the increased drive to breathe with heat strain, whereas carotid body hyperactivity during mild cooling may play a subsidiary role in cold-induced hyperventilation.
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Affiliation(s)
- Travis D Gibbons
- School of Physical Education, Sport & Exercise Science, University of Otago, Dunedin, Otago, New Zealand.,Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Jerome A Dempsey
- John Rankin Laboratory for Pulmonary Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - Kate N Thomas
- Department of Surgical Sciences, University of Otago, Dunedin, Otago, New Zealand
| | - Holly A Campbell
- Department of Surgical Sciences, University of Otago, Dunedin, Otago, New Zealand
| | - Tiarna A M Stothers
- School of Physical Education, Sport & Exercise Science, University of Otago, Dunedin, Otago, New Zealand
| | - Luke C Wilson
- Department of Medicine, University of Otago, Dunedin, Otago, New Zealand
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - James D Cotter
- School of Physical Education, Sport & Exercise Science, University of Otago, Dunedin, Otago, New Zealand
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5
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Langner-Hetmańczuk A, Tubek S, Niewiński P, Ponikowski P. The Role of Pharmacological Treatment in the Chemoreflex Modulation. Front Physiol 2022; 13:912616. [PMID: 35774285 PMCID: PMC9237514 DOI: 10.3389/fphys.2022.912616] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 05/19/2022] [Indexed: 12/20/2022] Open
Abstract
From a physiological point of view, peripheral chemoreceptors (PCh) are the main sensors of hypoxia in mammals and are responsible for adaptation to hypoxic conditions. Their stimulation causes hyperventilation—to increase oxygen uptake and increases sympathetic output in order to counteract hypoxia-induced vasodilatation and redistribute the oxygenated blood to critical organs. While this reaction promotes survival in acute settings it may be devastating when long-lasting. The permanent overfunctionality of PCh is one of the etiologic factors and is responsible for the progression of sympathetically-mediated diseases. Thus, the deactivation of PCh has been proposed as a treatment method for these disorders. We review here physiological background and current knowledge regarding the influence of widely prescribed medications on PCh acute and tonic activities.
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Affiliation(s)
- Anna Langner-Hetmańczuk
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Institute of Heart Diseases, University Hospital, Wroclaw, Poland
| | - Stanisław Tubek
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Institute of Heart Diseases, University Hospital, Wroclaw, Poland
- *Correspondence: Stanisław Tubek,
| | - Piotr Niewiński
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Institute of Heart Diseases, University Hospital, Wroclaw, Poland
| | - Piotr Ponikowski
- Institute of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland
- Institute of Heart Diseases, University Hospital, Wroclaw, Poland
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6
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Limberg JK, Soares RN, Padilla J. Role of the Autonomic Nervous System in the Hemodynamic Response to Hyperinsulinemia-Implications for Obesity and Insulin Resistance. Curr Diab Rep 2022; 22:169-175. [PMID: 35247145 PMCID: PMC9012695 DOI: 10.1007/s11892-022-01456-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/30/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE OF REVIEW Herein, we summarize recent advances which provide new insights into the role of the autonomic nervous system in the control of blood flow and blood pressure during hyperinsulinemia. We also highlight remaining gaps in knowledge as it pertains to the translation of findings to relevant human chronic conditions such as obesity, insulin resistance, and type 2 diabetes. RECENT FINDINGS Our findings in insulin-sensitive adults show that increases in muscle sympathetic nerve activity with hyperinsulinemia do not result in greater sympathetically mediated vasoconstriction in the peripheral circulation. Both an attenuation of α-adrenergic-receptor vasoconstriction and augmented β-adrenergic vasodilation in the setting of high insulin likely explain these findings. In the absence of an increase in sympathetically mediated restraint of peripheral vasodilation during hyperinsulinemia, blood pressure is supported by increases in cardiac output in insulin-sensitive individuals. We highlight a dynamic interplay between central and peripheral mechanisms during hyperinsulinemia to increase sympathetic nervous system activity and maintain blood pressure in insulin-sensitive adults. Whether these results translate to the insulin-resistant condition and implications for long-term cardiovascular regulation warrants further exploration.
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Affiliation(s)
- Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri, 204 Gwynn Hall, Columbia, MO, 65211, USA.
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA.
| | - Rogerio N Soares
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Jaume Padilla
- Department of Nutrition and Exercise Physiology, University of Missouri, 204 Gwynn Hall, Columbia, MO, 65211, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
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7
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Hess HW, Hostler D, Clemency BM, St James E, Johnson BD. Carotid body chemosensitivity is not attenuated during cold water diving. Am J Physiol Regul Integr Comp Physiol 2021; 321:R197-R207. [PMID: 34133244 DOI: 10.1152/ajpregu.00202.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tonic carotid body (CB) activity is reduced during exposure to cold and hyperoxia. We tested the hypotheses that cold water diving lowers CB chemosensitivity and augments CO2 retention more than thermoneutral diving. Thirteen subjects [age: 26 ± 4 yr; body mass index (BMI): 26 ± 2 kg/m2) completed two 4-h head-out water immersion protocols in a hyperbaric chamber (1.6 ATA) in cold (15°C) and thermoneutral (25°C) water. CB chemosensitivity was assessed with brief hypercapnic ventilatory response ([Formula: see text]) and hypoxic ventilatory response ([Formula: see text]) tests before dive, 80 and 160 min into the dive (D80 and D160, respectively), and immediately after and 60 min after dive. Data are reported as an absolute mean (SD) change from predive. End-tidal CO2 pressure increased during both the thermoneutral water dive [D160: +2 (3) mmHg; P = 0.02] and the cold water dive [D160: +1 (2) mmHg; P = 0.03]. Ventilation increased during the cold water dive [D80: 4.13 (4.38) and D160: 7.75 (5.23) L·min-1; both P < 0.01] and was greater than the thermoneutral water dive at both time points (both P < 0.01). [Formula: see text] was unchanged during the dive (P = 0.24) and was not different between conditions (P = 0.23). [Formula: see text] decreased during the thermoneutral water dive [D80: -3.45 (3.61) and D160: -2.76 (4.04) L·min·mmHg-1; P < 0.01 and P = 0.03, respectively] but not the cold water dive. However, [Formula: see text] was not different between conditions (P = 0.17). In conclusion, CB chemosensitivity was not attenuated during the cold stress diving condition and does not appear to contribute to changes in ventilation or CO2 retention.
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Affiliation(s)
- Hayden W Hess
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, New York.,Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
| | - David Hostler
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, New York.,Department of Emergency Medicine, University at Buffalo, Buffalo, New York
| | - Brian M Clemency
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, New York.,Department of Emergency Medicine, University at Buffalo, Buffalo, New York
| | - Erika St James
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, New York.,Department of Emergency Medicine, University at Buffalo, Buffalo, New York
| | - Blair D Johnson
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, New York.,Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana
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Bock JM, Hanson BE, Asama TF, Feider AJ, Hanada S, Aldrich AW, Dyken ME, Casey DP. Acute inorganic nitrate supplementation and the hypoxic ventilatory response in patients with obstructive sleep apnea. J Appl Physiol (1985) 2021; 130:87-95. [PMID: 33211592 DOI: 10.1152/japplphysiol.00696.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Patients with obstructive sleep apnea (OSA) have increased cardiovascular disease risk largely attributable to hypertension. Heightened peripheral chemoreflex sensitivity (i.e., exaggerated responsiveness to hypoxia) facilitates hypertension in these patients. Nitric oxide blunts the peripheral chemoreflex, and patients with OSA have reduced nitric oxide bioavailability. We therefore investigated the dose-dependent effects of acute inorganic nitrate supplementation (beetroot juice), an exogenous nitric oxide source, on blood pressure and cardiopulmonary responses to hypoxia in patients with OSA using a randomized, double-blind, placebo-controlled crossover design. Fourteen patients with OSA (53 ± 10 yr, 29.2 ± 5.8 kg/m2, apnea-hypopnea index = 17.8 ± 8.1, 43%F) completed three visits. Resting brachial blood pressure and cardiopulmonary responses to inspiratory hypoxia were measured before, and 2 h after, acute inorganic nitrate supplementation [∼0.10 mmol (placebo), 4.03 mmol (low dose), and 8.06 mmol (high dose)]. Placebo increased neither plasma [nitrate] (30 ± 52 to 52 ± 23 μM, P = 0.26) nor [nitrite] (266 ± 153 to 277 ± 164 nM, P = 0.21); however, both increased following low (29 ± 17 to 175 ± 42 μM, 220 ± 137 to 514 ± 352 nM) and high doses (26 ± 11 to 292 ± 90 μM, 248 ± 155 to 738 ± 427 nM, respectively, P < 0.01 for all). Following placebo, systolic blood pressure increased (120 ± 9 to 128 ± 10 mmHg, P < 0.05), whereas no changes were observed following low (121 ± 11 to 123 ± 8 mmHg, P = 0.19) or high doses (124 ± 13 to 124 ± 9 mmHg, P = 0.96). The peak ventilatory response to hypoxia increased following placebo (3.1 ± 1.2 to 4.4 ± 2.6 L/min, P < 0.01) but not low (4.4 ± 2.4 to 5.4 ± 3.4 L/min, P = 0.11) or high doses (4.3 ± 2.3 to 4.8 ± 2.7 L/min, P = 0.42). Inorganic nitrate did not change the heart rate responses to hypoxia (beverage-by-time P = 0.64). Acute inorganic nitrate supplementation appears to blunt an early-morning rise in systolic blood pressure potentially through suppression of peripheral chemoreflex sensitivity in patients with OSA.NEW & NOTEWORTHY The present study is the first to examine the acute effects of inorganic nitrate supplementation on resting blood pressure and cardiopulmonary responses to hypoxia (e.g., peripheral chemoreflex sensitivity) in patients with obstructive sleep apnea (OSA). Our data indicate inorganic nitrate supplementation attenuates an early-morning rise in systolic blood pressure potentially attributable to blunted peripheral chemoreflex sensitivity. These data show proof-of-concept that inorganic nitrate supplementation could reduce the risk of cardiovascular disease in patients with OSA.
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Affiliation(s)
- Joshua M Bock
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Brady E Hanson
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Thomas F Asama
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Andrew J Feider
- Department of Anesthesia, University of Iowa, Iowa City, Iowa
| | - Satoshi Hanada
- Department of Anesthesia, University of Iowa, Iowa City, Iowa
| | - Aric W Aldrich
- Department of Anesthesia, University of Iowa, Iowa City, Iowa
| | - Mark Eric Dyken
- Department of Neurology, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Darren P Casey
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa
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9
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Khalefah MM, Khalifah AM. Determining the relationship between SARS-CoV-2 infection, dopamine, and COVID-19 complications. J Taibah Univ Med Sci 2020; 15:550-553. [PMID: 33173452 PMCID: PMC7646371 DOI: 10.1016/j.jtumed.2020.10.006] [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: 05/15/2020] [Revised: 10/15/2020] [Accepted: 10/18/2020] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVES There is compelling evidence that aged, immunosuppressed, and chronically ill patients are a high-risk group for increased mortality upon infection with the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This study investigated the contribution of morbidities and related prescribed medications to COVID-19 associated mortality. METHODS Based on the various recently reported clinical scenarios a theoretical framework was designed to shed light on the mode of infection of the central nervous system by SARS-CoV-2 and possible management options. RESULTS Dopamine-release mechanisms in the central nervous system may play a major role in the entry and propagation of coronaviruses. CONCLUSION This study emphasizes the need for a thorough and urgent investigation of the dopamine-release pathways in the central nervous system. These efforts will help find a definitive cure for the pandemic coronavirus disease (COVID-19).
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Affiliation(s)
- Muad M. Khalefah
- Department of Biology, King Abdulaziz University, CSAR, Rabigh, KSA
| | - Ayman M. Khalifah
- Department of Dental Education, Taibah University College of Dentistry, Almadinah Almunawwarah, KSA
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10
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Jacob DW, Ott EP, Baker SE, Scruggs ZM, Ivie CL, Harper JL, Manrique-Acevedo CM, Limberg JK. Sex differences in integrated neurocardiovascular control of blood pressure following acute intermittent hypercapnic hypoxia. Am J Physiol Regul Integr Comp Physiol 2020; 319:R626-R636. [PMID: 32966122 DOI: 10.1152/ajpregu.00191.2020] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Repetitive hypoxic apneas, similar to those observed in sleep apnea, result in resetting of the sympathetic baroreflex to higher blood pressures (BP). This baroreflex resetting is associated with hypertension in preclinical models of sleep apnea (intermittent hypoxia, IH); however, the majority of understanding comes from males. There are data to suggest that female rats exposed to IH do not develop high BP. Clinical data further support sex differences in the development of hypertension in sleep apnea, but mechanistic data are lacking. Here we examined sex-related differences in the effect of IH on sympathetic control of BP in humans. We hypothesized that after acute IH we would observe a rise in muscle sympathetic nerve activity (MSNA) and arterial BP in young men (n = 30) that would be absent in young women (n = 19). BP and MSNA were measured during normoxic rest before and after 30 min of IH. Baroreflex sensitivity (modified Oxford) was evaluated before and after IH. A rise in mean BP following IH was observed in men (+2.0 ± 0.7 mmHg, P = 0.03), whereas no change was observed in women (-2.7 ± 1.2 mmHg, P = 0.11). The elevation in MSNA following IH was not different between groups (4.7 ± 1.1 vs. 3.8 ± 1.2 bursts/min, P = 0.65). Sympathetic baroreflex sensitivity did not change after IH in either group (P > 0.05). Our results support sex-related differences in the effect of IH on neurovascular control of BP and show that any BP-raising effects of IH are absent in young women. These data enhance our understanding of sex-specific mechanisms that may contribute to BP changes in sleep apnea.
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Affiliation(s)
- Dain W Jacob
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Elizabeth P Ott
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Sarah E Baker
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | | | - Clayton L Ivie
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Jennifer L Harper
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Camila M Manrique-Acevedo
- Department of Medicine, University of Missouri, Columbia, Missouri.,Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
| | - Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri.,Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
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11
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Aldossary HS, Alzahrani AA, Nathanael D, Alhuthail EA, Ray CJ, Batis N, Kumar P, Coney AM, Holmes AP. G-Protein-Coupled Receptor (GPCR) Signaling in the Carotid Body: Roles in Hypoxia and Cardiovascular and Respiratory Disease. Int J Mol Sci 2020; 21:ijms21176012. [PMID: 32825527 PMCID: PMC7503665 DOI: 10.3390/ijms21176012] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 08/13/2020] [Accepted: 08/16/2020] [Indexed: 12/17/2022] Open
Abstract
The carotid body (CB) is an important organ located at the carotid bifurcation that constantly monitors the blood supplying the brain. During hypoxia, the CB immediately triggers an alarm in the form of nerve impulses sent to the brain. This activates protective reflexes including hyperventilation, tachycardia and vasoconstriction, to ensure blood and oxygen delivery to the brain and vital organs. However, in certain conditions, including obstructive sleep apnea, heart failure and essential/spontaneous hypertension, the CB becomes hyperactive, promoting neurogenic hypertension and arrhythmia. G-protein-coupled receptors (GPCRs) are very highly expressed in the CB and have key roles in mediating baseline CB activity and hypoxic sensitivity. Here, we provide a brief overview of the numerous GPCRs that are expressed in the CB, their mechanism of action and downstream effects. Furthermore, we will address how these GPCRs and signaling pathways may contribute to CB hyperactivity and cardiovascular and respiratory disease. GPCRs are a major target for drug discovery development. This information highlights specific GPCRs that could be targeted by novel or existing drugs to enable more personalized treatment of CB-mediated cardiovascular and respiratory disease.
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Affiliation(s)
- Hayyaf S. Aldossary
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- College of Medicine, Basic Medical Sciences, King Saud bin Abdulaziz University for Health Sciences, Riyadh 11481, Saudi Arabia
| | - Abdulaziz A. Alzahrani
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- Respiratory Care Department, Faculty of Applied Medical Sciences, Umm Al-Qura University, Makkah 24381, Saudi Arabia
| | - Demitris Nathanael
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Eyas A. Alhuthail
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- Collage of Sciences and Health Professions, Basic Sciences Department, King Saud bin Abdulaziz University for Health Sciences, Riyadh 11481, Saudi Arabia
| | - Clare J. Ray
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Nikolaos Batis
- Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham B15 2TT, UK;
| | - Prem Kumar
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Andrew M. Coney
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
| | - Andrew P. Holmes
- Institute of Clinical Sciences, University of Birmingham, Birmingham B15 2TT, UK; (H.S.A.); (A.A.A.); (D.N.); (E.A.A.); (C.J.R.); (P.K.); (A.M.C.)
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham B15 2TT, UK
- Correspondence: ; Tel.: +44-121-415-8161
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12
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Hess HW, Hostler D, Clemency BM, Johnson BD. Carotid body chemosensitivity at 1.6 ATA breathing air versus 100% oxygen. J Appl Physiol (1985) 2020; 129:247-256. [PMID: 32584669 DOI: 10.1152/japplphysiol.00275.2020] [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] [Indexed: 12/12/2022] Open
Abstract
Hyperoxia reduces the ventilatory response to hypercapnia by suppressing carotid body (CB) activation. This effect may contribute to CO2 retention during underwater diving due to the high arterial O2 content associated with hyperbaria. We tested the hypothesis that CB chemosensitivity to hypercapnia and hypoxia is attenuated during hyperbaria. Ten subjects completed two, 4-h dry dives at 1.6 atmosphere absolute (ATA) breathing either 21% O2 (Air) or 100% O2 (100% O2). CB chemosensitivity was assessed using brief hypercapnic ventilatory response ([Formula: see text]) and hypoxic ventilatory response ([Formula: see text]) tests predive, 75 and 155 min into the dives, and 15 and 55 min postdive. End-tidal CO2 pressure increased during the dive at 75 and 155 min [Air: +9 (SD 4) mmHg and +8 (SD 4) mmHg versus 100% O2: +6 (SD 4) mmHg and +5 (SD 3) mmHg; all P < 0.01] and was higher while breathing Air (P < 0.01). [Formula: see text] was unchanged during the dive (P = 0.73) and was not different between conditions (P = 0.47). However, [Formula: see text] was attenuated from predive during the dive at 155 min breathing Air [-0.035 (SD 0.037) L·min·mmHg-1; P = 0.02] and at both time points while breathing 100% O2 [-0.035 (SD 0.052) L·min·mmHg-1 and -0.034 (SD 0.064) L·min·mmHg-1; P = 0.02 and P = 0.02, respectively]. These data indicate that the CB chemoreceptors do not appear to contribute to CO2 retention in hyperbaria.NEW & NOTEWORTHY We demonstrate that carotid body chemosensitivity to brief exposures of hypercapnia was unchanged during a 4-h dive in a dry hyperbaric chamber at 1.6 ATA regardless of breathing gas condition [i.e., air (21% O2) versus 100% oxygen]. Therefore, it appears that an attenuation of carotid body chemosensitivity to hypercapnia does not contribute to CO2 retention in hyperbaria.
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Affiliation(s)
- Hayden W Hess
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - David Hostler
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Brian M Clemency
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York.,Department of Emergency Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York
| | - Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
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13
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Collins SÉ, Phillips DB, McMurtry MS, Bryan TL, Paterson DI, Wong E, Ezekowitz JA, Forhan MA, Stickland MK. The Effect of Carotid Chemoreceptor Inhibition on Exercise Tolerance in Chronic Heart Failure. Front Physiol 2020; 11:195. [PMID: 32226392 PMCID: PMC7080702 DOI: 10.3389/fphys.2020.00195] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 02/20/2020] [Indexed: 12/14/2022] Open
Abstract
Purpose Chronic heart failure (CHF) is characterized by heightened sympathetic nervous activity, carotid chemoreceptor (CC) sensitivity, marked exercise intolerance and an exaggerated ventilatory response to exercise. The purpose of this study was to determine the effect of CC inhibition on exercise cardiovascular and ventilatory function, and exercise tolerance in health and CHF. Methods Twelve clinically stable, optimally treated patients with CHF (mean ejection fraction: 43 ± 2.5%) and 12 age- and sex-matched healthy controls were recruited. Participants completed two time-to-symptom-limitation (TLIM) constant load cycling exercise tests at 75% peak power output with either intravenous saline or low-dose dopamine (2 μg⋅kg–1⋅min–1; order randomized). Ventilation was measured using expired gas data and operating lung volume data were determined during exercise by inspiratory capacity maneuvers. Cardiac output was estimated using impedance cardiography, and vascular conductance was calculated as cardiac output/mean arterial pressure. Results There was no change in TLIM in either group with dopamine (CHF: saline 13.1 ± 2.4 vs. dopamine 13.5 ± 1.6 min, p = 0.78; Control: saline 10.3 ± 1.2 vs. dopamine 11.5 ± 1.3 min, p = 0.16). In CHF patients, dopamine increased cardiac output (p = 0.03), vascular conductance (p = 0.01) and oxygen delivery (p = 0.04) at TLIM, while ventilatory parameters were unaffected (p = 0.76). In controls, dopamine improved vascular conductance at TLIM (p = 0.03), but no other effects were observed. Conclusion Our findings suggest that the CC contributes to cardiovascular regulation during full-body exercise in patients with CHF, however, CC inhibition does not improve exercise tolerance.
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Affiliation(s)
- Sophie É Collins
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.,Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
| | - Devin B Phillips
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.,Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, AB, Canada
| | - M Sean McMurtry
- Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Tracey L Bryan
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - D Ian Paterson
- Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Eric Wong
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Justin A Ezekowitz
- Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Mary A Forhan
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
| | - Michael K Stickland
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.,G.F. MacDonald Centre for Lung Health, Covenant Health, Edmonton, AB, Canada
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14
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Testing individual baroreflex responses to hypoxia-induced peripheral chemoreflex stimulation. Clin Auton Res 2020; 30:531-540. [PMID: 31974825 PMCID: PMC7704522 DOI: 10.1007/s10286-019-00660-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 12/21/2019] [Indexed: 12/24/2022]
Abstract
Introduction Baroreflexes and peripheral chemoreflexes control efferent autonomic activity making these reflexes treatment targets for arterial hypertension. The literature on their interaction is controversial, with suggestions that their individual and collective influence on blood pressure and heart rate regulation is variable. Therefore, we applied a study design that allows the elucidation of individual baroreflex–chemoreflex interactions. Methods We studied nine healthy young men who breathed either normal air (normoxia) or an air–nitrogen–carbon dioxide mixture with decreased oxygen content (hypoxia) for 90 min, with randomization to condition, followed by a 30-min recovery period and then exposure to the other condition for 90 min. Multiple intravenous phenylephrine bolus doses were applied per condition to determine phenylephrine pressor sensitivity as an estimate of baroreflex blood pressure buffering and cardiovagal baroreflex sensitivity (BRS). Results Hypoxia reduced arterial oxygen saturation from 98.1 ± 0.4 to 81.0 ± 0.4% (p < 0.001), raised heart rate from 62.9 ± 2.1 to 76.0 ± 3.6 bpm (p < 0.001), but did not change systolic blood pressure (p = 0.182). Of the nine subjects, six had significantly lower BRS in hypoxia (p < 0.05), two showed a significantly decreased pressor response, and three showed a significantly increased pressor response to phenylephrine in hypoxia, likely through reduced baroreflex buffering (p < 0.05). On average, hypoxia decreased BRS by 6.4 ± 0.9 ms/mmHg (19.9 ± 2.0 vs. 14.12 ± 1.6 ms/mmHg; p < 0.001) but did not change the phenylephrine pressor response (p = 0.878). Conclusion We applied an approach to assess individual baroreflex–chemoreflex interactions in human subjects. A subgroup exhibited significant impairments in baroreflex blood pressure buffering and BRS with peripheral chemoreflex activation. The methodology may have utility in elucidating individual pathophysiology and in targeting treatments modulating baroreflex or chemoreflex function.
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15
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Limberg JK, Johnson BD, Mozer MT, Holbein WW, Curry TB, Prabhakar NR, Joyner MJ. Role of the carotid chemoreceptors in insulin-mediated sympathoexcitation in humans. Am J Physiol Regul Integr Comp Physiol 2019; 318:R173-R181. [PMID: 31746629 DOI: 10.1152/ajpregu.00257.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined the contribution of the carotid chemoreceptors to insulin-mediated increases in muscle sympathetic nerve activity (MSNA) in healthy humans. We hypothesized that reductions in carotid chemoreceptor activity would attenuate the sympathoexcitatory response to hyperinsulinemia. Young, healthy adults (9 male/9 female, 28 ± 1 yr, 24 ± 1 kg/m2) completed a 30-min euglycemic baseline followed by a 90-min hyperinsulinemic (1 mU·kg fat-free mass-1·min-1), euglycemic infusion. MSNA (microneurography of the peroneal nerve) was continuously measured. The role of the carotid chemoreceptors was assessed at baseline and during hyperinsulinemia via 1) acute hyperoxia, 2) low-dose dopamine (1-4 µg·kg-1·min-1), and 3) acute hyperoxia + low-dose dopamine. MSNA burst frequency increased from baseline during hyperinsulinemia (P < 0.01). Acute hyperoxia had no effect on MSNA burst frequency at rest (P = 0.74) or during hyperinsulinemia (P = 0.83). The insulin-mediated increase in MSNA burst frequency (P = 0.02) was unaffected by low-dose dopamine (P = 0.60). When combined with low-dose dopamine, acute hyperoxia had no effect on MSNA burst frequency at rest (P = 0.17) or during hyperinsulinemia (P = 0.85). Carotid chemoreceptor desensitization in young, healthy men and women does not attenuate the sympathoexcitatory response to hyperinsulinemia. Our data suggest that the carotid chemoreceptors do not contribute to acute insulin-mediated increases in MSNA in young, healthy adults.
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Affiliation(s)
- Jacqueline K Limberg
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota.,Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Blair D Johnson
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota.,Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Michael T Mozer
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | | | - Timothy B Curry
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | - Nanduri R Prabhakar
- Institute for Integrative Physiology, School of Medicine, University of Chicago, Chicago, Illinois
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16
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Phillips DB, Collins SÉ, Bryan TL, Wong EYL, McMurtry MS, Bhutani M, Stickland MK. The effect of carotid chemoreceptor inhibition on exercise tolerance in chronic obstructive pulmonary disease: A randomized-controlled crossover trial. Respir Med 2019; 160:105815. [PMID: 31739245 DOI: 10.1016/j.rmed.2019.105815] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 10/24/2019] [Accepted: 11/05/2019] [Indexed: 11/19/2022]
Abstract
BACKGROUND Patients with chronic obstructive pulmonary disease (COPD) have an exaggerated ventilatory response to exercise, contributing to exertional dyspnea and exercise intolerance. We recently demonstrated enhanced activity and sensitivity of the carotid chemoreceptor (CC) in COPD which may alter ventilatory and cardiovascular regulation and negatively affect exercise tolerance. We sought to determine whether CC inhibition improves ventilatory and cardiovascular regulation, dyspnea and exercise tolerance in COPD. METHODS Twelve mild-moderate COPD patients (FEV1 83 ± 15 %predicted) and twelve age- and sex-matched healthy controls completed two time-to-symptom limitation (TLIM) constant load exercise tests at 75% peak power output with either intravenous saline or low-dose dopamine (2 μg·kg-1·min-1, order randomized) to inhibit the CC. Ventilatory responses were evaluated using expired gas data and dyspnea was evaluated using a modified Borg scale. Inspiratory capacity maneuvers were performed to determine operating lung volumes. Cardiac output was estimated using impedance cardiography and vascular conductance was calculated as cardiac output/mean arterial pressure (MAP). RESULTS At a standardized exercise time of 4-min and at TLIM; ventilation, operating volumes and dyspnea were unaffected by dopamine in COPD patients and controls. In COPD, dopamine decreased MAP and increased vascular conductance at all time points. In controls, dopamine increased vascular conductance at TLIM, while MAP was unaffected. CONCLUSION There was no change in time to exhaustion in either group with dopamine. These data suggest that the CC plays a role in cardiovascular regulation during exercise in COPD; however, ventilation, dyspnea and exercise tolerance were unaffected by CC inhibition in COPD patients.
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Affiliation(s)
- Devin B Phillips
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Canada; Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Canada
| | - Sophie É Collins
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Canada; Faculty of Rehabilitation Medicine, University of Alberta, Canada
| | - Tracey L Bryan
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Canada
| | - Eric Y L Wong
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Canada
| | - M Sean McMurtry
- Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Canada
| | - Mohit Bhutani
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Canada
| | - Michael K Stickland
- Division of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Canada; G.F. MacDonald Centre for Lung Health, Covenant Health, Edmonton, Alberta, Canada.
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17
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Ott EP, Baker SE, Holbein WW, Shoemaker JK, Limberg JK. Effect of varying chemoreflex stress on sympathetic neural recruitment strategies during apnea. J Neurophysiol 2019; 122:1386-1396. [PMID: 31389742 DOI: 10.1152/jn.00319.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We sought to examine the effect of varying chemoreflex stress on sympathetic neural recruitment strategies during end-expiratory apnea. We hypothesized that increases in the firing frequency and probability of low-threshold axons at the asphyxic "break point" would be exaggerated during hypoxia and attenuated during hyperoxia. Multiunit muscle sympathetic nervous system activity (MSNA) (peroneal nerve microneurography) was measured in 10 healthy male subjects (31 ± 2 yr, 25 ± 1 kg/m2). Individuals completed maximal voluntary end-expiratory apnea under normoxic, hypoxic (inspired O2 fraction: 0.17 ± 0.01), and hyperoxic (inspired O2 fraction: 0.92 ± 0.03) conditions. Action potential (AP) patterns were examined from the filtered raw signal with wavelet-based methodology. Multiunit MSNA was increased (P ≤ 0.05) during normoxic apnea, because of an increase in the frequency and incidence of AP spikes (243 ± 75 to 519 ± 134 APs/min, P = 0.048; 412 ± 133 to 733 ± 185 APs/100 heartbeats, P = 0.02). Multiunit MSNA increased from baseline (P < 0.01) during hypoxic apnea, which was due to an increase in the frequency and incidence of APs (192 ± 59 to 952 ± 266 APs/min, P < 0.01; 326 ± 89 to 1,212 ± 327 APs/100 heartbeats, P < 0.01). Hypoxic apnea also resulted in an increase in the probability of a particular AP cluster firing more than once per burst (P < 0.01). Hyperoxia attenuated any increase in MSNA with apnea, such that no changes in multiunit MSNA or frequency or incidence of AP spikes were observed (P > 0.05). We conclude that increases in frequency and incidence of APs during apnea are potentiated during hypoxia and suppressed when individuals are hyperoxic, highlighting the important impact of chemoreflex stress in AP discharge patterns. The results may have implications for neural control of the circulation in recreational activities and/or clinical conditions prone to apnea.NEW & NOTEWORTHY Our results demonstrate that, compared with normoxic end-expiratory apnea, hypoxic apnea increases the frequency and incidence of action potential spikes as well as the probability of multiple firing. We further show that this response is suppressed when individuals are hyperoxic. These data highlight the potentially important role of chemoreflex stress in neural firing and recruitment and may have implications for neural control of the circulation in recreational and/or clinical conditions prone to apnea.
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Affiliation(s)
- Elizabeth P Ott
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Sarah E Baker
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Walter W Holbein
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
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18
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Sackett JR, Schlader ZJ, Sarker S, Chapman CL, Johnson BD. Peripheral chemosensitivity is not blunted during 2 h of thermoneutral head out water immersion in healthy men and women. Physiol Rep 2018; 5:5/20/e13472. [PMID: 29051306 PMCID: PMC5661233 DOI: 10.14814/phy2.13472] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 09/17/2017] [Indexed: 11/24/2022] Open
Abstract
Carbon dioxide (CO2) retention occurs during water immersion, but it is not known if peripheral chemosensitivity is altered during water immersion, which could contribute to CO2 retention. We tested the hypothesis that peripheral chemosensitivity to hypercapnia and hypoxia is blunted during 2 h of thermoneutral head out water immersion (HOWI) in healthy young adults. Peripheral chemosensitivity was assessed by the ventilatory, heart rate, and blood pressure responses to hypercapnia and hypoxia at baseline, 10, 60, 120 min, and post HOWI and a time‐control visit (control). Subjects inhaled 1 breath of 13% CO2, 21% O2, and 66% N2 to test peripheral chemosensitivity to hypercapnia and 2–6 breaths of 100% N2 to test peripheral chemosensitivity to hypoxia. Each gas was administered four separate times at each time point. Partial pressure of end‐tidal CO2 (PETCO2), arterial oxygen saturation (SpO2), ventilation, heart rate, and blood pressure were recorded continuously. Ventilation was higher during HOWI versus control at post (P = 0.037). PETCO2 was higher during HOWI versus control at 10 min (46 ± 2 vs. 44 ± 2 mmHg), 60 min (46 ± 2 vs. 44 ± 2 mmHg), and 120 min (46 ± 3 vs. 43 ± 3 mmHg) (all P < 0.001). Ventilatory (P = 0.898), heart rate (P = 0.760), and blood pressure (P = 0.092) responses to hypercapnia were not different during HOWI versus control at any time point. Ventilatory (P = 0.714), heart rate (P = 0.258), and blood pressure (P = 0.051) responses to hypoxia were not different during HOWI versus control at any time point. These data indicate that CO2 retention occurs during thermoneutral HOWI despite no changes in peripheral chemosensitivity.
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Affiliation(s)
- James R Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Zachary J Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Suman Sarker
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Christopher L Chapman
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
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19
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Abstract
Known primarily for its oxygen-sensing capabilities, the carotid body chemoreceptors have recently been implicated, primarily by work in animal models, in the pathophysiology of a number of metabolic conditions. The research presented in this brief review highlights translational work conducted at the Mayo Clinic between 2010 and 2017 in healthy humans and discusses key areas for future work in disease populations.
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Affiliation(s)
- Jacqueline K Limberg
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota and Department of Nutrition and Exercise Physiology, University of Missouri , Columbia, Missouri
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20
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Barbosa TC, Kaur J, Holwerda SW, Young CN, Curry TB, Thyfault JP, Joyner MJ, Limberg JK, Fadel PJ. Insulin increases ventilation during euglycemia in humans. Am J Physiol Regul Integr Comp Physiol 2018; 315:R84-R89. [PMID: 29590558 DOI: 10.1152/ajpregu.00039.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Evidence from animal studies indicates that hyperinsulinemia, without changes in glucose, increases ventilation via a carotid body-mediated mechanism. However, whether insulin elevates ventilation in humans independently of changes in glucose remains unclear. Therefore, we tested the hypothesis that insulin increases ventilation in humans during a hyperinsulinemic-euglycemic clamp in which insulin was elevated to postprandial concentrations while glucose was maintained at fasting concentrations. First, in 16 healthy young men ( protocol 1), we retrospectively analyzed respiration rate and estimated tidal volume from a pneumobelt to calculate minute ventilation during a hyperinsulinemic-euglycemic clamp. In addition, for a direct assessment of minute ventilation during a hyperinsulinemic-euglycemic clamp, we retrospectively analyzed breath-by-breath respiration rate and tidal volume from inspired/expired gasses in an additional 23 healthy young subjects ( protocol 2). Clamp infusion elevated minute ventilation from baseline in both protocols ( protocol 1: +11.9 ± 4.6% baseline, P = 0.001; protocol 2: +9.5 ± 3.8% baseline, P = 0.020). In protocol 1, peak changes in both respiration rate (+13.9 ± 3.0% baseline, P < 0.001) and estimated tidal volume (+16.9 ± 4.1% baseline, P = 0.001) were higher than baseline during the clamp. In protocol 2, tidal volume primarily increased during the clamp (+9.7 ± 3.7% baseline, P = 0.016), as respiration rate did not change significantly (+0.2 ± 1.8% baseline, P = 0.889). Collectively, we demonstrate for the first time in humans that elevated plasma insulin increases minute ventilation independent of changes in glucose.
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Affiliation(s)
- Thales C Barbosa
- Department of Kinesiology, University of Texas Arlington , Arlington, Texas
| | - Jasdeep Kaur
- Department of Kinesiology, University of Texas Arlington , Arlington, Texas
| | - Seth W Holwerda
- Department of Health and Human Physiology, University of Iowa , Iowa City, Iowa
| | - Colin N Young
- Department of Pharmacology & Physiology, George Washington University School of Medicine and Health Sciences , Washington, District of Columbia
| | - Timothy B Curry
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
| | - John P Thyfault
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center , Kansas City, Kansas
| | - Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
| | - Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri , Columbia, Missouri
| | - Paul J Fadel
- Department of Kinesiology, University of Texas Arlington , Arlington, Texas
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21
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Joyner MJ, Limberg JK, Wehrwein EA, Johnson BD. Role of the carotid body chemoreceptors in glucose homeostasis and thermoregulation in humans. J Physiol 2018; 596:3079-3085. [PMID: 29377157 DOI: 10.1113/jp274354] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 01/02/2018] [Indexed: 01/03/2023] Open
Abstract
The carotid bodies (CBs) are multi-modal sensory organs located bilaterally at the bifurcation of the carotid artery and innervated by the carotid sinus nerve (Hering's nerve), a branch of the IX cranial nerve. While the CBs (or embryologically analogous structures) are well known as the dominant oxygen-sensing organ in vertebrates, in mammals there is evidence that the CBs may also sense glucose and temperature, and respond to circulating hormones and other factors. Additionally, the CBs likely participate in regulating baseline levels of sympathetic tone. In this brief review, we focus on the evolution of our efforts to understand 'what else' beyond oxygen sensing the CBs do in humans.
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Affiliation(s)
- Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211, USA
| | - Erica A Wehrwein
- Department of Physiology, Michigan State University, East Lansing, MI 48823, USA
| | - Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA
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22
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Fisher JP, Flück D, Hilty MP, Lundby C. Carotid chemoreceptor control of muscle sympathetic nerve activity in hypobaric hypoxia. Exp Physiol 2017; 103:77-89. [DOI: 10.1113/ep086493] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 10/12/2017] [Indexed: 12/16/2022]
Affiliation(s)
- James P. Fisher
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences; University of Birmingham; Edgbaston Birmingham UK
| | - Daniela Flück
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences; University of British Columbia - Okanagan; Kelowna British Columbia Canada
- Zurich Center for Integrative Human Physiology (ZIHP), Institute of Physiology; University of Zurich; Switzerland
| | - Matthias P. Hilty
- Intensive Care Unit; University Hospital of Zürich; Zürich Switzerland
| | - Carsten Lundby
- Zurich Center for Integrative Human Physiology (ZIHP), Institute of Physiology; University of Zurich; Switzerland
- Center for Physical Activity Research (CFAS); University Hospital of Copenhagen; Copenhagen Denmark
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23
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Bock JM, Ueda K, Schneider AC, Hughes WE, Limberg JK, Bryan NS, Casey DP. Inorganic nitrate supplementation attenuates peripheral chemoreflex sensitivity but does not improve cardiovagal baroreflex sensitivity in older adults. Am J Physiol Heart Circ Physiol 2017; 314:H45-H51. [PMID: 28971842 DOI: 10.1152/ajpheart.00389.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Aging is associated with increased peripheral chemoreceptor activity, reduced nitric oxide (NO) bioavailability, and attenuation of cardiovagal baroreflex sensitivity (BRS), collectively increasing the risk of cardiovascular disease. Evidence suggests that NO may attenuate peripheral chemoreflex sensitivity and increase BRS. Exogenous inorganic nitrate ([Formula: see text]) increases NO bioavailability via the [Formula: see text]-[Formula: see text]-NO pathway. Our hypothesis was that inorganic [Formula: see text] supplementation would attenuate peripheral chemoreflex sensitivity and enhance spontaneous cardiovagal BRS in older adults. We used a randomized, placebo-controlled crossover design in which 13 older (67 ± 3 yr old) adults ingested beetroot powder containing (BRA) or devoid of (BRP) [Formula: see text] and [Formula: see text] daily over 4 wk. Spontaneous cardiovagal BRS was assessed over 15 min of rest and was quantified using the sequence method. Chemoreflex sensitivity was assessed via ~5 min of hypoxia (10% fraction of inspired O2) and reported as the slope of the relationship between O2 saturation (%[Formula: see text]) and minute ventilation (in l/min) or heart rate (in beats/min). Ventilatory responsiveness to hypoxia was reduced after BRA (from -0.14 ± 0.04 to -0.05 ± 0.02 l·min-1·%[Formula: see text]-1, P = 0.01) versus BRP (from -0.10 ± 0.05 to -0.11 ± 0.05 l·min-1·%[Formula: see text]-1, P = 0.80), with no differences in heart rate responsiveness (BRA: from -0.47 ± 0.06 to -0.33 ± 0.04 beats·min-1·%[Formula: see text]-1, BRP: from -0.48 ± 0.07 to -0.42 ± 0.06 beats·min-1·%[Formula: see text]-1) between conditions (interaction effect, P = 0.41). Spontaneous cardiovagal BRS was unchanged after BRA and BRP (interaction effects, P = 0.69, 0.94, and 0.39 for all, up, and down sequences, respectively), despite a reduction in resting systolic and mean arterial blood pressure in the experimental (BRA) group ( P < 0.01 for both). These findings illustrate that inorganic [Formula: see text] supplementation attenuates peripheral chemoreflex sensitivity without concomitant change in spontaneous cardiovagal BRS in older adults. NEW & NOTEWORTHY Exogenous inorganic nitrate supplementation attenuates ventilatory, but not heart rate, responsiveness to abbreviated hypoxic exposure in older adults. Additionally, inorganic nitrate reduces systolic and mean arterial blood pressure without affecting spontaneous cardiovagal baroreflex sensitivity. These findings suggest that inorganic nitrate may attenuate sympathetically oriented pathologies associated with aging.
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Affiliation(s)
- Joshua M Bock
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa , Iowa City, Iowa
| | - Kenichi Ueda
- Department of Anesthesia, Carver College of Medicine, University of Iowa , Iowa City, Iowa
| | - Aaron C Schneider
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa , Iowa City, Iowa
| | - William E Hughes
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa , Iowa City, Iowa
| | | | - Nathan S Bryan
- Department of Molecular and Human Genetics, Baylor College of Medicine , Houston, Texas
| | - Darren P Casey
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa , Iowa City, Iowa.,Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa , Iowa City, Iowa.,Fraternal Order of Eagles Diabetes Research Center, Carver College of Medicine, University of Iowa , Iowa City, Iowa
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24
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Johnson BD, Peinado AB, Ranadive SM, Curry TB, Joyner MJ. Effects of intravenous low-dose dopamine infusion on glucose regulation during prolonged aerobic exercise. Am J Physiol Regul Integr Comp Physiol 2017; 314:R49-R57. [PMID: 28931543 DOI: 10.1152/ajpregu.00030.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The carotid body chemoreceptors are activated during hypoglycemia and contribute to glucoregulation during prolonged exercise in dogs. Low-dose intravenous infusions of dopamine have been shown to blunt the activation of the carotid body chemoreceptors during hypoxia. Therefore, we tested the hypotheses that dopamine would blunt glucoregulatory responses and attenuate plasma glucose during prolonged aerobic exercise in healthy participants. Twelve healthy participants completed two randomized exercise sessions at 65% peak oxygen consumption for up to 120 min. Saline was infused during one exercise session, and dopamine (2 μg·kg-1·min-1) was infused during the other session. Arterial plasma glucose, growth hormone, glucagon, cortisol, norepinephrine, and epinephrine were measured every 10 min. Exercise duration during dopamine infusion was 107 ± 6 and 119 ± 0.8 min during saline infusion. Glucose area under the curve during exercise was lower during dopamine (9,821 ± 686 vs. 11,194 ± 395 arbitrary units; P = 0.016). The ratio of circulating growth hormone to glucose and the ratio of glucagon to glucose were greater during dopamine ( P = 0.045 and 0.037, respectively). These results indicate that the infusion of dopamine during aerobic exercise impairs glucoregulation. This suggests that the carotid body chemoreceptors contribute to glucoregulation during prolonged exercise in healthy exercise-trained humans.
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Affiliation(s)
- Blair D Johnson
- Department of Anesthesiology, Mayo Clinic , Rochester, Minnesota.,Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Ana B Peinado
- Department of Anesthesiology, Mayo Clinic , Rochester, Minnesota.,LFE Research Group, Department of Health and Human Performance, Universidad Politécnica de Madrid , Madrid , Spain
| | | | - Timothy B Curry
- Department of Anesthesiology, Mayo Clinic , Rochester, Minnesota
| | - Michael J Joyner
- Department of Anesthesiology, Mayo Clinic , Rochester, Minnesota
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25
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Larson KF, Limberg JK, Baker SE, Joyner MJ, Curry TB. Intact blood pressure, but not sympathetic, responsiveness to sympathoexcitatory stimuli in a patient with unilateral carotid body resection. Physiol Rep 2017; 5:5/7/e13212. [PMID: 28364029 PMCID: PMC5392508 DOI: 10.14814/phy2.13212] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 02/22/2017] [Accepted: 02/23/2017] [Indexed: 11/24/2022] Open
Abstract
Despite rapidly growing interest in the therapeutic resection of the carotid body (CB) chemoreceptors, few physiologic studies exist on the consequences of unilateral CB resection. We present a case of an otherwise healthy postmenopausal female who underwent unilateral CB resection for a paraganglioma. Approximately 4 years postoperatively, she underwent analysis of her sympathetic and hemodynamic responses to hypoxia, lower body negative pressure, cold pressor test (CPT), and ischemic hand grip exercise and postexercise ischemia (IHE/PEI). Hypoxic ventilatory response and baroreflex sensitivity were relatively normal. Hemodynamic responses to IHE/PEI and CPT showed characteristic increases in cardiac output (from 3.9 L/min to 5.2 L/min [IHE/PEI] and 4.9 L/min [CPT]) and blood pressure (from 126/72 mmHg to 161/87 mmHg [IHE/PEI] and 171/93 mmHg [CPT]). However, muscle sympathetic nerve activity (microneurography of the peroneal nerve) decreased from baseline during IHE/PEI and CPT (burst incidence nadir of 45% and 40% of baseline, respectively) and there was no observable change in total peripheral resistance (from 24 mmHg*min/L to 22 mmHg*min/L [IHE/PEI] and 25 mmHg*min/L [CPT]). These findings illustrate intact blood pressure responsiveness despite attenuated sympathoexcitation, possibly due to an increase in cardiac output and/or adaptive inhibitory effect of the baroreflex on peripheral sympathetic activity.
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Affiliation(s)
| | | | - Sarah E Baker
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | | | - Timothy B Curry
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
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26
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Mozer MT, Holbein WW, Joyner MJ, Curry TB, Limberg JK. Reductions in carotid chemoreceptor activity with low-dose dopamine improves baroreflex control of heart rate during hypoxia in humans. Physiol Rep 2016; 4:e12859. [PMID: 27418545 PMCID: PMC4945841 DOI: 10.14814/phy2.12859] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/13/2016] [Accepted: 06/18/2016] [Indexed: 11/24/2022] Open
Abstract
The purpose of the present investigation was to examine the contribution of the carotid body chemoreceptors to changes in baroreflex control of heart rate with exposure to hypoxia. We hypothesized spontaneous cardiac baroreflex sensitivity (scBRS) would be reduced with hypoxia and this effect would be blunted when carotid chemoreceptor activity was reduced with low-dose dopamine. Fifteen healthy adults (11 M/4 F) completed two visits randomized to intravenous dopamine or placebo (saline). On each visit, subjects were exposed to 5-min normoxia (~99% SpO2), followed by 5-min hypoxia (~84% SpO2). Blood pressure (intra-arterial catheter) and heart rate (ECG) were measured continuously and scBRS was assessed by spectrum and sequence methodologies. scBRS was reduced with hypoxia (P < 0.01). Using the spectrum analysis approach, the fall in scBRS with hypoxia was attenuated with infusion of low-dose dopamine (P < 0.01). The decrease in baroreflex sensitivity to rising pressures (scBRS "up-up") was also attenuated with low-dose dopamine (P < 0.05). However, dopamine did not attenuate the decrease in baroreflex sensitivity to falling pressures (scBRS "down-down"; P > 0.05). Present findings are consistent with a reduction in scBRS with systemic hypoxia. Furthermore, we show this effect is partially mediated by the carotid body chemoreceptors, given the fall in scBRS is attenuated when activity of the chemoreceptors is reduced with low-dose dopamine. However, the improvement in scBRS with dopamine appears to be specific to rising blood pressures. These results may have important implications for impairments in baroreflex function common in disease states of acute and/or chronic hypoxemia, as well as the experimental use of dopamine to assess such changes.
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Affiliation(s)
- Michael T Mozer
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | | | | | - Timothy B Curry
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
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