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Tusman G, Sipmann FS, Böhm SH. A skeptical look about the existence of the veno-arteriolar reflex. J Physiol 2024; 602:1855-1861. [PMID: 38602858 DOI: 10.1113/jp286490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Accepted: 03/25/2024] [Indexed: 04/13/2024] Open
Affiliation(s)
- Gerardo Tusman
- Department of Anesthesiology, Hospital Privado de Comunidad, Mar del Plata, Buenos Aires, Argentina
| | - Fernando Suarez Sipmann
- Department of Critical Care, Hospital Universitario de La Princesa, Universidad Autonoma de Madrid, Madrid, Spain
- CIBERES, Madrid, Spain
| | - Stephan H Böhm
- Department of Anesthesiology and Intensive Care Medicine, Rostock University Medical Center, Rostock, Germany
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Wang S, Peng Y, Zou R, Wang Y, Cai H, Li F, Luo X, Zhang J, He Z, Wang C. The relationship between demographic factors and syncopal symptom in pediatric vasovagal syncope. Sci Rep 2023; 13:22724. [PMID: 38123593 PMCID: PMC10733366 DOI: 10.1038/s41598-023-49722-w] [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: 09/18/2023] [Accepted: 12/11/2023] [Indexed: 12/23/2023] Open
Abstract
This research proposed to retrospectively analyze 20 years of clinical data and investigate the relationship between demographic factors and syncopal symptom in pediatric vasovagal syncope. A total of 2513 children, 1124 males and 1389 females, age range 3-18 years, who presented to Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University with unexplained syncope or pre-syncope and were diagnosed with vasovagal syncope were retrospectively collected and divided into syncope group (n = 1262) and pre-syncope group (n = 1251). (1) Females had a 36% increased risk of syncope compared to males, a 27% increased risk of syncope for every 1-year increase in age, and a 2% decreased risk of syncope for every 1 cm increase in height. (2) A non-linear relationship between age, height, weight and syncope was observed. When age > 10.67 years, the risk of syncope increases by 45% for each 1-year increase in age; when height < 146 cm, the risk of syncope decreases by 4% for each 1 cm increase in height; when weight < 28.5 kg, the risk of syncope decreases by 10% for each 1 kg increase in weight. Demographic factors are strongly associated with syncopal symptom in pediatric vasovagal syncope and can help to predict the risk.
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Affiliation(s)
- Shuo Wang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China
| | - Yali Peng
- Section of Science and Education, The First People's Hospital of Changde City, Changde, 415000, Hunan, China
| | - Runmei Zou
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China
| | - Yuwen Wang
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China
| | - Hong Cai
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China
| | - Fang Li
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China
| | - Xuemei Luo
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China
| | - Juan Zhang
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China
| | - Zhixiang He
- Department of Pediatrics, Hunan Children's Hospital, Changsha, 410007, Hunan, China
| | - Cheng Wang
- Department of Pediatric Cardiovasology, Children's Medical Center, The Second Xiangya Hospital, Central South University, No.139 Renmin Middle Road, Changsha, 410011, Hunan, China.
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Hamaoka T, Leuenberger UA, Kronfli A, Gao Z, Blaha C, Luck JC, Dalton P, Sinoway LI, Cui J. Effect of Cyclooxygenase Inhibition on Peripheral Venous Distension Reflex in Healthy Humans. Hypertension 2023; 80:1102-1109. [PMID: 36942572 PMCID: PMC10133193 DOI: 10.1161/hypertensionaha.122.20506] [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: 10/19/2022] [Accepted: 03/07/2023] [Indexed: 03/23/2023]
Abstract
BACKGROUND Peripheral venous distension evokes a pressor reflex (venous distension reflex). Afferent group III and IV nerves innervating veins are suggested as the afferent arm of the venous distension reflex. Prostaglandins stimulate/sensitize group III/IV nerves. We hypothesized that inhibition of prostaglandin synthesis by local cyclooxygenase blockade would attenuate the muscle sympathetic nerve activity (MSNA) and blood pressure responses to venous distension. METHODS Nineteen healthy volunteers (age, 27±5 years) participated in the study with 2 visits. To induce venous distension, a volume of solution (saline alone or 9 mg ketorolac tromethamine in saline) was infused into the vein in the antecubital fossa of an arterially occluded forearm. During the procedure, beat-by-beat heart rate, blood pressure and MSNA were recorded simultaneously. The vein size was measured with ultrasound. RESULTS In both visits, the venous distension procedure significantly increased blood pressure, heart rate, and MSNA (all, P<0.05). The increase in mean arterial pressure and MSNA in the ketorolac visit was significantly lower than in the control visit (∆ mean arterial pressure, 7.0±6.2 versus 13.8±7.7 mm Hg; ∆MSNA, 6.0±7.1 versus 14.8±7.7 bursts/min; both, P<0.05). The increase in vein size induced by the infusion was not different between visits. CONCLUSIONS The presented data show that cyclooxygenase blockade attenuates the responses in MSNA and blood pressure to peripheral venous distension reflex. The results suggest that cyclooxygenase products play a key role in evoking afferent activation responsible for the venous distension reflex.
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Affiliation(s)
- Takuto Hamaoka
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Urs A. Leuenberger
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Anthony Kronfli
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Zhaohui Gao
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Cheryl Blaha
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Jonathan Carter Luck
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Paul Dalton
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Lawrence I. Sinoway
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
| | - Jian Cui
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA 17033
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Hamaoka T, Leuenberger UA, Blaha C, Luck JC, Sinoway LI, Cui J. Baroreflex responses to limb venous distension in humans. Am J Physiol Regul Integr Comp Physiol 2022; 323:R267-R276. [PMID: 35726869 PMCID: PMC9359652 DOI: 10.1152/ajpregu.00028.2022] [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
The venous distension reflex (VDR) is a pressor response evoked by peripheral venous distension and accompanied by increased muscle sympathetic nerve activity (MSNA). The effects of venous distension on the baroreflex, an important modulator of blood pressure (BP), has not been examined. The purpose of this study was to examine the effect of the VDR on baroreflex sensitivity (BRS). We hypothesized that the VDR will increase the sympathetic BRS (SBRS). Beat-by-beat heart rate (HR), BP and MSNA were recorded in 16 female and 19 male young healthy subjects. To induce venous distension, normal saline equivalent to 5% of the forearm volume was infused into the veins of the occluded forearm. SBRS was assessed from the relationship between diastolic BP and MSNA during spontaneous BP variations. Cardiovagal BRS (CBRS) was assessed with the sequence technique. Venous distension evoked significant increases in BP and MSNA. Compared to baseline, during the maximal VDR response period, SBRS was significantly increased (-3.1 ± 1.5 to -4.5 ± 1.6 bursts・100 heartbeat-1・mmHg-1, P < 0.01) and CBRS was significantly decreased (16.6 ± 5.4 to 13.8 ± 6.1 ms・mmHg-1, P < 0.01). No sex differences were observed in the effect of the VDR on SBRS or CBRS. These results indicate that in addition to its pressor effect, the VDR altered both SBRS and CBRS. We speculate that these changes in baroreflex function contribute to the modulation of MSNA and BP during limb venous distension.
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Affiliation(s)
- Takuto Hamaoka
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Urs A Leuenberger
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Cheryl Blaha
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Jonathan Carter Luck
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Lawrence I Sinoway
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, United States
| | - Jian Cui
- Penn State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, PA, United States
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Chen K, Du K, Zhao Y, Gu Y, Zhao Y. Trajectory Analysis of Orthostatic Hypotension in Parkinson's Disease: Results From Parkinson's Progression Markers Initiative Cohort. Front Aging Neurosci 2022; 13:762759. [PMID: 34987376 PMCID: PMC8720927 DOI: 10.3389/fnagi.2021.762759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 11/08/2021] [Indexed: 11/13/2022] Open
Abstract
Background: Orthostatic hypotension (OH) in Parkinson’s disease (PD) can lead to falls, impair quality of life, and increase mortality. A trajectory analysis of OH could be useful to predict and prevent the hypotension incidence early. Methods: The longitudinal data of 660 patients with PD with disease duration up to 12 years were extracted from an integrated PD database. We used latent class mixed modeling (LCMM) to identify patient subgroups, demonstrating trajectories of changes in orthostatic blood pressure (BP) over time. The optimal number of subgroups was selected by several criteria including the Bayesian Information Criterion. Baseline information comparison between groups and backward stepwise logistic regression were conducted to define the distinguishing characteristics of these subgroups and to investigate the predictors for BP trajectory. Results: We identified three trajectories for each orthostatic change of systolic blood pressure (ΔSBP), namely, Class 1 (i.e., the increasing class) consisted of 18 participants with low ΔSBP that increased continuously during the follow-up; Class 2 (i.e., the low-stable class) consisted of 610 participants with low ΔSBP that remained low throughout the follow-up; and Class 3 (i.e., the high-stable class) consisted of 32 participants with high ΔSBP at baseline that was relatively stable throughout the follow-up. Several parameters differed among subgroups, but only male sex [odds ratio (OR) = 4.687, 95% confidence interval (CI) = 1.024–21.459], lower supine diastolic blood pressure (DBP) (OR = 0.934, 95% CI = 0.876–0.996), and lower level of total protein at baseline (OR = 0.812, 95% CI = 0.700–0.941) were significant predictors of an increasing ΔSBP trajectory. Conclusion: This study provides new information on the longitudinal development of ΔSBP in patients with PD with distinct trajectories of rapidly increasing, low-stable, and high-stable class. The parameters such as male sex, lower supine DBP, and lower total proteins help to identify the rapidly increasing class.
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Affiliation(s)
- Kui Chen
- Department of Neurology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Kangshuai Du
- Department of Neurology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Yichen Zhao
- Department of Neurology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Yongzhe Gu
- Department of Neurology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Yanxin Zhao
- Department of Neurology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China
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Cui J, Blaha C, Leuenberger UA, Sinoway LI. Sympathetic activation due to limb venous distension is preserved during muscle metaboreceptor stimulation. Am J Physiol Regul Integr Comp Physiol 2021; 321:R21-R28. [PMID: 33978490 DOI: 10.1152/ajpregu.00305.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Venous saline infusions in an arterially occluded forearm evoke reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in humans (venous distension reflex). It is unclear if the inputs from metabolically sensitive skeletal muscle afferents (i.e., muscle metaboreflex) would modify the venous distension reflex. We hypothesized that muscle metaboreceptor stimulation might augment the venous distension reflex. BP (Finapres), heart rate (ECG), and MSNA (microneurography) were assessed in 18 young healthy subjects. In trial A, saline (5% forearm volume) was infused into the veins of an arterially occluded arm (nonhandgrip trial). In trial B, subjects performed 2-min static handgrip followed by postexercise circulatory occlusion (PECO) of the arm. During PECO, saline was infused into the veins of the arm (handgrip trial). In trial A, the infusion increased MSNA and BP as expected (both P < 0.001). In trial B, handgrip significantly raised MSNA, BP, and venous lactic acid concentrations. Venous saline infusion during PECO further raised MSNA and BP (both P < 0.001). The changes in MSNA (Δ8.6 ± 1.5 to Δ10.6 ± 1.8 bursts/min, P = 0.258) and mean arterial pressure (P = 0.844) evoked by the infusion during PECO were not significantly different from those in the nonhandgrip trial. These observations indicate that venous distension reflex responses are preserved during sympathetic activation mediated by the muscle metaboreflex.
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Affiliation(s)
- Jian Cui
- Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Cheryl Blaha
- Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Urs A Leuenberger
- Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Lawrence I Sinoway
- Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
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Alali MH, Vianna LC, Lucas RAI, Junejo RT, Fisher JP. Impact of whole body passive heat stress and arterial shear rate modification on radial artery function in young men. J Appl Physiol (1985) 2020; 129:1373-1382. [PMID: 33031019 DOI: 10.1152/japplphysiol.00296.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We sought to determine how whole body heating acutely influences radial artery function, characterized using flow-mediated dilation (FMD) and low-flow-mediated constriction (L-FMC), and the mechanistic role of shear rate modification on radial artery functional characteristics during heating. Eleven young healthy men underwent whole body heating (water-perfused suit) sufficient to raise the core temperature by +1°C. Trials were repeated with (heat + WC) and without (heat) the application of a wrist cuff located distal to the radial artery examined, known to prevent increases in mean and anterograde shear rates but increase retrograde shear rate. Radial artery characteristics were assessed throughout each trial, with FMD and L-FMC assessed before and upon reaching the target core temperature. Heat markedly increased radial artery mean and anterograde shear rates, along with radial artery diameter and blood flow (P < 0.05). Heat + WC abolished the heat-induced increase in mean and anterograde shear rates (P > 0.05) but markedly increased retrograde shear rate (P < 0.05). Concomitantly, increases in radial artery diameter and blood flow were decreased (heat + WC vs. heat, P < 0.05). Heat attenuated FMD (8.6 ± 1.2% vs. 2.2 ± 1.4%, P < 0.05), whereas no change in FMD was observed in heat + WC (7.8 ± 1.2% vs. 10.8 ± 1.2%, P > 0.05). In contrast, L-FMC was not different in either trial (P > 0.05). In summary, acute whole body heating markedly elevates radial artery shear rate, diameter, and blood flow and diminishes FMD. However, marked radial artery vasodilation and diminished FMD are absent when these shear rate changes are prevented. Shear rate modifications underpin the radial artery response to acute whole body heat stress, but further endothelium-dependent vasodilation (FMD) is attenuated likely as the vasodilatory range limit is approached.NEW & NOTEWORTHY We observed that acute whole body heating elevates radial artery shear rate, diameter, and blood flow. This results in a diminished flow-meditated dilatation (FMD) but does not change low-flow-mediated constriction (L-FMC). Preventing shear rate changes during whole body heating reduces radial artery vasodilation and reverses FMD reductions but has no effect on L-FMC. These findings indicate that shear rate changes underpin conduit artery responses to acute whole body heat stress, but further endothelium-dependent flow-mediated vasodilation is attenuated as the vasodilatory range limit is approached.
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Affiliation(s)
- Mohammad H Alali
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Lauro C Vianna
- NeuroV̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Distrito Federal, Brazil
| | - Rebekah A I Lucas
- School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Rehan T Junejo
- Department of Life Sciences, Manchester Metropolitan University, Manchester, United Kingdom.,Liverpool Centre for Cardiovascular Science, University of Liverpool, Liverpool, United Kingdom
| | - James P Fisher
- Faculty of Medical & Health Sciences, Department of Physiology, University of Auckland, Auckland, New Zealand
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Cui J, Blaha C, Herr MD, Sinoway LI. Lower-limb venous distension reflex and orthostatic tolerance in young healthy humans. Am J Physiol Regul Integr Comp Physiol 2020; 319:R142-R147. [PMID: 32663039 DOI: 10.1152/ajpregu.00269.2019] [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: 11/22/2022]
Abstract
Earlier reports suggest that limb venous distension evokes reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) (i.e., venous distension reflex). Our recent report also shows that suction of arterially occluded limb evokes venous distension reflex. We postulate that the venous distension reflex contributes to autonomic responses to orthostatic stress. In this study, we hypothesized that orthostatic tolerance would be linked to the MSNA response seen with lower limb suction. Fifteen healthy subjects were tested in the supine position. Negative pressure (-100 mmHg) was applied on an arterially occluded lower limb for 2 min. MSNA from the peroneal nerve in the limb not exposed to suction, ECG, and BP (Finometer) was recorded throughout the study. Limb occlusion without suction was used as a control trial. In a separate visit, the individual's orthostatic tolerance was assessed using a graded lower body negative pressure (LBNP) tolerance test. Mean arterial BP and MSNA (18.6 ± 1.9 to 23.6 ± 2.0 bursts/min) significantly (both P < 0.05) increased during limb suction. Orthostatic tolerance index positively correlated (R = 0.636, P = 0.011) with the MSNA response seen with suction during occlusion. Since the venous distension reflex strength correlates with the level of orthostatic tolerance, we speculate that lower-limb venous distension reflex engagement increases the sympathetic responses during orthostatic challenge and serves to maintain BP with postural stress.
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Affiliation(s)
- Jian Cui
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
| | - Cheryl Blaha
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
| | - Michael D Herr
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
| | - Lawrence I Sinoway
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
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Campos MO, Mansur DE, Mattos JD, Paiva ACS, Videira RLR, Macefield VG, da Nóbrega ACL, Fernandes IA. Acid-sensing ion channels blockade attenuates pressor and sympathetic responses to skeletal muscle metaboreflex activation in humans. J Appl Physiol (1985) 2019; 127:1491-1501. [PMID: 31545154 DOI: 10.1152/japplphysiol.00401.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In animals, the blockade of acid-sensing ion channels (ASICs), cation pore-forming membrane proteins located in the free nerve endings of group IV afferent fibers, attenuates increases in arterial pressure (AP) and sympathetic nerve activity (SNA) during muscle contraction. Therefore, ASICs play a role in mediating the metabolic component (skeletal muscle metaboreflex) of the exercise pressor reflex in animal models. Here we tested the hypothesis that ASICs also play a role in evoking the skeletal muscle metaboreflex in humans, quantifying beat-by-beat mean AP (MAP; finger photoplethysmography) and muscle SNA (MSNA; microneurography) in 11 men at rest and during static handgrip exercise (SHG; 35% of the maximal voluntary contraction) and postexercise muscle ischemia (PEMI) before (B) and after (A) local venous infusion of either saline or amiloride (AM), an ASIC antagonist, via the Bier block technique. MAP (BAM +30 ± 6 vs. AAM +25 ± 7 mmHg, P = 0.001) and MSNA (BAM +14 ± 9 vs. AAM +10 ± 6 bursts/min, P = 0.004) responses to SHG were attenuated under ASIC blockade. Amiloride also attenuated the PEMI-induced increases in MAP (BAM +25 ± 6 vs. AAM +16 ± 6 mmHg, P = 0.0001) and MSNA (BAM +16 ± 9 vs. AAM +8 ± 8 bursts/min, P = 0.0001). MAP and MSNA responses to SHG and PEMI were similar before and after saline infusion. We conclude that ASICs play a role in evoking pressor and sympathetic responses to SHG and the isolated activation of the skeletal muscle metaboreflex in humans. NEW & NOTEWORTHY We showed that regional blockade of the acid-sensing ion channels (ASICs), induced by venous infusion of the antagonist amiloride via the Bier block anesthetic technique, attenuated increases in arterial pressure and muscle sympathetic nerve activity during both static handgrip exercise and postexercise muscle ischemia. These findings indicate that ASICs contribute to both pressor and sympathetic responses to the activation of the skeletal muscle metaboreflex in humans.
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Affiliation(s)
- Monique O Campos
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | - Daniel E Mansur
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | - João D Mattos
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | - Adrielle C S Paiva
- Laboratory of Exercise Sciences, Fluminense Federal University, Niterói, Brazil
| | | | - Vaughan G Macefield
- School of Medicine, Western Sydney University, Sydney, Australia.,Baker Heart and Diabetes Institute, Melbourne, Australia
| | | | - Igor A Fernandes
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
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Teixeira AL, Fernandes IA, Vianna LC. GABA A receptors modulate sympathetic vasomotor outflow and the pressor response to skeletal muscle metaboreflex activation in humans. J Physiol 2019; 597:4139-4150. [PMID: 31247674 DOI: 10.1113/jp277929] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 06/24/2019] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The activation of the group III/IV skeletal muscle afferents is one of the principal mediators of cardiovascular responses to exercise; however, the neuronal circuitry mechanisms that are involved during the activation of group III/IV muscle afferents in humans remain unknown. Recently, we showed that GABAergic mechanisms are involved in the cardiac vagal withdrawal during the activation of mechanically sensitive (predominantly mediated by group III fibres) skeletal muscle afferents in humans. In the present study, we found that increases in muscle sympathetic nerve activity and mean blood pressure during isometric handgrip exercise and postexercise ischaemia were significantly greater after the oral administration of diazepam, a benzodiazepine that increases GABAA activity, but not after placebo administration in young healthy subjects. These findings indicate for the first time that GABAA receptors modulate sympathetic vasomotor outflow and the pressor responses to activation of metabolically sensitive (predominantly mediated by group IV fibres) skeletal muscle afferents in humans. ABSTRACT Animal studies have indicated that GABAA receptors are involved in the neuronal circuitry of the group III/IV skeletal muscle afferent activation-induced neurocardiovascular responses to exercise. In the present study, we aimed to determine whether GABAA receptors modulate the neurocardiovascular responses to activation of metabolically sensitive (predominantly mediated by group IV fibres) skeletal muscle afferents in humans. In a randomized, double-blinded, placebo-controlled and cross-over design, 17 healthy subjects (eight women) performed 2 min of ischaemic isometric handgrip exercise at 30% of the maximal voluntary contraction followed by 2 min of postexercise ischaemia (PEI). Muscle sympathetic nerve activity (MSNA), blood pressure (BP) and heart rate (HR) were continuously measured and trials were conducted before and 60 min after the oral administration of either placebo or diazepam (10 mg), a benzodiazepine that enhances GABAA activity. At rest, MSNA was reduced, whereas HR and BP did not change after diazepam administration. During ischaemic isometric handgrip, greater MSNA (pre: ∆13 ± 9 bursts min-1 vs. post: ∆29 ± 15 bursts min-1 , P < 0.001), HR (pre: ∆23 ± 11 beats min-1 vs. post: ∆31 ± 17 beats min-1 , P < 0.01) and mean BP (pre: ∆33 ± 12 mmHg vs. post: ∆37 ± 12 mmHg, P < 0.01) responses were observed after diazepam. During PEI, MSNA and mean BP remained elevated from baseline before diazepam (∆10 ± 8 bursts min-1 and ∆25 ± 14 mmHg, respectively) and these elevations were increased after diazepam (∆17 ± 12 bursts min-1 and ∆28 ± 13 mmHg, respectively) (P ≤ 0.05). Importantly, placebo pill had no effect on neural, cardiac and pressor responses. These findings demonstrate for the first time that GABAA receptors modulate MSNA and the pressor responses to skeletal muscle metaboreflex activation in humans.
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Affiliation(s)
- André L Teixeira
- NeuroV̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, DF, Brazil
| | - Igor A Fernandes
- NeuroV̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, DF, Brazil
| | - Lauro C Vianna
- NeuroV̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, DF, Brazil
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