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Fernandes LG, MĂĽller LO, FeijĂło RA, Blanco PJ. Closed-loop baroreflex model with biophysically detailed afferent pathway. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2024:e3849. [PMID: 39054666 DOI: 10.1002/cnm.3849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2023] [Revised: 05/22/2024] [Accepted: 06/30/2024] [Indexed: 07/27/2024]
Abstract
In this work, we couple a lumped-parameter closed-loop model of the cardiovascular system with a physiologically-detailed mathematical description of the baroreflex afferent pathway. The model features a classical Hodgkin-Huxley current-type model for the baroreflex afferent limb (primary neuron) and for the second-order neuron in the central nervous system. The pulsatile arterial wall distension triggers a frequency-modulated sequence of action potentials at the afferent neuron. This signal is then integrated at the brainstem neuron model. The efferent limb, representing the sympathetic and parasympathetic nervous system, is described as a transfer function acting on heart and blood vessel model parameters in order to control arterial pressure. Three in silico experiments are shown here: a step increase in the aortic pressure to evaluate the functionality of the reflex arch, a hemorrhagic episode and an infusion simulation. Through this model, it is possible to study the biophysical dynamics of the ionic currents proposed for the afferent limb components of the baroreflex during the cardiac cycle, and the way in which currents dynamics affect the cardiovascular function. Moreover, this system can be further developed to study in detail each baroreflex loop component, helping to unveil the mechanisms involved in the cardiovascular afferent information processing.
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Affiliation(s)
- Luciano Gonçalves Fernandes
- Instituto de CiĂŞncias BiolĂłgicas e da SaĂşde, Universidade Federal Rural do Rio de Janeiro, Rio de Janeiro, Brazil
- Instituto Nacional de CiĂŞncia e Tecnologia em Medicina Assistida por Computação CientĂfica, Rio de Janeiro, Brazil
| | - Lucas Omar MĂĽller
- Instituto Nacional de CiĂŞncia e Tecnologia em Medicina Assistida por Computação CientĂfica, Rio de Janeiro, Brazil
- Coordenação de MĂ©todos Matemáticos e Computacionais, LaboratĂłrio Nacional de Computação CientĂfica, PetrĂłpolis, Brazil
- Department of Mathematics, University of Trento, Trento, Italy
| | - RaĂşl Antonino FeijĂło
- Instituto Nacional de CiĂŞncia e Tecnologia em Medicina Assistida por Computação CientĂfica, Rio de Janeiro, Brazil
- Coordenação de MĂ©todos Matemáticos e Computacionais, LaboratĂłrio Nacional de Computação CientĂfica, PetrĂłpolis, Brazil
| | - Pablo Javier Blanco
- Instituto Nacional de CiĂŞncia e Tecnologia em Medicina Assistida por Computação CientĂfica, Rio de Janeiro, Brazil
- Coordenação de MĂ©todos Matemáticos e Computacionais, LaboratĂłrio Nacional de Computação CientĂfica, PetrĂłpolis, Brazil
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Verma N, Mudge JD, Kasole M, Chen RC, Blanz SL, Trevathan JK, Lovett EG, Williams JC, Ludwig KA. Auricular Vagus Neuromodulation-A Systematic Review on Quality of Evidence and Clinical Effects. Front Neurosci 2021; 15:664740. [PMID: 33994937 PMCID: PMC8120162 DOI: 10.3389/fnins.2021.664740] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/25/2021] [Indexed: 12/13/2022] Open
Abstract
Background: The auricular branch of the vagus nerve runs superficially, which makes it a favorable target for non-invasive stimulation techniques to modulate vagal activity. For this reason, there have been many early-stage clinical trials on a diverse range of conditions. These trials often report conflicting results for the same indication. Methods: Using the Cochrane Risk of Bias tool we conducted a systematic review of auricular vagus nerve stimulation (aVNS) randomized controlled trials (RCTs) to identify the factors that led to these conflicting results. The majority of aVNS studies were assessed as having "some" or "high" risk of bias, which makes it difficult to interpret their results in a broader context. Results: There is evidence of a modest decrease in heart rate during higher stimulation dosages, sometimes at above the level of sensory discomfort. Findings on heart rate variability conflict between studies and are hindered by trial design, including inappropriate washout periods, and multiple methods used to quantify heart rate variability. There is early-stage evidence to suggest aVNS may reduce circulating levels and endotoxin-induced levels of inflammatory markers. Studies on epilepsy reached primary endpoints similar to previous RCTs testing implantable vagus nerve stimulation therapy. Preliminary evidence shows that aVNS ameliorated pathological pain but not evoked pain. Discussion: Based on results of the Cochrane analysis we list common improvements for the reporting of results, which can be implemented immediately to improve the quality of evidence. In the long term, existing data from aVNS studies and salient lessons from drug development highlight the need for direct measures of local neural target engagement. Direct measures of neural activity around the electrode will provide data for the optimization of electrode design, placement, and stimulation waveform parameters to improve on-target engagement and minimize off-target activation. Furthermore, direct measures of target engagement, along with consistent evaluation of blinding success, must be used to improve the design of controls-a major source of concern identified in the Cochrane analysis. The need for direct measures of neural target engagement and consistent evaluation of blinding success is applicable to the development of other paresthesia-inducing neuromodulation therapies and their control designs.
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Affiliation(s)
- Nishant Verma
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
| | - Jonah D. Mudge
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
| | - MaĂŻsha Kasole
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
| | - Rex C. Chen
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
| | - Stephan L. Blanz
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
| | - James K. Trevathan
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
| | | | - Justin C. Williams
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
- Department of Neurosurgery, University of Wisconsin – Madison, Madison, WI, United States
| | - Kip A. Ludwig
- Department of Biomedical Engineering, University of Wisconsin – Madison, Madison, WI, United States
- Wisconsin Institute for Translational Neuroengineering (WITNe) – Madison, Madison, WI, United States
- Department of Neurosurgery, University of Wisconsin – Madison, Madison, WI, United States
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Nicolai EN, Settell ML, Knudsen BE, McConico AL, Gosink BA, Trevathan JK, Baumgart IW, Ross EK, Pelot NA, Grill WM, Gustafson KJ, Shoffstall AJ, Williams JC, Ludwig KA. Sources of off-target effects of vagus nerve stimulation using the helical clinical lead in domestic pigs. J Neural Eng 2020; 17:046017. [PMID: 32554888 PMCID: PMC7717671 DOI: 10.1088/1741-2552/ab9db8] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Objective Clinical data suggest that efficacious vagus nerve stimulation (VNS) is limited by side effects such as cough and dyspnea that have stimulation thresholds lower than those for therapeutic outcomes. VNS side effects are putatively caused by activation of nearby muscles within the neck, via direct muscle activation or activation of nerve fibers innervating those muscles. Our goal was to determine the thresholds at which various VNS-evoked effects occur in the domestic pig—an animal model with vagus anatomy similar to human—using the bipolar helical lead deployed clinically. Approach Intrafascicular electrodes were placed within the vagus nerve to record electroneurographic (ENG) responses, and needle electrodes were placed in the vagal-innervated neck muscles to record electromyographic (EMG) responses. Main results Contraction of the cricoarytenoid muscle occurred at low amplitudes (~0.3 mA) and resulted from activation of motor nerve fibers in the cervical vagus trunk within the electrode cuff which bifurcate into the recurrent laryngeal branch of the vagus. At higher amplitudes (~1.4 mA), contraction of the cricoarytenoid and cricothyroid muscles was generated by current leakage outside the cuff to activate motor nerve fibers running within the nearby superior laryngeal branch of the vagus. Activation of these muscles generated artifacts in the ENG recordings that may be mistaken for compound action potentials representing slowly conducting Aδ-, B-, and C-fibers. Significance Our data resolve conflicting reports of the stimulation amplitudes required for C-fiber activation in large animal studies (>10 mA) and human studies (<250 μA). After removing muscle-generated artifacts, ENG signals with post-stimulus latencies consistent with Aδ- and B-fibers occurred in only a small subset of animals, and these signals had similar thresholds to those that caused bradycardia. By identifying specific neuroanatomical pathways that cause off-target effects and characterizing the stimulation dose-response curves for on- and off-target effects, we hope to guide interpretation and optimization of clinical VNS.
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Affiliation(s)
- Evan N Nicolai
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Megan L Settell
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Bruce E Knudsen
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, Mayo Clinic, Rochester, MN, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Andrea L McConico
- Department of Neurosurgery, Mayo Clinic, Rochester, MN, United States of America
| | - Brian A Gosink
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, United States of America
| | - James K Trevathan
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Ian W Baumgart
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
| | - Erika K Ross
- Abbott Neuromodulation, Plano, TX, United States of America
| | - Nicole A Pelot
- Department of Biomedical Engineering, Duke University, Durham, NC, United States of America
| | - Warren M Grill
- Department of Biomedical Engineering, Duke University, Durham, NC, United States of America
| | - Kenneth J Gustafson
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States of America
- Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States of America
| | - Andrew J Shoffstall
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States of America
- Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States of America
| | - Justin C Williams
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
| | - Kip A Ludwig
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States of America
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, United States of America
- Wisconsin Institute of Neuroengineering (WITNe), University of Wisconsin-Madison, WI, United States of America
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Effects of a TRPV1 agonist capsaicin on respiratory rhythm generation in brainstem-spinal cord preparation from newborn rats. Pflugers Arch 2016; 469:327-338. [PMID: 27900462 DOI: 10.1007/s00424-016-1912-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 11/20/2016] [Accepted: 11/22/2016] [Indexed: 12/19/2022]
Abstract
The heat-sensitive transient receptor potential vanilloid 1 (TRPV1) channels are expressed in the peripheral and central nervous systems. However, there is no report on how the activation of TRPV1 causes the modulation of neuronal activity in the medullary respiratory center. We examined effects of capsaicin, a specific agonist of TRPV1 channels, on respiratory rhythm generation in brainstem-spinal cord preparation from newborn rats. Capsaicin induced a biphasic response in the respiratory rhythm (a transient decrease followed by an increase in the C4 rate). The second-phase excitatory effect (but not the initial inhibitory effect) in the biphasic response was partly blocked by capsazepine or AMG9810 (TRPV1 antagonists). Capsaicin caused strong desensitization. After its washout, the strength of C4 burst inspiratory activity was augmented once per four to five respiratory cycles. The preinspiratory and inspiratory neurons showed tonic firings due to membrane depolarization during the initial inhibitory phase. In the presence of TTX, capsaicin increased the fluctuation of the membrane potential of the CO2-sensitive preinspiratory neurons in the parafacial respiratory group (pFRG), accompanied by slight depolarization. The C4 inspiratory activity did not stop, even 60-90Â min after the application of 50/100Â ÎĽM capsaicin. Voltage-sensitive dye imaging demonstrated that the spatiotemporal pattern of the respiratory rhythm generating networks after application of capsaicin (50Â ÎĽM, 70-90Â min) was highly similar to the control. A histochemical analysis using TRPV1 channel protein antibodies and mRNA demonstrated that the TRPV1 channel-positive cells were widely distributed in the reticular formation of the medulla, including the pFRG. Our results showed that the application of capsaicin in the medulla has various influences on the respiratory center: transient inhibitory and subsequent excitatory effects on the respiratory rhythm and periodical augmentation of the inspiratory burst pattern. The effects of capsaicin were partially blocked by TRPV1 antagonists but could be also induced at least partially via the non-specific action. Our results also suggested a minor contribution of the TRPV1 channels to central chemoreception.
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Lee CK, Park KH, Baik SK, Jeong SW. Decreased excitability and voltage-gated sodium currents in aortic baroreceptor neurons contribute to the impairment of arterial baroreflex in cirrhotic rats. Am J Physiol Regul Integr Comp Physiol 2016; 310:R1088-101. [DOI: 10.1152/ajpregu.00129.2015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 03/10/2016] [Indexed: 02/07/2023]
Abstract
Cardiovascular autonomic dysfunction, which is manifested by an impairment of the arterial baroreflex, is prevalent irrespective of etiology and contributes to the increased morbidity and mortality in cirrhotic patients. However, the cellular mechanisms that underlie the cirrhosis-impaired arterial baroreflex remain unknown. In the present study, we examined whether the cirrhosis-impaired arterial baroreflex is attributable to the dysfunction of aortic baroreceptor (AB) neurons. Biliary and nonbiliary cirrhotic rats were generated via common bile duct ligation (CBDL) and intraperitoneal injections of thioacetamide (TAA), respectively. Histological and molecular biological examinations confirmed the development of fibrosis in the livers of both cirrhotic rat models. The heart rate changes during phenylephrine-induced baroreceptor activation indicated that baroreflex sensitivity was blunted in the CBDL and TAA rats. Under the current-clamp mode of the patch-clamp technique, cell excitability was recorded in DiI-labeled AB neurons. The number of action potential discharges in the A- and C-type AB neurons was significantly decreased because of the increased rheobase and threshold potential in the CBDL and TAA rats compared with sham-operated rats. Real-time PCR and Western blotting indicated that the NaV1.7, NaV1.8, and NaV1.9 transcripts and proteins were significantly downregulated in the nodose ganglion neurons from the CBDL and TAA rats compared with the sham-operated rats. Consistent with these molecular data, the tetrodotoxin-sensitive NaV currents and the tetrodotoxin-resistant NaV currents were significantly decreased in A- and C-type AB neurons, respectively, from the CBDL and TAA rats compared with the sham-operated rats. Taken together, these findings implicate a key cellular mechanism in the cirrhosis-impaired arterial baroreflex.
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Affiliation(s)
- Choong-Ku Lee
- Department of Physiology, Brain Research Group, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Kwang-Hwa Park
- Department of Pathology, Brain Research Group, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Soon-Koo Baik
- Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
| | - Seong-Woo Jeong
- Department of Physiology, Brain Research Group, Yonsei University Wonju College of Medicine, Wonju, Republic of Korea
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Turner MJ, Kawada T, Shimizu S, Fukumitsu M, Sugimachi M. Differences in the dynamic baroreflex characteristics of unmyelinated and myelinated central pathways are less evident in spontaneously hypertensive rats. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1397-405. [DOI: 10.1152/ajpregu.00315.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 09/09/2015] [Indexed: 11/22/2022]
Abstract
The aim of the study was to identify the contribution of myelinated (A-fiber) and unmyelinated (C-fiber) baroreceptor central pathways to the baroreflex control of sympathetic nerve activity (SNA) and arterial pressure (AP) in anesthetized Wistar-Kyoto (WKY; n = 8) and spontaneously hypertensive rats (SHR; n = 8). The left aortic depressor nerve (ADN) was electrically stimulated with two types of binary white noise signals designed to preferentially activate A-fibers (A-BRx protocol) or C-fibers (C-BRx protocol). In WKY, the central arc transfer function from ADN stimulation to SNA estimated by A-BRx showed strong derivative characteristics with the slope of dynamic gain between 0.1 and 1 Hz ( Gslope) of 14.63 ± 0.89 dB/decade. In contrast, the central arc transfer function estimated by C-BRx exhibited nonderivative characteristics with Gslope of 0.64 ± 1.13 dB/decade. This indicates that A-fibers are important for rapid baroreflex regulation, whereas C-fibers are likely important for more sustained regulation of SNA and AP. In SHR, the central arc transfer function estimated by A-BRx showed higher Gslope (18.46 ± 0.75 dB/decade, P < 0.01) and that estimated by C-BRx showed higher Gslope (8.62 ± 0.64 dB/decade, P < 0.001) with significantly lower dynamic gain at 0.01 Hz (6.29 ± 0.48 vs. 2.80 ± 0.36%/Hz, P < 0.001) compared with WKY. In conclusion, the dynamic characteristics of the A-fiber central pathway are enhanced in the high-modulation frequency range (0.1–1 Hz) and those of the C-fiber central pathway are attenuated in the low-modulation frequency range (0.01–0.1 Hz) in SHR.
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Affiliation(s)
- Michael J. Turner
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan; and
| | - Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan; and
| | - Shuji Shimizu
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan; and
| | - Masafumi Fukumitsu
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan; and
- Department of Artificial Organ Medicine, Faculty of Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Masaru Sugimachi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan; and
- Department of Artificial Organ Medicine, Faculty of Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
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Hofmann ME, Andresen MC. Vanilloids selectively sensitize thermal glutamate release from TRPV1 expressing solitary tract afferents. Neuropharmacology 2015; 101:401-11. [PMID: 26471418 DOI: 10.1016/j.neuropharm.2015.10.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 09/11/2015] [Accepted: 10/07/2015] [Indexed: 01/09/2023]
Abstract
Vanilloids, high temperature, and low pH activate the transient receptor potential vanilloid type 1 (TRPV1) receptor. In spinal dorsal root ganglia, co-activation of one of these gating sites on TRPV1 sensitized receptor gating by other modes. Here in rat brainstem slices, we examined glutamate synaptic transmission in nucleus of the solitary tract (NTS) neurons where most cranial primary afferents express TRPV1, but TRPV1 sensitization is unknown. Electrical shocks to the solitary tract (ST) evoked EPSCs (ST-EPSCs). Activation of TRPV1 with capsaicin (100 nM) increased spontaneous EPSCs (sEPSCs) but inhibited ST-EPSCs. High concentrations of the ultra-potent vanilloid resiniferatoxin (RTX, 1 nM) similarly increased sEPSC rates but blocked ST-EPSCs. Lowering the RTX concentration to 150 pM modestly increased the frequency of the sEPSCs without causing failures in the evoked ST-EPSCs. The sEPSC rate increased with raising bath temperature to 36 °C. Such thermal responses were larger in 150 pM RTX, while the ST-EPSCs remained unaffected. Vanilloid sensitization of thermal responses persisted in TTX but was blocked by the TRPV1 antagonist capsazepine. Our results demonstrate that multimodal activation of TRPV1 facilitates sEPSC responses in more than the arithmetic sum of the two activators, i.e. co-activation sensitizes TRPV1 control of spontaneous glutamate release. Since action potential evoked glutamate release is unaltered, the work provides evidence for cooperativity in gating TRPV1 plus a remarkable separation of calcium mechanisms governing the independent vesicle pools responsible for spontaneous and evoked release at primary afferents in the NTS.
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Affiliation(s)
- Mackenzie E Hofmann
- Department of Physiology & Pharmacology, Oregon Health & Science University, Portland, OR, USA.
| | - Michael C Andresen
- Department of Physiology & Pharmacology, Oregon Health & Science University, Portland, OR, USA
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Turner MJ, Kawada T, Shimizu S, Fukumitsu M, Sugimachi M. Open-loop characteristics of the arterial baroreflex after blockade of unmyelinated baroreceptors with resiniferatoxin. Auton Neurosci 2015; 193:38-43. [PMID: 26049262 DOI: 10.1016/j.autneu.2015.05.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 05/25/2015] [Accepted: 05/26/2015] [Indexed: 02/01/2023]
Abstract
Arterial baroreceptors can be divided into two categories dependent on whether their axons are myelinated (A-fiber) or unmyelinated (C-fiber). We investigated the effect of periaxonal resiniferatoxin (RTX), a blocker of C-fiber baroreceptor activity, on the open-loop static characteristics of the arterial baroreflex. The baroreceptor region of the right aortic depressor nerve was isolated, and intra-baroreceptor region pressure (BRP) was changed from 60 to 180 mm Hg in 10 anesthetized Sprague-Dawley rats. Open-loop static characteristics of the neural arc from BRP to efferent sympathetic nerve activity (SNA), peripheral arc from SNA to arterial pressure (AP), and total reflex arc from BRP to AP were estimated. Although blocking C-fiber activity with RTX resulted in a lower response range (33.7±4.6% and 49.4±4.8%, P<0.01) and higher minimum SNA (78.0±4.7% and 53.6±5.0%, P<0.001) of the steady-state neural arc, the peak SNA response to BRP was greater at a BRP of 160 mm Hg (-37.87±5.83% and -26.28±4.90%, P=0.01). RTX also resulted in a lower response range (27.8±5.0 mm Hg and 40.9±5.2 mm Hg, P<0.01) and higher minimum AP (92.4±4.7 mm Hg and 79.1±4.9 mm Hg, P<0.001) of the total reflex arc. Despite these changes, the maximum slope of the neural arc and the maximum gain of the total reflex arc did not differ significantly after RTX. These data suggest that A-fiber baroreceptors can regulate AP and maintain the maximum gain when systemic AP is around the normal operating range. In contrast, C-fiber baroreceptors are critically important for reductions in SNA and AP when systemic AP is raised above the normal operating range.
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Affiliation(s)
- Michael J Turner
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan.
| | - Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan
| | - Shuji Shimizu
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan
| | - Masafumi Fukumitsu
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan; Department of Artificial Organ Medicine, Faculty of Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Masaru Sugimachi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka 565-8565, Japan; Department of Artificial Organ Medicine, Faculty of Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
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Santa Cruz Chavez GC, Li BY, Glazebrook PA, Kunze DL, Schild JH. An afferent explanation for sexual dimorphism in the aortic baroreflex of rat. Am J Physiol Heart Circ Physiol 2014; 307:H910-21. [PMID: 25038145 DOI: 10.1152/ajpheart.00332.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sex differences in baroreflex (BRx) function are well documented. Hormones likely contribute to this dimorphism, but many functional aspects remain unresolved. Our lab has been investigating a subset of vagal sensory neurons that constitute nearly 50% of the total population of myelinated aortic baroreceptors (BR) in female rats but less than 2% in male rats. Termed "Ah," this unique phenotype has many of the nonoverlapping electrophysiological properties and chemical sensitivities of both myelinated A-type and unmyelinated C-type BR afferents. In this study, we utilize three distinct experimental protocols to determine if Ah-type barosensory afferents underlie, at least in part, the sex-related differences in BRx function. Electron microscopy of the aortic depressor nerve (ADN) revealed that female rats have less myelin (P < 0.03) and a smaller fiber cross-sectional area (P < 0.05) per BR fiber than male rats. Electrical stimulation of the ADN evoked compound action potentials and nerve conduction profiles that were markedly different (P < 0.01, n = 7 females and n = 9 males). Selective activation of ADN myelinated fibers evoked a BRx-mediated depressor response that was 3-7 times greater in female (n = 16) than in male (n = 17) rats. Interestingly, the most striking hemodynamic difference was functionally dependent upon the rate of myelinated barosensory fiber activation. Only 5-10 Hz of stimulation evoked a rapid, 20- to 30-mmHg reduction in arterial pressure of female rats, whereas rates of 50 Hz or higher were required to elicit a comparable depressor response from male rats. Collectively, our experimental results are suggestive of an alternative myelinated baroreceptor afferent pathway in females that may account for, at least in part, the noted sex-related differences in autonomic control of cardiovascular function.
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Affiliation(s)
- Grace C Santa Cruz Chavez
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana; Department of Biomedical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, Indiana
| | - Bai-Yan Li
- Department of Biomedical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, Indiana
| | - Patricia A Glazebrook
- Rammelkamp Center for Education and Research, MetroHealth Campus, Cleveland, Ohio; and
| | - Diana L Kunze
- Rammelkamp Center for Education and Research, MetroHealth Campus, Cleveland, Ohio; and Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio
| | - John H Schild
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana; Department of Biomedical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, Indiana;
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Turner MJ, Kawada T, Shimizu S, Sugimachi M. Sustained reduction in blood pressure from electrical activation of the baroreflex is mediated via the central pathway of unmyelinated baroreceptors. Life Sci 2014; 106:40-9. [PMID: 24780319 DOI: 10.1016/j.lfs.2014.04.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 03/27/2014] [Accepted: 04/17/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Michael J Turner
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan.
| | - Toru Kawada
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Shuji Shimizu
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Masaru Sugimachi
- Department of Cardiovascular Dynamics, National Cerebral and Cardiovascular Center, Osaka, Japan
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Cao Z, Balasubramanian A, Marrelli SP. Pharmacologically induced hypothermia via TRPV1 channel agonism provides neuroprotection following ischemic stroke when initiated 90 min after reperfusion. Am J Physiol Regul Integr Comp Physiol 2013; 306:R149-56. [PMID: 24305062 DOI: 10.1152/ajpregu.00329.2013] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Traditional methods of therapeutic hypothermia show promise for neuroprotection against cerebral ischemia-reperfusion (I/R), however, with limitations. We examined effectiveness and specificity of pharmacological hypothermia (PH) by transient receptor potential vanilloid 1 (TRPV1) channel agonism in the treatment of focal cerebral I/R. Core temperature (T(core)) was measured after subcutaneous infusion of TRPV1 agonist dihydrocapsaicin (DHC) in conscious C57BL/6 WT and TRPV1 knockout (KO) mice. Acute measurements of heart rate (HR), mean arterial pressure (MAP), and cerebral perfusion were measured before and after DHC treatment. Focal cerebral I/R (1 h ischemia + 24 h reperfusion) was induced by distal middle cerebral artery occlusion. Hypothermia (>8 h) was initiated 90 min after start of reperfusion by DHC infusion (osmotic pump). Neurofunction (behavioral testing) and infarct volume (TTC staining) were measured at 24 h. DHC (1.25 mg/kg) produced a stable drop in T(core) (33°C) in naive and I/R mouse models but not in TRPV1 KO mice. DHC (1.25 mg/kg) had no measurable effect on HR and cerebral perfusion but produced a slight transient drop in MAP (<6 mmHg). In stroke mice, DHC infusion produced hypothermia, decreased infarct volume by 87%, and improved neurofunctional score. The hypothermic and neuroprotective effects of DHC were absent in TRPV1 KO mice or mice maintained normothermic with heat support. PH via TRPV1 agonist appears to be a well-tolerated and effective method for promoting mild hypothermia in the conscious mouse. Furthermore, TRPV1 agonism produces effective hypothermia in I/R mice and significantly improves outcome when initiated 90 min after start of reperfusion.
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Affiliation(s)
- Zhijuan Cao
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas
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Martin JL, Jenkins VK, Hsieh HY, Balkowiec A. Brain-derived neurotrophic factor in arterial baroreceptor pathways: implications for activity-dependent plasticity at baroafferent synapses. J Neurochem 2008; 108:450-64. [PMID: 19054281 DOI: 10.1111/j.1471-4159.2008.05781.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Functional characteristics of the arterial baroreceptor reflex change throughout ontogenesis, including perinatal adjustments of the reflex gain and adult resetting during hypertension. However, the cellular mechanisms that underlie these functional changes are not completely understood. Here, we provide evidence that brain-derived neurotrophic factor (BDNF), a neurotrophin with a well-established role in activity-dependent neuronal plasticity, is abundantly expressed in vivo by a large subset of developing and adult rat baroreceptor afferents. Immunoreactivity to BDNF is present in the cell bodies of baroafferent neurons in the nodose ganglion, their central projections in the solitary tract, and terminal-like structures in the lower brainstem nucleus tractus solitarius. Using ELISA in situ combined with electrical field stimulation, we show that native BDNF is released from cultured newborn nodose ganglion neurons in response to patterns that mimic the in vivo activity of baroreceptor afferents. In particular, high-frequency bursting patterns of baroreceptor firing, which are known to evoke plastic changes at baroreceptor synapses, are significantly more effective at releasing BDNF than tonic patterns of the same average frequency. Together, our study indicates that BDNF expressed by first-order baroreceptor neurons is a likely mediator of both developmental and post-developmental modifications at first-order synapses in arterial baroreceptor pathways.
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Affiliation(s)
- Jessica L Martin
- Department of Integrative Biosciences, Oregon Health and Science University, Portland, OR 97239, USA
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Andresen MC, Peters JH. Comparison of baroreceptive to other afferent synaptic transmission to the medial solitary tract nucleus. Am J Physiol Heart Circ Physiol 2008; 295:H2032-42. [PMID: 18790834 DOI: 10.1152/ajpheart.00568.2008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cranial nerve visceral afferents enter the brain stem to synapse on neurons within the solitary tract nucleus (NTS). The broad heterogeneity of both visceral afferents and NTS neurons makes understanding afferent synaptic transmission particularly challenging. To study a specific subgroup of second-order neurons in medial NTS, we anterogradely labeled arterial baroreceptor afferents of the aortic depressor nerve (ADN) with lipophilic fluorescent tracer (i.e., ADN+) and measured synaptic responses to solitary tract (ST) activation recorded from dye-identified neurons in medial NTS in horizontal brain stem slices. Every ADN+ NTS neuron received constant-latency ST-evoked excitatory postsynaptic currents (EPSCs) (jitter < 192 micros, SD of latency). Stimulus-recruitment profiles showed single thresholds and no suprathreshold recruitment, findings consistent with EPSCs arising from a single, branched afferent axon. Frequency-dependent depression of ADN+ EPSCs averaged approximately 70% for five shocks at 50 Hz, but single-shock failure rates did not exceed 4%. Whether adjacent ADN- or those from unlabeled animals, other second-order NTS neurons (jitters < 200 micros) had ST transmission properties indistinguishable from ADN+. Capsaicin (CAP; 100 nM) blocked ST transmission in some neurons. CAP-sensitive ST-EPSCs were smaller and failed over five times more frequently than CAP-resistant responses, whether ADN+ or from unlabeled animals. Variance-mean analysis of ST-EPSCs suggested uniformly high probabilities for quantal glutamate release across second-order neurons. While amplitude differences may reflect different numbers of contacts, higher frequency-dependent failure rates in CAP-sensitive ST-EPSCs may arise from subtype-specific differences in afferent axon properties. Thus afferent transmission within medial NTS differed by axon class (e.g., CAP sensitive) but was indistinguishable by source of axon (e.g., baroreceptor vs. nonbaroreceptor).
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Affiliation(s)
- Michael C Andresen
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon 97239-3098, USA.
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Andresen MC, Bailey TW, Jin YH, McDougall SJ, Peters JH, Aicher SA. Cellular Heterogeneity Within the Solitary Tract Nucleus and Visceral Afferent Processing—Electrophysiological Approaches to Discerning Pathway Performance. Tzu Chi Med J 2007. [DOI: 10.1016/s1016-3190(10)60014-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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15
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Intrathecal administration of resiniferatoxin produces analgesia against prostatodynia in rats. Chin Med J (Engl) 2007. [DOI: 10.1097/00029330-200709020-00013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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