Conduction block of mammalian myelinated nerve by local cooling to 15–30°C after a brief heating

Zhang, Zhaocun; Lyon, Timothy D.; Kadow, Brian T.; Shen, Bing; Wang, Jicheng; Lee, Andy; Kang, Audry; Roppolo, James R.; Groat, William C. de; Tai, Changfeng

doi:10.1152/jn.00954.2015

Cited by 16 publications

(16 citation statements)

References 25 publications

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“…3 , 4 , 5 , 6 , 7 ), suggesting no neural damage was caused by the coil stimulation. For mammalian myelinated nerves in cats, heat blockage on action potentials happens at around 50 °C in 55 . Invertebrate axons operate between 0 and 40 °C 56 , and a more than 20 °C of local temperature increase was needed for thermal blockage of the unmyelinated squid giant axon 57 .…”

Section: Discussionmentioning

confidence: 99%

Somatic inhibition by microscopic magnetic stimulation

Barrett

2021

Sci Rep

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Electric currents can produce quick, reversible control of neural activity. Externally applied electric currents have been used in inhibiting certain ganglion cells in clinical practices. Via electromagnetic induction, a miniature-sized magnetic coil could provide focal stimulation to the ganglion neurons. Here we report that high-frequency stimulation with the miniature coil could reversibly block ganglion cell activity in marine mollusk Aplysia californica, regardless the firing frequency of the neurons, or concentration of potassium ions around the ganglion neurons. Presence of the ganglion sheath has minimal impact on the inhibitory effects of the coil. The inhibitory effect was local to the soma, and was sufficient in blocking the neuron’s functional output. Biophysical modeling confirmed that the miniature coil induced a sufficient electric field in the vicinity of the targeted soma. Using a multi-compartment model of Aplysia ganglion neuron, we found that the high-frequency magnetic stimuli altered the ion channel dynamics that were essential for the sustained firing of action potentials in the soma. Results from this study produces several critical insights to further developing the miniature coil technology for neural control by targeting ganglion cells. The miniature coil provides an interesting neural modulation strategy in clinical applications and laboratory research.

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Section: Discussionmentioning

confidence: 99%

Somatic inhibition by microscopic magnetic stimulation

Barrett

2021

Sci Rep

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“…Ten minutes after mepivacaine injection none of the horses responded to stimulation up to the safety cut‐off of 25 N, supporting MNT testing as a robust method for detecting limb desensitisation. Application of ice might be expected to cause at least partial desensitisation, 22 but this proved not to be the case, even as testing was performed immediately after the limb was iced for 10–15 minutes (common duration in endurance racing). Presumably any effect was transient and abated during application of the actuator, or was only limited to skin and not deeper structures.…”

Section: Discussionmentioning

confidence: 99%

Mechanical nociceptive thresholds in endurance horses

Schambourg¹,

Taylor²

2020

Veterinary Record

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BackgroundAlteration of limb sensitivity is forbidden in equine sports but difficult to enforce. We aimed to develop an objective field method to assess mechanical nociceptive threshold (MNT) in endurance horses.MethodsA remotely controlled pneumatic actuator (1 mm tip) was used to measure forelimb pastern MNT in 108 endurance horses.ResultsMedian (IQR) MNT at rest was 1.9 N (0.9–3.5). Icing had no significant effect on limb sensitivity. MNT measured at weekly intervals increased from week 1 (1.2 N (0.6–1.8)) to week 3 (1.9 N (1.2–2.8)) (P<0.05). In 17 horses without impaired sensitivity, MNT increased from 1.2 N (0.6–2.3) before to 2.4 N (1.2–5.2) after racing (P=0.0017). In desensitised horses, MNT after racing was higher (8 limbs—23.1 N (21.4 to >25)) than in horses without impaired sensitivity (42 limbs—2.2 N (1.2–4.3)) (P<0.0001). Desensitisation with mepivacaine increased MNT to above the safety cut-off (25 N) at 10 minutes; sensitivity return to baseline varied between individuals but was restored by 330 minutes. None of the horses became averse to the technique.ConclusionMNT was practical, non-traumatic, repeatable and well tolerated under field conditions in endurance horses. The technique differentiated postracing MNT in horses with normal sensitivity from those with impaired sensitivity.

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“…Heat block was first described by Hodgkin and Katz who noted that, at elevated temperatures, action potentials in the squid giant axons decreased in amplitude and increased in conduction velocity (CV), and that further increasing the temperature resulted in failure of the axons to conduct. Since this foundational article, thermally induced silencing of neural activity has been explored for a range of animal models and applications . Mechanistically, heat block is hypothesized to act through changes in voltage‐gated potassium channel dynamics .…”

Section: Introductionmentioning

confidence: 99%

Identifying the Role of Block Length in Neural Heat Block to Reduce Temperatures During Infrared Neural Inhibition

et al. 2019

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Background and Objectives The objective of this study is to assess the hypothesis that the length of axon heated, defined here as block length (BL), affects the temperature required for thermal inhibition of action potential propagation applied using laser heating. The presence of such a phenomenon has implications for how this technique, called infrared neural inhibition (INI), may be applied in a clinically safe manner since it suggests that temperatures required for therapy may be reduced through the proper spatial application of light. Here, we validate the presence of this phenomenon by assessing how the peak temperatures during INI are reduced when two different BLs are applied using irradiation from either one or two adjacent optical fibers. Study Design/Materials and Methods Assessment of the role of BL was carried out over two phases. First, a computational proof of concept was performed in the neural conduction simulation environment, NEURON, simulating the response of action potentials to increased temperatures applied at different full‐width at half‐maxima (FWHM) along axons. Second, ex vivo validation of these predictions was performed by measuring the radiant exposure, peak temperature rise, and FWHM of heat distributions associated with INI from one or two adjacent optical fibers. Electrophysiological assessment of radiant exposures at inhibition threshold were carried out in ex vivo Aplysia californica (sea slug) pleural abdominal nerves ( n = 6), an invertebrate with unmyelinated axons. Measurement of the maximum temperature rise required for induced heat block was performed in a water bath using a fine wire thermocouple. Finally, magnetic resonance thermometry (MRT) was performed on a nerve immersed in saline to assess the elevated temperature distribution at these radiant exposures. Results Computational modeling in NEURON provided a theoretical proof of concept that the BL is an important factor contributing to the peak temperature required during neural heat block, predicting a 11.7% reduction in temperature rise when the FWHM along an axon is increased by 42.9%. Experimental validation showed that, when using two adjacent fibers instead of one, a 38.5 ± 2.2% (mean ± standard error of the mean) reduction in radiant exposure per pulse per fiber threshold at the fiber output (P = 7.3E−6) is measured, resulting in a reduction in peak temperature rise under each fiber of 23.5 ± 2.1% ( P = 9.3E−5) and 15.0 ± 2.4% ( P = 1.4E−3) and an increase in the FWHM of heating by 37.7 ± 6.4% ( P = 1E−3), 68.4 ± 5.2% ( P = 2.4E−5), and 51.9 ± 9.9% ( P = 1.7E−3) in three MRT slices. Conclusions This study provides the first experimental evidence for a phenomenon during the heat block in which the temperature for inhibition is dependent on the BL. While more work is needed to further reduce the temperature during INI, the results highlight that spatial application of the temperature rise during INI must be considered. Optimized implementation of INI may leverage this cellular response to provide optical modul...

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Conduction block of mammalian myelinated nerve by local cooling to 15–30°C after a brief heating

Cited by 16 publications

References 25 publications

Somatic inhibition by microscopic magnetic stimulation

Somatic inhibition by microscopic magnetic stimulation

Mechanical nociceptive thresholds in endurance horses

Identifying the Role of Block Length in Neural Heat Block to Reduce Temperatures During Infrared Neural Inhibition

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