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Thio BJ, Titus ND, Pelot NA, Grill WM. Reverse-engineered models reveal differential membrane properties of autonomic and cutaneous unmyelinated fibers. PLoS Comput Biol 2024; 20:e1012475. [PMID: 39374306 DOI: 10.1371/journal.pcbi.1012475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 10/17/2024] [Accepted: 09/11/2024] [Indexed: 10/09/2024] Open
Abstract
Unmyelinated C-fibers constitute the vast majority of axons in peripheral nerves and play key roles in homeostasis and signaling pain. However, little is known about their ion channel expression, which controls their firing properties. Also, because of their small diameters (~ 1 μm), it has not been possible to characterize their membrane properties using voltage clamp. We developed a novel library of isoform-specific ion channel models to serve as the basis functions of our C-fiber models. We then developed a particle swarm optimization (PSO) framework that used the isoform-specific ion channel models to reverse engineer C-fiber membrane properties from measured autonomic and cutaneous C-fiber conduction responses. Our C-fiber models reproduced experimental conduction velocity, chronaxie, action potential duration, intracellular threshold, and paired pulse recovery cycle. The models also matched experimental activity-dependent slowing, a property not included in model optimization. We found that simple conduction responses, characterizing the action potential, were controlled by similar membrane properties in both the autonomic and cutaneous C-fiber models, but complicated conduction response, characterizing the afterpotenials, were controlled by differential membrane properties. The unmyelinated C-fiber models constitute important tools to study autonomic signaling, assess the mechanisms of pain, and design bioelectronic devices. Additionally, the novel reverse engineering approach can be applied to generate models of other neurons where voltage clamp data are not available.
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Affiliation(s)
- Brandon J Thio
- Department of Biomedical Engineering Duke University Durham, North Carolina, United States of America
| | - Nathan D Titus
- Department of Biomedical Engineering Duke University Durham, North Carolina, United States of America
| | - Nicole A Pelot
- Department of Biomedical Engineering Duke University Durham, North Carolina, United States of America
| | - Warren M Grill
- Department of Biomedical Engineering Duke University Durham, North Carolina, United States of America
- Duke University, Department of Electrical and Computer Engineering, Durham, North Carolina, United States of America
- Duke University School of Medicine, Department of Neurobiology, Durham, North Carolina, United States of America
- Duke University School of Medicine, Department of Neurosurgery, Durham, North Carolina, United States of America
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2
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Musselman ED, Pelot NA, Grill WM. Validated computational models predict vagus nerve stimulation thresholds in preclinical animals and humans. J Neural Eng 2023; 20:10.1088/1741-2552/acda64. [PMID: 37257454 PMCID: PMC10324064 DOI: 10.1088/1741-2552/acda64] [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: 01/30/2023] [Accepted: 05/31/2023] [Indexed: 06/02/2023]
Abstract
Objective.We demonstrated how automated simulations to characterize electrical nerve thresholds, a recently published open-source software for modeling stimulation of peripheral nerves, can be applied to simulate accurately nerve responses to electrical stimulation.Approach.We simulated vagus nerve stimulation (VNS) for humans, pigs, and rats. We informed our models using histology from sample-specific or representative nerves, device design features (i.e. cuff, waveform), published material and tissue conductivities, and realistic fiber models.Main results.Despite large differences in nerve size, cuff geometry, and stimulation waveform, the models predicted accurate activation thresholds across species and myelinated fiber types. However, our C fiber model thresholds overestimated thresholds across pulse widths, suggesting that improved models of unmyelinated nerve fibers are needed. Our models of human VNS yielded accurate thresholds to activate laryngeal motor fibers and captured the inter-individual variability for both acute and chronic implants. For B fibers, our small-diameter fiber model underestimated threshold and saturation for pulse widths >0.25 ms. Our models of pig VNS consistently captured the range ofin vivothresholds across all measured nerve and physiological responses (i.e. heart rate, Aδ/B fibers, Aγfibers, electromyography, and Aαfibers). In rats, our smallest diameter myelinated fibers accurately predicted fast fiber thresholds across short and intermediate pulse widths; slow unmyelinated fiber thresholds overestimated thresholds across shorter pulse widths, but there was overlap for pulse widths >0.3 ms.Significance.We elevated standards for models of peripheral nerve stimulation in populations of models across species, which enabled us to model accurately nerve responses, demonstrate that individual-specific differences in nerve morphology produce variability in neural and physiological responses, and predict mechanisms of VNS therapeutic and side effects.
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Affiliation(s)
- Eric D Musselman
- Department of Biomedical Engineering, Duke University, Durham, NC, 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
- Department of Electrical and Computer Engineering, Duke University, Durham, NC, United States of America
- Department of Neurobiology, Duke University, Durham, NC, United States of America
- Department of Neurosurgery, Duke University, Durham, NC, United States of America
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Huffman WJ, Musselman ED, Pelot NA, Grill WM. Measuring and modeling the effects of vagus nerve stimulation on heart rate and laryngeal muscles. Bioelectron Med 2023; 9:3. [PMID: 36797733 PMCID: PMC9936668 DOI: 10.1186/s42234-023-00107-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 02/08/2023] [Indexed: 02/18/2023] Open
Abstract
BACKGROUND Reduced heart rate (HR) during vagus nerve stimulation (VNS) is associated with therapy for heart failure, but stimulation frequency and amplitude are limited by patient tolerance. An understanding of physiological responses to parameter adjustments would allow differential control of therapeutic and side effects. To investigate selective modulation of the physiological responses to VNS, we quantified the effects and interactions of parameter selection on two physiological outcomes: one related to therapy (reduced HR) and one related to side effects (laryngeal muscle EMG). METHODS We applied a broad range of stimulation parameters (mean pulse rates (MPR), intra-burst frequencies, and amplitudes) to the vagus nerve of anesthetized mice. We leveraged the in vivo recordings to parameterize and validate computational models of HR and laryngeal muscle activity across amplitudes and temporal patterns of VNS. We constructed a finite element model of excitation of fibers within the mouse cervical vagus nerve. RESULTS HR decreased with increased amplitude, increased MPR, and decreased intra-burst frequency. EMG increased with increased MPR. Preferential HR effects over laryngeal EMG effects required combined adjustments of amplitude and MPR. The model of HR responses highlighted contributions of ganglionic filtering to VNS-evoked changes in HR at high stimulation frequencies. Overlap in activation thresholds between small and large modeled fibers was consistent with the overlap in dynamic ranges of related physiological measures (HR and EMG). CONCLUSION The present study provides insights into physiological responses to VNS required for informed parameter adjustment to modulate selectively therapeutic effects and side effects.
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Affiliation(s)
- William J. Huffman
- Department of Biomedical Engineering, Duke University, Fitzpatrick CIEMAS, Box 90281, Room 1427, 101 Science Drive, Durham, NC 27708-0281 USA
| | - Eric D. Musselman
- Department of Biomedical Engineering, Duke University, Fitzpatrick CIEMAS, Box 90281, Room 1427, 101 Science Drive, Durham, NC 27708-0281 USA
| | - Nicole A. Pelot
- Department of Biomedical Engineering, Duke University, Fitzpatrick CIEMAS, Box 90281, Room 1427, 101 Science Drive, Durham, NC 27708-0281 USA
| | - Warren M. Grill
- Department of Biomedical Engineering, Duke University, Fitzpatrick CIEMAS, Box 90281, Room 1427, 101 Science Drive, Durham, NC 27708-0281 USA
- Department of Electrical and Computer Engineering, Duke University, Durham, USA
- Department of Neurobiology Engineering, Duke University, Durham, USA
- Department of Neurosurgery Engineering, Duke University, Durham, USA
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Yount M, Peruri A, Morgan A, Zahed M, Fritz V, Simmons Z, Millard J, Redden DT, Reina MA, Roballo KCS. Morphology and morphometry of the human obturator nerve in males and females. Anat Histol Embryol 2023; 52:490-499. [PMID: 36692228 DOI: 10.1111/ahe.12905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 01/09/2023] [Accepted: 01/10/2023] [Indexed: 01/25/2023]
Abstract
Peripheral nerve injury and the nerves' subsequent repair and regeneration continues to be marked clinically by poor functional recovery. The analysis of nerve morphology is an aspect which may provide an impact on successful clinical outcomes through better prediction of donor and recipient matching. In this study, we evaluated the morphological aspects of the human obturator nerve for a better understanding of its potential in nerve transplantation. Morphological characteristics of donor obturator nerves were analysed, including nerve diameter and length, fascicle count and the ratio of neural to non-neural tissue present within the cross-sectional area of the nerve's epineurium, with respect to laterality and sex. Statistical significance (p < 0.10) was determined for male obturator nerves having an average diameter of 2.67 mm compared to female obturator nerves at 1.91 mm, as well as left obturator nerves having an average of 11.21 fascicles compared to the right having an average of 10.17 fascicles. Strong positive correlations were determined between cross-sectional nerve area and limb size index, as well as between percentage of non-neural tissue and area of non-neural tissue, among males. Separately, strong correlation between percentage of non-neural tissue and area of non-neural tissue among right obturator nerves in males and females was determined . These findings indicate that there are associations and predictions that can be made about nerve morphology and that these when combined with other patient characteristics may enhance patient functional recovery following a peripheral nerve's repair.
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Affiliation(s)
- Mason Yount
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - Alekhya Peruri
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - Alexandra Morgan
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - Malek Zahed
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - Virginia Fritz
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - Zachary Simmons
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - Jonathan Millard
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - David T Redden
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA
| | - Miguel Angel Reina
- CEU-San-Pablo University School of Medicine, Madrid, Spain.,Department of Anesthesiology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Kelly C S Roballo
- Edward Via College of Osteopathic Medicine, Blacksburg, Virginia, USA.,Virginia Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, USA
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Jeong H, Cho A, Ay I, Bonmassar G. Short-pulsed micro-magnetic stimulation of the vagus nerve. Front Physiol 2022; 13:938101. [PMID: 36277182 PMCID: PMC9585240 DOI: 10.3389/fphys.2022.938101] [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: 05/06/2022] [Accepted: 09/01/2022] [Indexed: 11/30/2022] Open
Abstract
Vagus nerve stimulation (VNS) is commonly used to treat drug-resistant epilepsy and depression. The therapeutic effect of VNS depends on stimulating the afferent vagal fibers. However, the vagus is a mixed nerve containing afferent and efferent fibers, and the stimulation of cardiac efferent fibers during VNS may produce a rare but severe risk of bradyarrhythmia. This side effect is challenging to mitigate since VNS, via electrical stimulation technology used in clinical practice, requires unique electrode design and pulse optimization for selective stimulation of only the afferent fibers. Here we describe a method of VNS using micro-magnetic stimulation (µMS), which may be an alternative technique to induce a focal stimulation, enabling a selective fiber stimulation. Micro-coils were implanted into the cervical vagus nerve in adult male Wistar rats. For comparison, the physiological responses were recorded continuously before, during, and after stimulation with arterial blood pressure (ABP), respiration rate (RR), and heart rate (HR). The electrical VNS caused a decrease in ABP, RR, and HR, whereas µM-VNS only caused a transient reduction in RR. The absence of an HR modulation indicated that µM-VNS might provide an alternative technology to VNS with fewer heart-related side effects, such as bradyarrhythmia. Numerical electromagnetic simulations helped estimate the optimal coil orientation with respect to the nerve to provide information on the electric field’s spatial distribution and strength. Furthermore, a transmission emission microscope provided very high-resolution images of the cervical vagus nerve in rats, which identified two different populations of nerve fibers categorized as large and small myelinated fibers.
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Affiliation(s)
- Hongbae Jeong
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
| | - Annabel Cho
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
- Department of Bioengineering, Harvard University, Cambridge, MA, United States
| | - Ilknur Ay
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
| | - Giorgio Bonmassar
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States
- *Correspondence: Giorgio Bonmassar,
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Yokota H, Edama M, Hirabayashi R, Sekine C, Otsuru N, Saito K, Kojima S, Miyaguchi S, Onishi H. Effects of Stimulus Frequency, Intensity, and Sex on the Autonomic Response to Transcutaneous Vagus Nerve Stimulation. Brain Sci 2022; 12:brainsci12081038. [PMID: 36009101 PMCID: PMC9405815 DOI: 10.3390/brainsci12081038] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 07/29/2022] [Accepted: 08/03/2022] [Indexed: 12/10/2022] Open
Abstract
This study aimed to determine how transcutaneous vagus nerve stimulation (tVNS) alters autonomic nervous activity by comparing the effects of different tVNS frequencies and current intensities. We also investigated the sex-dependent autonomic response to tVNS. Thirty-five healthy adult participants were stimulated using a tVNS stimulator at the left cymba conchae while sitting on a reclining chair; tVNS-induced waveform changes were then recorded for different stimulus frequencies (Experiment 1: 3.0 mA at 100 Hz, 25 Hz, 10 Hz, 1 Hz, and 0 Hz (no stimulation)) and current intensities (Experiment 2: 100 Hz at 3.0 mA, 1.0 mA, 0.2 mA (below sensory threshold), and 0 mA (no stimulation)) using an electrocardiogram. Pulse widths were set at 250 µs in both experiment 1 and 2. Changes in heart rate (HR), root-mean-square of the difference between two successive R waves (RMSSD), and the ratio between low-frequency (LF) (0.04–0.15 Hz) and high-frequency (HF) (0.15–0.40 Hz) bands (LF/HF) in spectral analysis, which indicates sympathetic and parasympathetic activity, respectively, in heart rate variability (HRV), were recorded for analysis. Although stimulation at all frequencies significantly reduced HR (p = 0.001), stimulation at 100 Hz had the most pronounced effect (p = 0.001) in Experiment 1 and was revealed to be required to deliver at 3.0 mA in Experiment 2 (p = 0.003). Additionally, participants with higher baseline sympathetic activity experienced higher parasympathetic response during stimulation, and sex differences may exist in the autonomic responses by the application of tVNS. Therefore, our findings suggest that optimal autonomic changes induced by tVNS to the left cymba conchae vary depending on stimulating parameters and sex.
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Affiliation(s)
- Hirotake Yokota
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Correspondence: ; Tel.: +81-25-257-4723
| | - Mutsuaki Edama
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
| | - Ryo Hirabayashi
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
| | - Chie Sekine
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
| | - Naofumi Otsuru
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
| | - Kei Saito
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
| | - Sho Kojima
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
| | - Shota Miyaguchi
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
| | - Hideaki Onishi
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata 950-3198, Japan
- Department of Physical Therapy, Niigata University of Health and Welfare, Niigata 950-3198, Japan
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Ahmed U, Chang YC, Lopez MF, Wong J, Datta-Chaudhuri T, Rieth L, Al-Abed Y, Zanos S. Implant- and anesthesia-related factors affecting cardiopulmonary threshold intensities for vagus nerve stimulation. J Neural Eng 2021; 18. [PMID: 34036940 DOI: 10.1088/1741-2552/ac048a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Accepted: 05/24/2021] [Indexed: 11/11/2022]
Abstract
Objective.Vagus nerve stimulation (VNS) is typically delivered at increasing stimulus intensity until a neurological or physiological response is observed ('threshold') for dose calibration, preclinically and therapeutically. Factors affecting VNS thresholds have not been studied systematically. In a rodent model of VNS we measured neural and physiological responses to increasing VNS intensity, determined neurological and physiological thresholds and examined the effect of implant- and anesthesia-related factors on thresholds.Approach.In acute and chronic vagus implants (45 and 20 rats, respectively) VNS was delivered under isoflurane, ketamine-xylazine, or awake conditions. Evoked compound action potentials (CAPs) were recorded and activation of different fiber types was extracted. Elicited physiological responses were registered, including changes in heart rate (HR), breathing rate (BR), and blood pressure (BP). CAP and physiological thresholds were determined.Main results. The threshold for evoking discernable CAPs (>10µV) (CAP threshold) is significantly lower than what elicits 5%-10% drop in heart rate (heart rate threshold, HRT) (25µA ± 1.8 vs. 80µA ± 5.1, respectively; mean ± SEM). Changes in BP and small changes in BR (bradypnea) occur at lowest intensities (70µA ± 8.3), followed by HR changes (80µA ± 5.1) and finally significant changes in BR (apnea) (310μA ± 32.5). HRT and electrode impedance are correlated in chronic (Pearson correlationr= 0.47;p< 0.001) but not in acute implants (r= -0.34;pNS); HRT and impedance both increase with implant age (r= 0.44;p< 0.001 andr= 0.64;p< 0.001, respectively). HRT is lowest when animals are awake (200µA ± 35.5), followed by ketamine-xylazine (640µA ± 151.5), and isoflurane (1000µA ± 139.5). The sequence of physiological responses with increasing VNS intensity is the same in anesthetized and awake animals. Pulsing frequency affects physiological responses but not CAPs.Significance. Implant age, electrode impedance, and type of anesthesia affect VNS thresholds and should be accounted for when calibrating stimulation dose.
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Affiliation(s)
- Umair Ahmed
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
| | - Yao-Chuan Chang
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
| | - Maria F Lopez
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
| | - Jason Wong
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
| | - Timir Datta-Chaudhuri
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
| | - Loren Rieth
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
| | - Yousef Al-Abed
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
| | - Stavros Zanos
- Institute of Bioelectronic Medicine, Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY 11030, United States of America
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Yaghouby F, Jang K, Hoang U, Asgari S, Vasudevan S. Sex Differences in Vagus Nerve Stimulation Effects on Rat Cardiovascular and Immune Systems. Front Neurosci 2020; 14:560668. [PMID: 33240036 PMCID: PMC7677457 DOI: 10.3389/fnins.2020.560668] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Accepted: 09/22/2020] [Indexed: 01/09/2023] Open
Abstract
Background Investigations into the benefits of vagus nerve stimulation (VNS) through pre-clinical and clinical research have led to promising findings for treating several disorders. Despite proven effectiveness of VNS on conditions such as epilepsy and depression, understanding of off-target effects and contributing factors such as sex differences can be beneficial to optimize therapy design. New Methods In this article, we assessed longitudinal effects of VNS on cardiovascular and immune systems, and studied potential sex differences using a rat model of long-term VNS. Rats were implanted with cuff electrodes around the left cervical vagus nerve for VNS, and wireless physiological monitoring devices for continuous monitoring of cardiovascular system using electrocardiogram (ECG) signals. ECG morphology and heart rate variability (HRV) features were extracted to assess cardiovascular changes resulting from VNS in short-term and long-term timescales. We also assessed VNS effects on expression of inflammatory cytokines in blood during the course of the experiment. Statistical analysis was performed to compare results between Treatment and Sham groups, and between male and female animals from Treatment and Sham groups. Results Considerable differences between male and female rats in cardiovascular effects of VNS were observed in multiple cardiovascular features. However, the effects seemed to be transient with approximately 1-h recovery after VNS. While short-term cardiovascular effects were mainly observed in male rats, females in general showed more significant long-term effects even after VNS stopped. We did not observe notable changes or sex differences in systemic cytokine levels resulting from VNS. Comparison With Existing Methods Compared to existing methods, our study design incorporated wireless physiological monitoring and systemic blood cytokine level analysis, along with long-term VNS experiments in unanesthetized rats to study sex differences. Conclusion The contribution of sex differences for long-term VNS off-target effects on cardiovascular and immune systems was assessed using awake behaving rats. Although VNS did not change the concentration of inflammatory biomarkers in systemic circulation for male and female rats, we observed significant differences in cardiovascular effects of VNS characterized using ECG morphology and HRV analyses.
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Affiliation(s)
- Farid Yaghouby
- U.S. Food and Drug Administration, Center for Devices and Radiological Health (CDRH), Office of Science and Engineering Laboratory (OSEL), Division of Biomedical Physics (DBP), Silver Spring, MD, United States
| | - Kee Jang
- U.S. Food and Drug Administration, Center for Devices and Radiological Health (CDRH), Office of Science and Engineering Laboratory (OSEL), Division of Biomedical Physics (DBP), Silver Spring, MD, United States
| | - Uyen Hoang
- U.S. Food and Drug Administration, Center for Devices and Radiological Health (CDRH), Office of Science and Engineering Laboratory (OSEL), Division of Biomedical Physics (DBP), Silver Spring, MD, United States
| | - Sepideh Asgari
- U.S. Food and Drug Administration, Center for Devices and Radiological Health (CDRH), Office of Science and Engineering Laboratory (OSEL), Division of Biomedical Physics (DBP), Silver Spring, MD, United States
| | - Srikanth Vasudevan
- U.S. Food and Drug Administration, Center for Devices and Radiological Health (CDRH), Office of Science and Engineering Laboratory (OSEL), Division of Biomedical Physics (DBP), Silver Spring, MD, United States
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Pelot NA, Goldhagen GB, Cariello JE, Musselman ED, Clissold KA, Ezzell JA, Grill WM. Quantified Morphology of the Cervical and Subdiaphragmatic Vagus Nerves of Human, Pig, and Rat. Front Neurosci 2020; 14:601479. [PMID: 33250710 PMCID: PMC7672126 DOI: 10.3389/fnins.2020.601479] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 10/13/2020] [Indexed: 12/27/2022] Open
Abstract
It is necessary to understand the morphology of the vagus nerve (VN) to design and deliver effective and selective vagus nerve stimulation (VNS) because nerve morphology influences fiber responses to electrical stimulation. Specifically, nerve diameter (and thus, electrode-fiber distance), fascicle diameter, fascicular organization, and perineurium thickness all significantly affect the responses of nerve fibers to electrical signals delivered through a cuff electrode. We quantified the morphology of cervical and subdiaphragmatic VNs in humans, pigs, and rats: effective nerve diameter, number of fascicles, effective fascicle diameters, proportions of endoneurial, perineurial, and epineurial tissues, and perineurium thickness. The human and pig VNs were comparable sizes (∼2 mm cervically; ∼1.6 mm subdiaphragmatically), while the rat nerves were ten times smaller. The pig nerves had ten times more fascicles-and the fascicles were smaller-than in human nerves (47 vs. 7 fascicles cervically; 38 vs. 5 fascicles subdiaphragmatically). Comparing the cervical to the subdiaphragmatic VNs, the nerves and fascicles were larger at the cervical level for all species and there were more fascicles for pigs. Human morphology generally exhibited greater variability across samples than pigs and rats. A prior study of human somatic nerves indicated that the ratio of perineurium thickness to fascicle diameter was approximately constant across fascicle diameters. However, our data found thicker human and pig VN perineurium than those prior data: the VNs had thicker perineurium for larger fascicles and thicker perineurium normalized by fascicle diameter for smaller fascicles. Understanding these differences in VN morphology between preclinical models and the clinical target, as well as the variability across individuals of a species, is essential for designing suitable cuff electrodes and stimulation parameters and for informing translation of preclinical results to clinical application to advance the therapeutic efficacy of VNS.
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Affiliation(s)
- Nicole A. Pelot
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Gabriel B. Goldhagen
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Jake E. Cariello
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Eric D. Musselman
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Kara A. Clissold
- Histology Research Core, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - J. Ashley Ezzell
- Histology Research Core, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Warren M. Grill
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
- Department of Electrical and Computer Engineering, Duke University, Durham, NC, United States
- Department of Neurobiology, Duke University, Durham, NC, United States
- Department of Neurosurgery, School of Medicine, Duke University, Durham, NC, United States
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10
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Pelot NA, Grill WM. In vivo quantification of excitation and kilohertz frequency block of the rat vagus nerve. J Neural Eng 2020; 17:026005. [PMID: 31945746 DOI: 10.1088/1741-2552/ab6cb6] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE There is growing interest in treating diseases by electrical stimulation and block of peripheral autonomic nerves, but a paucity of studies on the excitation and block of small-diameter autonomic axons. We conducted in vivo quantification of the strength-duration properties, activity-dependent slowing (ADS), and responses to kilohertz frequency (KHF) signals for the rat vagus nerve (VN). APPROACH We conducted acute in vivo experiments in urethane-anaesthetized rats. We placed two cuff electrodes on the left cervical VN and one cuff electrode on the anterior subdiaphragmatic VN. The rostral cervical cuff was used to deliver pulses to quantify recruitment and ADS. The caudal cervical cuff was used to deliver KHF signals. The subdiaphragmatic cuff was used to record compound action potentials (CAPs). MAIN RESULTS We quantified the input-output recruitment and strength-duration curves. Fits to the data using standard strength-duration equations were qualitatively similar, but the resulting chronaxie and rheobase estimates varied substantially. We measured larger thresholds for the slowest fibres (0.5-1 m s-1), especially at shorter pulse widths. Using a novel cross-correlation CAP-based analysis, we measured ADS of ~2.3% after 3 min of 2 Hz stimulation, which is comparable to the ADS reported for sympathetic efferents in somatic nerves, but much smaller than the ADS in cutaneous nociceptors. We found greater ADS with higher stimulation frequency and non-monotonic changes in CV in select cases. We found monotonically increasing block thresholds across frequencies from 10 to 80 kHz for both fast and slow fibres. Further, following 25 s of KHF signal, neural conduction could require tens of seconds to recover. SIGNIFICANCE The quantification of mammalian autonomic nerve responses to conventional and KHF signals provides essential information for the development of peripheral nerve stimulation therapies and for understanding their mechanisms of action.
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Affiliation(s)
- N A Pelot
- Department of Biomedical Engineering, Duke University, Room 1427, Fitzpatrick CIEMAS, 101 Science Drive, Campus Box 90281, Durham, NC 27708, United States of America
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Rodrigues F, Ribeiro JF, Anacleto PA, Fouchard A, David O, Sarro PM, Mendes PM. Fabrication and characterization of polyimide-based 'smooth' titanium nitride microelectrode arrays for neural stimulation and recording. J Neural Eng 2019; 17:016010. [PMID: 31614339 DOI: 10.1088/1741-2552/ab4dbb] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
OBJECTIVE As electrodes are required to interact with sub-millimeter neural structures, innovative microfabrication processes are required to enable fabrication of microdevices involved in such stimulation and/or recording. This requires the development of highly integrated and miniaturized systems, comprising die-integration-compatible technology and flexible microelectrodes. To elicit selective stimulation and recordings of sub-neural structures, such microfabrication process flow can beneficiate from the integration of titanium nitride (TiN) microelectrodes onto a polyimide substrate. Finally, assembling onto cuffs is required, as well as electrode characterization. APPROACH Flexible TiN microelectrode array integration and miniaturization was achieved through microfabrication technology based on microelectromechanical systems (MEMS) and complementary metal-oxide semiconductor processing techniques and materials. They are highly reproducible processes, granting extreme control over the feature size and shape, as well as enabling the integration of on-chip electronics. This design is intended to enhance the integration of future electronic modules, with high gains on device miniaturization. MAIN RESULTS (a) Fabrication of two electrode designs, (1) 2 mm long array with 14 TiN square-shaped microelectrodes (80 × 80 µm2), and (2) an electrode array with 2 mm × 80 µm contacts. The average impedances at 1 kHz were 59 and 5.5 kΩ, respectively, for the smaller and larger contacts. Both designs were patterned on a flexible substrate and directly interconnected with a silicon chip. (b) Integration of flexible microelectrode array onto a cuff electrode designed for acute stimulation of the sub-millimeter nerves. (c) The TiN electrodes exhibited capacitive charge transfer, a water window of -0.6 V to 0.8 V, and a maximum charge injection capacity of 154 ± 16 µC cm-2. SIGNIFICANCE We present the concept, fabrication and characterization of composite and flexible cuff electrodes, compatible with post-processing and MEMS packaging technologies, which allow for compact integration with control, readout and RF electronics. The fabricated TiN microelectrodes were electrochemically characterized and exhibited a comparable performance to other state-of-the-art electrodes for neural stimulation and recording. Therefore, the presented TiN-on-polyimide microelectrodes, released from silicon wafers, are a promising solution for neural interfaces targeted at sub-millimeter nerves, which may benefit from future upgrades with die-electronic modules.
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Affiliation(s)
- F Rodrigues
- CMEMS-UMinho, University of Minho, Braga, Portugal. Electronics Components, Technology, and Materials Lab, Else Kooi Laboratory, Delft University of Technology, Delft, The Netherlands. Author to whom any correspondence should be addressed
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12
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Ravagli E, Mastitskaya S, Thompson N, Aristovich K, Holder D. Optimization of the electrode drive pattern for imaging fascicular compound action potentials in peripheral nerve with fast neural electrical impedance tomography. Physiol Meas 2019; 40:115007. [PMID: 31694004 PMCID: PMC7214787 DOI: 10.1088/1361-6579/ab54eb] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE The main objective of this study was to investigate which injection pattern led to the best imaging of fascicular compound activity in fast neural EIT of peripheral nerve using an external cylindrical 2 × 14-electrodes cuff. Specifically, the study addressed the identification of the optimal injection pattern and of the optimal region of the reconstructed volume to image fascicles. APPROACH The effect of three different measurement protocol features (transversal/longitudinal injection, drive electrode spacing, referencing configuration) over imaging was investigated in simulation with the use of realistic impedance changes and noise levels. Image-based metrics were employed to evaluate the quality of the reconstructions over the reconstruction domain. The optimal electrode addressing protocol suggested by the simulations was validated in vivo on the tibial and peroneal fascicles of rat sciatic peripheral nerves (N = 3) against MicroCT reference images. MAIN RESULTS Injecting current transversally, with spacing of ⩾4 electrodes apart (⩾100°) and single-ring referencing of measurements, led to the best overall localization when reconstructing on the edge of the electrode array closest to the reference. Longitudinal injection protocols led to a higher SNR of the reconstructed image but poorer localization. All in vivo EIT recordings had statistically significant impedance variations (p < 0.05). Overall, fascicle center-of-mass (CoM) localization error was estimated at 141 ± 56 µm (-26 ± 94 µm and 5 ± 29° in radial coordinates). Significant difference was found (p < 0.05) between mean angular location of the tibial and peroneal CoMs. SIGNIFICANCE This study gives the reader recommendations for performing fast neural EIT of fascicular compound activity using the most effective protocol features.
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Affiliation(s)
- Enrico Ravagli
- Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
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Fontanesi LB, Fazan FS, Dias FJ, Schiavoni MCL, Marques Jr. W, Fazan VPS. Sensory and Motor Conduction Velocity in Spontaneously Hypertensive Rats: Sex and Aging Investigation. Front Syst Neurosci 2019; 13:62. [PMID: 31736720 PMCID: PMC6838635 DOI: 10.3389/fnsys.2019.00062] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 10/10/2019] [Indexed: 11/29/2022] Open
Abstract
The literature is extensive on how hypertension affects the morphology and function of the central nervous system (CNS) and is being focused on multiple organ damage involving the kidneys, heart, endothelium and retina. Hypertension damage to the peripheral nervous system is less explored in the literature. We have previously shown morphometric alterations in large and small caliber myelinated fibers of nerves in the adult spontaneously hypertensive rat (SHR). However, the functional correlation of these findings has not been explored. We performed an electrophysiological investigation of hind limb nerves in SHR of both genders in different ages. Normotensive Wistar-Kyoto (WKY) rats were used as controls. Electrophysiological recordings and determination of motor (MCV) and sensory (SCV) nerve conduction velocity were performed in the same animals at four different ages: 5, 8, 20 and 40 weeks after birth. Comparisons were made between ages, genders and animal strain. We showed a continuous body weight increase in adult life in all animals studied. MCV got stable at 20-week old hypertensive animals and continued to increase in normotensive ones. The SCV was constant between the ages of 20 and 40 weeks old in female SHR and decreased in male SHR while it continued to increase in WKY animals. The electrophysiological investigation of the nerves in WKY and SHR from both genders and different ages, associated with morphological and morphometric data from the literature suggest that hypertension affects the nerve function and might corroborate the development of a peripheral neuropathy.
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Affiliation(s)
- Lucas B. Fontanesi
- Department of Neuroscience and Behavioral Science, School of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, Brazil
| | - Frederico S. Fazan
- Department of Physiology, Paulista School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Fernando J. Dias
- Department of Integral Dentistry, CICO—Research Center in Dental Sciences, Dental School, Universidad de La Frontera (UFRo), Temuco, Chile
| | - Maria Cristina L. Schiavoni
- Department of Neuroscience and Behavioral Science, School of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, Brazil
| | - Wilson Marques Jr.
- Department of Neuroscience and Behavioral Science, School of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, Brazil
| | - Valéria Paula Sassoli Fazan
- Department of Neuroscience and Behavioral Science, School of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, Brazil
- Department of Surgery and Anatomy, School of Medicine of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, Brazil
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Joseph B, Shimojo G, Li Z, Thompson-Bonilla MDR, Shah R, Kanashiro A, Salgado HC, Ulloa L. Glucose Activates Vagal Control of Hyperglycemia and Inflammation in Fasted Mice. Sci Rep 2019; 9:1012. [PMID: 30700738 PMCID: PMC6354016 DOI: 10.1038/s41598-018-36298-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 11/14/2018] [Indexed: 11/18/2022] Open
Abstract
Sepsis is a leading cause of death in hospitalized patients. Many experimental treatments may have failed in clinical trials for sepsis, in part, because they focused on immune responses of healthy animals that did not mimic the metabolic settings of septic patients. Epidemiological studies show an association between metabolic and immune alterations and over 1/3 of septic patients are diabetic, but the mechanism linking these systems is unknown. Here, we report that metabolic fasting increased systemic inflammation and worsened survival in experimental sepsis. Feeding and administration of glucose in fasted mice activated the vagal tone without affecting blood pressure. Vagal stimulation attenuated hyperglycemia and serum TNF levels in sham but only hyperglycemia in splenectomized mice. Vagal stimulation induced the production of dopamine from the adrenal glands. Experimental diabetes increased hyperglycemia and systemic inflammation in experimental sepsis. Fenoldopam, a specific dopaminergic type-1 agonist, attenuated hyperglycemia and systemic inflammation in diabetic endotoxemic mice. These results indicate that glucose activates vagal control of hyperglycemia and inflammation in fasted septic mice via dopamine.
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Affiliation(s)
- Biju Joseph
- Department of Surgery, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA
| | - Guilherme Shimojo
- Department of Surgery, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA
| | - Zhifeng Li
- Department of Surgery, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA
| | - Maria Del Rocio Thompson-Bonilla
- Department of Surgery, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA
- Hospital "October 1st", ISSSTE", 1669 National Polytechnic Institute Ave, Mexico City, Mexico
| | - Roshan Shah
- Department of Surgery, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA
| | - Alexandre Kanashiro
- Department of Surgery, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA
- Department of Physiology, Medical School - University of São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
| | - Helio C Salgado
- Department of Physiology, Medical School - University of São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
| | - Luis Ulloa
- Department of Surgery, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA.
- Center for Immunity and Inflammation, Rutgers-New Jersey Medical School, Newark, NJ, 07103, USA.
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Burger AM, Van Diest I, van der Does W, Hysaj M, Thayer JF, Brosschot JF, Verkuil B. Transcutaneous vagus nerve stimulation and extinction of prepared fear: A conceptual non-replication. Sci Rep 2018; 8:11471. [PMID: 30065275 PMCID: PMC6068181 DOI: 10.1038/s41598-018-29561-w] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 07/10/2018] [Indexed: 12/17/2022] Open
Abstract
Transcutaneous stimulation of the auricular branch of the vagus nerve (tVNS) may accelerate fear extinction in healthy humans. Here, we aimed to investigate this hypothesis in healthy young participants in a prepared learning paradigm, using spider pictures as conditioned stimuli. After a fear conditioning phase, participants were randomly allocated to receive tVNS (final N = 42) or sham stimulation (final N = 43) during an extinction phase. Conditioned fear was assessed using US expectancy ratings, skin conductance and fear potentiated startle responses. After successful fear acquisition, participants in both groups showed a reduction of fear over the course of the extinction phase. There were no between-group differences in extinction rates for physiological indices of fear. Contrary to previous findings, participants in the tVNS condition also did not show accelerated declarative extinction learning. Participants in the tVNS condition did have lower initial US expectancy ratings for the CS− trials than those who received sham stimulation, which may indicate an enhanced processing of safety cues due to tVNS. In conclusion, the expected accelerated extinction due to tVNS was not observed. The results from this study call for more research on the optimal tVNS stimulation intensity settings.
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Affiliation(s)
- Andreas M Burger
- Institute of Psychology, Leiden University, Wassenaarseweg 52, 2333, AK, Leiden, The Netherlands. .,Faculty of Psychology, Katholieke Universiteit Leuven, Tiensestraat 102, 3000, Leuven, Belgium.
| | - Ilse Van Diest
- Faculty of Psychology, Katholieke Universiteit Leuven, Tiensestraat 102, 3000, Leuven, Belgium
| | - Willem van der Does
- Institute of Psychology, Leiden University, Wassenaarseweg 52, 2333, AK, Leiden, The Netherlands
| | - Marsida Hysaj
- Institute of Psychology, Leiden University, Wassenaarseweg 52, 2333, AK, Leiden, The Netherlands
| | - Julian F Thayer
- Department of Psychology, The Ohio State University, 1835 Neil Avenue Mall, Columbus, OH, 43210, United States
| | - Jos F Brosschot
- Institute of Psychology, Leiden University, Wassenaarseweg 52, 2333, AK, Leiden, The Netherlands
| | - Bart Verkuil
- Institute of Psychology, Leiden University, Wassenaarseweg 52, 2333, AK, Leiden, The Netherlands
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Pelot NA, Thio BJ, Grill WM. Modeling Current Sources for Neural Stimulation in COMSOL. Front Comput Neurosci 2018; 12:40. [PMID: 29937722 PMCID: PMC6002501 DOI: 10.3389/fncom.2018.00040] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 05/17/2018] [Indexed: 11/13/2022] Open
Abstract
Background: Computational modeling provides an important toolset for designing and analyzing neural stimulation devices to treat neurological disorders and diseases. Modeling enables efficient exploration of large parameter spaces, where preclinical and clinical studies would be infeasible. Current commercial finite element method software packages enable straightforward calculation of the potential distributions, but it is not always clear how to implement boundary conditions to appropriately represent metal stimulating electrodes. By quantifying the effects of different electrode representations on activation thresholds for model axons, we provide recommendations for accurate and efficient modeling of neural stimulating electrodes. Methods: We quantified the effects of different representations of current sources for neural stimulation in COMSOL Multiphysics for monopolar, bipolar, and multipolar electrode designs. Results: We recommend modeling each electrode contact as a thin platinum domain, modeling the electrode substrate with the conductivity of silicone, and either using a point current source in the center of each electrode contact or using a boundary current source. Alternatively, to avoid possible numerical instabilities associated with a large range of conductivity values (i.e., platinum and silicone) and to eliminate the small mesh elements required for thin electrode contacts, the electrode substrate can be assigned the conductivity of platinum by using insulating boundaries between the substrate and surrounding medium, and within the substrate to isolate the contacts from each other. When modeling more than one contact, we recommend using superposition by solving the model once for each contact, leaving inactive contacts floating, and superposing the resulting potentials. We computed comparable errors in activation thresholds across the different implementations in a simplified model (electrode in a homogeneous, isotropic medium), and in realistic models of rat spinal cord stimulation (SCS) and human deep brain stimulation, indicating that the recommended approaches are applicable to different stimulation targets.
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Affiliation(s)
- Nicole A Pelot
- Department of Biomedical Engineering, Duke University Durham, NC, United States
| | - Brandon J Thio
- Department of Biomedical Engineering, Duke University Durham, NC, United States
| | - Warren M Grill
- Department of Biomedical Engineering, Duke University Durham, NC, United States.,Department of Electrical and Computer Engineering, Duke University Durham, NC, United States.,Department of Neurobiology, Duke University Durham, NC, United States.,Department of Neurosurgery, Duke University School of Medicine Durham, NC, United States
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Effects of short and prolonged transcutaneous vagus nerve stimulation on heart rate variability in healthy subjects. Auton Neurosci 2017; 203:88-96. [DOI: 10.1016/j.autneu.2016.11.003] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 10/19/2016] [Accepted: 11/25/2016] [Indexed: 01/14/2023]
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A New Method for Automated Identification and Morphometry of Myelinated Fibers Through Light Microscopy Image Analysis. J Digit Imaging 2017; 29:63-72. [PMID: 25986589 DOI: 10.1007/s10278-015-9804-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Nerve morphometry is known to produce relevant information for the evaluation of several phenomena, such as nerve repair, regeneration, implant, transplant, aging, and different human neuropathies. Manual morphometry is laborious, tedious, time consuming, and subject to many sources of error. Therefore, in this paper, we propose a new method for the automated morphometry of myelinated fibers in cross-section light microscopy images. Images from the recurrent laryngeal nerve of adult rats and the vestibulocochlear nerve of adult guinea pigs were used herein. The proposed pipeline for fiber segmentation is based on the techniques of competitive clustering and concavity analysis. The evaluation of the proposed method for segmentation of images was done by comparing the automatic segmentation with the manual segmentation. To further evaluate the proposed method considering morphometric features extracted from the segmented images, the distributions of these features were tested for statistical significant difference. The method achieved a high overall sensitivity and very low false-positive rates per image. We detect no statistical difference between the distribution of the features extracted from the manual and the pipeline segmentations. The method presented a good overall performance, showing widespread potential in experimental and clinical settings allowing large-scale image analysis and, thus, leading to more reliable results.
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Rational Roots of Sympathetic Overactivity by Neurogenic Pulmonary Edema Modeling Arising from Sympathyco-Vagal Imbalance in Subarachnoid Hemorrhage: An Experimental Study. World Neurosurg 2016; 92:463-470. [DOI: 10.1016/j.wneu.2016.04.067] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 04/17/2016] [Accepted: 04/20/2016] [Indexed: 12/21/2022]
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Nukada H, Baba M, Ogasawara S, McMorran D, Yagihashi S. Neuropathy in the spontaneously hypertensive rat: An electrophysiological and histological study. Muscle Nerve 2016; 54:756-62. [PMID: 26970072 DOI: 10.1002/mus.25098] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 02/24/2016] [Accepted: 03/03/2016] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Hypertension is identified as a risk factor for development of polyneuropathy. In this study we examined nerve conduction and morphological alteration of peripheral nerves in spontaneously hypertensive rats (SHR). METHODS Motor nerve conduction velocity (MNCV) in the sciatic-tibial nerve and sensory nerve conduction velocity (SNCV) in the sural nerve were measured. Pathological investigations included spinal cord, dorsal root ganglion, and hindlimb nerves in SHR and Wistar-Kyoto rats (WKY) aged 4-64 weeks. RESULTS Blood pressure was significantly higher in SHR than WKY animals at 4 weeks and elevated further with aging. MNCV and SNCV were significantly slower in SHR compared with WKY after age 24 weeks. Prominent morphological changes in SHR nerves included axonal atrophy and myelin splitting. SHR also had endoneurial microangiopathy with reduplication of basement membrane. CONCLUSIONS SHR showed slowed nerve conduction velocity and pathological abnormalities of hindlimb nerves. Sustained severe hypertension may cause axonal atrophy and endoneurial microangiopathy. Muscle Nerve 54: 756-762, 2016.
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Affiliation(s)
- Hitoshi Nukada
- The Nukada Institute for Medical & Biological Research, 5-18 Inage-machi, Inage-ku, Chiba, 263-0035, Japan. .,Department of Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
| | - Masayuki Baba
- Department of Neurology, Aomori Prefectural Central Hospital, Aomori, Japan
| | - Saori Ogasawara
- Department of Pathology and Molecular Medicine, Hirosaki University, Hirosaki, Japan
| | - Denise McMorran
- Department of Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Soroku Yagihashi
- Department of Pathology and Molecular Medicine, Hirosaki University, Hirosaki, Japan
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Koresh O, Kaplan Z, Zohar J, Matar MA, Geva AB, Cohen H. Distinctive cardiac autonomic dysfunction following stress exposure in both sexes in an animal model of PTSD. Behav Brain Res 2016; 308:128-42. [PMID: 27105958 DOI: 10.1016/j.bbr.2016.04.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 04/12/2016] [Accepted: 04/14/2016] [Indexed: 11/16/2022]
Abstract
It is unclear whether the poor autonomic flexibility or dysregulation observed in patients with posttraumatic stress disorder (PTSD) represents a pre-trauma vulnerability factor or results from exposure to trauma. We used an animal model of PTSD to assess the association between the behavioral response to predator scent stress (PSS) and the cardiac autonomic modulation in male and female rats. The rats were surgically implanted with radiotelemetry devices to measure their electrocardiograms and locomotor activity (LMA). Following baseline telemetric monitoring, the animals were exposed to PSS or sham-PSS. Continuous telemetric monitoring (24h/day sampling) was performed over the course of 7days. The electrocardiographic recordings were analyzed using the time- and frequency-domain indexes of heart rate variability (HRV). The behavioral response patterns were assessed using the elevated plus maze and acoustic startle response paradigms for the retrospective classification of individuals according to the PTSD-related cut-off behavioral criteria. During resting conditions, the male rats had significantly higher heart rates (HR) and lower HRV parameters than the female rats during both the active and inactive phases of the daily cycle. Immediately after PSS exposure, both the female and male rats demonstrated a robust increase in HR and a marked drop in HRV parameters, with a shift of sympathovagal balance towards sympathetic predominance. In both sexes, autonomic system habituation and recovery were selectively inhibited in the rats whose behavior was extremely disrupted after exposure to PSS. However, in the female rats, exposure to the PSS produced fewer EBR rats, with a more rapid recovery curve than that of the male rats. PSS did not induce changes to the circadian rhythm of the LMA. According to our results, PTSD can be conceptualized as a disorder that is related to failure-of-recovery mechanisms that impede the restitution of physiological homeostasis.
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Affiliation(s)
- Ori Koresh
- Beer-Sheva Mental Health Center, The State of Israel Ministry of Health, Anxiety and Stress Research Unit, Faculty of Health Sciences, Ben-Gurion University of the Negev, Israel
| | - Zeev Kaplan
- Beer-Sheva Mental Health Center, The State of Israel Ministry of Health, Anxiety and Stress Research Unit, Faculty of Health Sciences, Ben-Gurion University of the Negev, Israel
| | - Joseph Zohar
- Division of Psychiatry, The State of Israel Ministry of Health, The Chaim Sheba Medical Center, Ramat-Gan, Israel, Sackler Medical School, Tel-Aviv University, Israel
| | - Michael A Matar
- Beer-Sheva Mental Health Center, The State of Israel Ministry of Health, Anxiety and Stress Research Unit, Faculty of Health Sciences, Ben-Gurion University of the Negev, Israel
| | - Amir B Geva
- Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Hagit Cohen
- Beer-Sheva Mental Health Center, The State of Israel Ministry of Health, Anxiety and Stress Research Unit, Faculty of Health Sciences, Ben-Gurion University of the Negev, Israel.
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Pianca E, Krause Neto W, Pithon-Curi TC, Gama EF, Sabbag A, Souza RRD. Endurance training induces structural and morphoquantitative changes in rat vagus nerve. REV BRAS MED ESPORTE 2015. [DOI: 10.1590/1517-869220152105143990] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
ABSTRACT Introduction: Many nervous system tissues and cells suffers positive changes when faced to exercise training. However, data on vagus nerve adaptation from exercise-induced study is absent. Objective: To analyze the effect of an endurance training on the vagus nerve morphology of rats. Methods: Wistar rats (6 months of age) were divided into two groups: control group (CG, n=8), and aerobic trained group (AT, n=8). AT was submitted to a treadmill training program of five times per week during 12 weeks. The maximum speed stipulated in the training protocol corresponded to 60% of the mean maximum intensity achieved by the group in the test of maximum effort. Results: Twelve weeks of treadmill training resulted in left ventricular hypertrophy in the AT group com-pared to CG. There was a significant increase in the area of both the myelinated and unmyelinated axons, and in the area of myelin sheath with training. The number of neurotubules and neurofilaments in myelinated fibers of aerobic trained group was significantly greater than CG (p≤0.05). Conclusion: Endurance training promoted significant increase in morphometric parameters of the vagus nerve in the same way it affect somatic nerves.
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Affiliation(s)
- Eduardo Pianca
- Universidade São Judas Tadeu, Brazil; Universidade de Guarulhos, Brazil
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da Silva GAR, de Aguiar Mendes VA, Genari AB, Castania JA, Salgado HC, Fazan VPS. Recurrent laryngeal nerve alterations in developing spontaneously hypertensive rats. Laryngoscope 2015; 126:E40-7. [DOI: 10.1002/lary.25426] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 03/16/2015] [Accepted: 05/18/2015] [Indexed: 11/05/2022]
Affiliation(s)
- Greice Anne Rodrigues da Silva
- Department of Neuroscience and Behavioral Sciences; School of Medicine of Ribeirão Preto, University of São Paulo; Ribeirão Preto São Paulo Brazil
| | - Vania Alice de Aguiar Mendes
- Department of Neuroscience and Behavioral Sciences; School of Medicine of Ribeirão Preto, University of São Paulo; Ribeirão Preto São Paulo Brazil
| | - Adriana Borges Genari
- Department of Neuroscience and Behavioral Sciences; School of Medicine of Ribeirão Preto, University of São Paulo; Ribeirão Preto São Paulo Brazil
| | - Jaci Ayrton Castania
- Department of Physiology; School of Medicine of Ribeirão Preto, University of São Paulo; Ribeirão Preto São Paulo Brazil
| | - Hélio Cesar Salgado
- Department of Physiology; School of Medicine of Ribeirão Preto, University of São Paulo; Ribeirão Preto São Paulo Brazil
| | - Valéria Paula Sassoli Fazan
- Department of Neuroscience and Behavioral Sciences; School of Medicine of Ribeirão Preto, University of São Paulo; Ribeirão Preto São Paulo Brazil
- Department of Surgery and Anatomy; School of Medicine of Ribeirão Preto, University of São Paulo; Ribeirão Preto São Paulo Brazil
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Sanada LS, Tavares MR, Sato KL, Ferreira RDS, Neubern MCM, Castania JA, Salgado HC, Fazan VPS. Association of chronic diabetes and hypertension in sural nerve morphometry: an experimental study. Diabetol Metab Syndr 2015; 7:9. [PMID: 25717348 PMCID: PMC4339238 DOI: 10.1186/s13098-015-0005-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 02/02/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Prospective studies have shown incidence rates of hypertension in diabetes mellitus to be three times that of subjects without diabetes mellitus. The reverse also applies, with the incidence of diabetes two to three times higher in patients with hypertension. Despite this common clinical association, the contribution of each isolated entity in the development of a neuropathy is still not well understood. The aims of the present study were to investigate the presence of peripheral neuropathy in spontaneously hypertensive rats (SHR) and SHR with chronically induced diabetes, using a morphological and morphometric study of the sural nerves. METHODS Female SHR and normotensive Wistar rats (WR), 8 weeks old, received a single intravenous injection of streptozotocin (STZ) through the tail vein. Controls from both strains received vehicle. Twelve weeks after the injection, sural nerves were dissected and prepared for light microscopy. Morphometry of sural nerve fascicles and myelinated fibers was performed with the aid of computer software. RESULTS The sural nerve myelinated fibers were highly affected by experimental diabetes in normotensive rats, causing mainly the reduction of the fiber size. Hypertensive rats showed characteristics of small fiber neuropathy and a severe reduction of the number and density or Schwann cells. The association between diabetes and hypertension caused an increase on the average size of the myelinated fibers, pointing to a small fiber loss, associated to axonal atrophy. CONCLUSIONS Our study gives morphological support to the existence of a neuropathy due to hypertension, which is among one of the most common risk factors for diabetic neuropathy. The association between the two neuropathies showed to be a complex alteration, involving and including both, large and small fibers neuropathy. Hypertension caused, indeed, an exacerbation of the alterations already observed in experimental models of diabetic neuropathy.
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Affiliation(s)
- Luciana Sayuri Sanada
- />Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil
| | | | - Karina Laurenti Sato
- />Departament of Physical Therapy, Federal University of Sergipe, Aracaju, SE Brazil
| | - Renata da Silva Ferreira
- />Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil
| | - Milena Cardoso Maia Neubern
- />Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil
| | - Jaci Ayrton Castania
- />Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil
| | - Helio Cesar Salgado
- />Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil
| | - Valéria Paula Sassoli Fazan
- />Department of Neuroscience and Behavioral Neurosciences, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP Brazil
- />Department of Surgery and Anatomy, School of Medicine of Ribeirão Preto, USP, Av. Bandeirantes 3900, Ribeirão Preto, SP Brazil
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Reproducibility in nerve morphometry: comparison between methods and among observers. BIOMED RESEARCH INTERNATIONAL 2013; 2013:682849. [PMID: 23841086 PMCID: PMC3697141 DOI: 10.1155/2013/682849] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Revised: 05/23/2013] [Accepted: 05/24/2013] [Indexed: 11/23/2022]
Abstract
We investigated the reproducibility of a semiautomated method (computerized with manual intervention) for nerve morphometry (counting and measuring myelinated fibers) between three observers with different levels of expertise and experience with the method. Comparisons between automatic (fully computerized) and semiautomated morphometric methods performed by the same computer software using the same nerve images were also performed. Sural nerves of normal adult rats were used. Automatic and semiautomated morphometry of the myelinated fibers were made through the computer software KS-400. Semiautomated morphometry was conducted by three independent observers on the same images, using the semiautomated method. Automatic morphometry overestimated the myelin sheath area, thus overestimating the myelinated fiber size and underestimating the axon size. Fiber distributions overestimation was of 0.5 μm. For the semiautomated morphometry, no differences were found between observers for myelinated fiber and axon size distributions. Overestimation of the myelin sheath size of normal fibers by the fully automatic method might have an impact when morphometry is used for diagnostic purposes. We suggest that not only semiautomated morphometry results can be compared between different centers in clinical trials but it can also be performed by more than one investigator in one single experiment, being a reliable and reproducible method.
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Sanada LS, Tavares MR, Neubern MCM, Salgado HC, Fazan VPS. Can Wistar rats be used as the normotensive controls for nerve morphometry investigations in spontaneously hypertensive rats (SHR)? Acta Cir Bras 2012; 26:514-20. [PMID: 22042117 DOI: 10.1590/s0102-86502011000600018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 08/11/2011] [Indexed: 11/21/2022] Open
Abstract
PURPOSE We compared the sural nerve morphology among Wistar (WR), Wistar-Kyoto (WKY) and Spontaneously hypertensive (SHR) rats, including the nerve fascicles and myelinated fibers morphometry. METHODS Age matched (20 weeks) female WR (N=6), WKY (N=6) and SHR (N=7) had their right and left sural nerves removed, embedded in epoxy resin, and observed by light microscopy. Morphometric analysis was performed with the aid of computer software. RESULTS Despite presenting the same age, WR were heavier than WKY and SHR, as were SHR compared to WKY. Systolic arterial pressure was higher in SHR compared to WR, but no differences between SHR and WKY or WR and WKY were observed. The sural nerves were morphometrically symmetric between proximal and distal segments on the same side and between sides in all strains with no differences in the myelinated fiber number. Schwann cell number and density were smaller in SHR and G ratio was larger in SHR, indicating that SHR have thinner myelinated fibers. CONCLUSION Sural nerve morphology is similar between WKY and WR, allowing the use of WR as the SHR controls in morphological investigations involving peripheral neuropathies.
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Affiliation(s)
- Luciana Sayuri Sanada
- Department of Neuroscience and Behavioral Neurosciences, FMRP, USP, Ribeirao Preto, SP, Brazil
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Fontanesi LB, Schiavoni MCL, Salgado HC, Fazan VPS. Longitudinal morphometric study of the cervical vagus nerve in young Wistar‐Kyoto rats. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.725.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Lucas Baptista Fontanesi
- Neurosciences and Behavioral NeurosciencesSchool of Medicine of Ribeirão PretoRibeirão PretoBrazil
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Sanada LS, da Rocha Kalil AL, Tavares MR, Neubern MCM, Salgado HC, Fazan VPS. Sural nerve involvement in experimental hypertension: morphology and morphometry in male and female normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). BMC Neurosci 2012; 13:24. [PMID: 22380617 PMCID: PMC3350456 DOI: 10.1186/1471-2202-13-24] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2011] [Accepted: 03/02/2012] [Indexed: 01/20/2023] Open
Abstract
Background The sural nerve has been widely investigated in experimental models of neuropathies but information about its involvement in hypertension was not yet explored. The aim of the present study was to compare the morphological and morphometric aspects of different segments of the sural nerve in male and female spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. Rats aged 20 weeks (N = 6 in each group) were investigated. After arterial pressure and heart rate recordings in anesthetized animals, right and left sural nerves were removed and prepared for epoxy resin embedding and light microscopy. Morphometric analysis was performed with the aid of computer software, and took into consideration the fascicle area and diameter, as well as myelinated fiber number, density, area and diameter. Results Significant differences were observed for the myelinated fiber number and density, comparing different genders of WKY and SHR. Also, significant differences for the morphological (thickening of the endoneural blood vessel walls and lumen reduction) and morphometric (myelinated fibers diameter and G ratio) parameters of myelinated fibers were identified. Morphological exam of the myelinated fibers suggested the presence of a neuropathy due to hypertension in both SHR genders. Conclusions These results indicate that hypertension altered important morphometric parameters related to nerve conduction of sural nerve in hypertensive animals. Moreover the comparison between males and females of WKY and SHR allows the conclusion that the morphological and morphometric parameters of sural nerve are not gender related. The morphometric approach confirmed the presence of neuropathy, mainly associated to the small myelinated fibers. In conclusion, the present study collected evidences that the high blood pressure in SHR is affecting the sural nerve myelinated fibers.
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Affiliation(s)
- Luciana Sayuri Sanada
- Department of Neuroscience and Behavioral Neurosciences, University of São Paulo, Monte Alegre, Ribeirão Preto, Brazil
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Oliveira ALCRD, Fazan VPS, Marques W, Barreira AA. Dorsal cutaneous branch of the ulnar nerve: a light and electron microscopy histometric study. J Peripher Nerv Syst 2011; 16:98-101. [DOI: 10.1111/j.1529-8027.2011.00326.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Rodrigues A, Ferreira R, Salgado H, Fazan V. Morphometric analysis of the phrenic nerve in male and female Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Braz J Med Biol Res 2011; 44:583-91. [DOI: 10.1590/s0100-879x2011007500053] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 04/15/2011] [Indexed: 11/22/2022] Open
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Holmes TJ, Pellegrini M, Miller C, Epplin-Zapf T, Larkin S, Luccarelli S, Staurenghi G. Automated software analysis of corneal micrographs for peripheral neuropathy. Invest Ophthalmol Vis Sci 2010; 51:4480-91. [PMID: 20805570 DOI: 10.1167/iovs.09-4108] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE A relationship has been reported between the presence of peripheral neuropathy and the density and shape of corneal nerve fibers. Peripheral neuropathy is a debilitating condition that arises from many common health problems, and its presence is often confirmed with an invasive clinical test called intramuscular electromyography (EMG). In this study, the possibility of developing an alternative or adjunct test to EMG based on the appearance of nerve fibers in corneal micrographs was explored. Since corneal imaging is virtually noninvasive compared with EMG, such a test may be administered more liberally and frequently, before neuropathy symptoms occur. METHODS A software program that automatically traces nerve fibers in corneal micrographs and generates measures based on these traces was implemented. This software was applied to a database of images collected by confocal laser scanning corneal microscopy from diabetic subjects whose levels of neuropathy were measured with EMG and from healthy subjects. RESULTS Trends in the nerve fiber density and various measures of shape were calculated and observed, to explore the possibility of using these measures as a clinical tool for corroborating symptoms, confirming an evaluation, or evaluating risk factors for developing neuropathy. CONCLUSIONS Preliminary statistical trends show a potential for measuring and observing neuropathy severity or for providing an objective risk measure for a patient's ensuing condition. More work is needed in the development of the measures and in their testing to prove that the measures can be made repeatable in a clinical environment.
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Fazan VPS, Rodrigues Filho OA, Jordão CER, Moore KC. Phrenic nerve diabetic neuropathy in rats: unmyelinated fibers morphometry. J Peripher Nerv Syst 2009; 14:137-45. [PMID: 19691536 DOI: 10.1111/j.1529-8027.2009.00223.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have demonstrated that phrenic nerves' large myelinated fibers in streptozotocin (STZ)-induced diabetic rats show axonal atrophy, which is reversed by insulin treatment. However, studies on structural abnormalities of the small myelinated and the unmyelinated fibers in the STZ-model of neuropathy are limited. Also, structural changes in the endoneural vasculature are not clearly described in this model and require detailed study. We have undertaken morphometric studies of the phrenic nerve in insulin-treated and untreated STZ-diabetic rats and non-diabetic control animals over a 12-week period. The presence of neuropathy was assessed by means of transmission electron microscopy, and morphometry of the unmyelinated fibers was performed. The most striking finding was the morphological evidence of small myelinated fiber neuropathy due to the STZ injection, which was not protected or reversed by conventional insulin treatment. This neuropathy was clearly associated with severe damage of the endoneural vessels present on both STZ groups, besides the insulin treatment. The STZ-diabetes model is widely used to investigate experimental diabetic neuropathies, but few studies have performed a detailed assessment of either unmyelinated fibers or capillary morphology in this animal model. The present study adds useful information for further investigations on the ultrastructural basis of nerve function in diabetes.
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Affiliation(s)
- Valéria Paula S Fazan
- Department of Surgery and Anatomy, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
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Fazan VPS, Rodrigues Filho OA, Jordão CER, Moore KC. Ultrastructural Morphology and Morphometry of Phrenic Nerve in Rats. Anat Rec (Hoboken) 2009; 292:513-7. [DOI: 10.1002/ar.20843] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Almeida MR, Lima EDO, da Silva VJD, Campos MG, Antunes LM, Salman AKD, Dias FL. Genotoxic studies in hypertensive and normotensive rats treated with amiodarone. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2008; 657:155-9. [DOI: 10.1016/j.mrgentox.2008.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2008] [Revised: 09/15/2008] [Accepted: 09/16/2008] [Indexed: 12/15/2022]
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Jeronimo A, Jeronimo CAD, Filho OAR, Sanada LS, Fazan VPS. A morphometric study on the longitudinal and lateral symmetry of the sural nerve in mature and aging female rats. Brain Res 2008; 1222:51-60. [DOI: 10.1016/j.brainres.2008.05.055] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Revised: 05/19/2008] [Accepted: 05/21/2008] [Indexed: 11/16/2022]
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