Synaptic Effect of Aδ-Fibers by Pulse-Train Electrical Stimulation

Abstract

Electrical stimulation of specific small fibers (Aδ- and C-fibers) is used in basic studies on nociception and neuropathic pain and to diagnose neuropathies. For selective stimulation of small fibers, the optimal stimulation waveform parameters are an important aspect together with the study of electrode design. However, determining an optimal stimulation condition is challenging, as it requires the characterization of the response of the small fibers to electrical stimulation. The perception thresholds are generally characterized using single-pulse stimulation based on the strength-duration curve. However, this does not account for the temporal effects of the different waveforms used in practical applications. In this study, we designed an experiment to characterize the effects of multiple pulse stimulation and proposed a computational model that considers electrostimulation of fibers and synaptic effects in a multiscale model. The measurements of perception thresholds showed that the pulse dependency of the threshold was an exponential decay with a maximum reduction of 55%. In addition, the frequency dependence of the threshold showed a U-shaped response with a reduction of 25% at 30 Hz. Moreover, the computational model explained the synaptic effects, which were also confirmed by evoked potential recordings. This study further characterized the activation of small fibers and clarified the synaptic effects, demonstrating the importance of waveform selection.

Selective stimulation of nociceptive small fibers during intraepidermal electrical stimulation: Experiment and computational analysis

“…(Valentin, 2002;Koster et al, 2012). The conductivity values and dimensions [1.54 mm (depth) × 1.65 mm × 1.65 mm] of the skin were the same as those reported in our previous studies (Tanaka et al, 2021b). In detail, the conductivity of the stratum corneum was selected as 2 × 10 −4 [S/m] at 2.1 kHz based on (Gabriel et al, 1996).…”

“…In our previous study (Tanaka et al, 2021a), we proposed a new synaptic model. The model is briefly summarized.…”

“…To overcome the above-mentioned difficulty, the first approach was to perform electrical analysis in a microscopic skin (volume conductor) model to evaluate the induced electric field intensity in IES (Mørch et al, 2011;Frahm et al, 2013;Motogi et al, 2016). A multiscale model, which integrates the computational model of the biophysical nerve model with electrical analysis, can be used to estimate the stimulation threshold for a single-pulse stimulation with different durations in Aδ-fiber activation (Hennings et al, 2017;Poulsen et al, 2020;Hirata et al, 2021;Tanaka et al, 2021b). To estimate measured perception thresholds with multiple pulse stimulation (Lilly et al, 1952;Gomez-Tames et al, 2019), we proposed a novel multiscale model integrated with the synaptic effect (Tanaka et al, 2021a).…”

“…A multiscale model, which integrates the computational model of the biophysical nerve model with electrical analysis, can be used to estimate the stimulation threshold for a single-pulse stimulation with different durations in Aδ-fiber activation (Hennings et al, 2017;Poulsen et al, 2020;Hirata et al, 2021;Tanaka et al, 2021b). To estimate measured perception thresholds with multiple pulse stimulation (Lilly et al, 1952;Gomez-Tames et al, 2019), we proposed a novel multiscale model integrated with the synaptic effect (Tanaka et al, 2021a). The model describes how the perception thresholds of Aδ-fiber vary for different numbers of pulses.…”

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“…Наявні відомості щодо лікування головного болю за допомогою електротерапії. Показана гемодинамічна відповідь у верхніх і нижніх кінцівках на нейром'язову електростимуляцію, що викликає м'язові скорочення і таким чином впливає на сенсомоторну реакцію в цілому, а також синаптичний ефект Aδ-білків при стимуляції імпульсним електричним струмом (Tanaka et al, 2021).…”