Trans-spinal direct current stimulation modulates motor cortex-induced muscle contraction in mice

Abstract

The present study investigated the effect of trans-spinal direct current (tsDC) on the firing rate, pattern, and amplitude of spontaneous activity of the tibial nerve and on the magnitude of cortically elicited triceps surae (TS) muscle contractions. The effect of combined tsDC and repetitive cortical electrical stimulation (rCES) on the amplitude of cortically elicited TS twitches was also investigated. Stimulation was applied by two disk electrodes (0.79 cm(2)): one was located subcutaneously over the vertebral column (T(10)-L(1)) and was used to deliver anodal DC (a-tsDC) or cathodal DC (c-tsDC) (density range: ± 0.64 to ± 38.2 A/m(2)), whereas the other was located subcutaneously on the lateral aspect of the abdomen and served as a reference. While the application of a-tsDC significantly increased the spike frequency and amplitude of spontaneous discharges compared with c-tsDC, c-tsDC made the spontaneous discharges more rhythmic. Cortically elicited TS twitches were depressed during a-tsDC and potentiated after termination. Conversely, cortically elicited TS twitches were enhanced during c-tsDC and depressed after termination. While combined a-tsDC and rCES produced similar effects as a-tsDC alone, combined c-tsDC and rCES showed the greatest increase in cortically elicited TS twitches. tsDC appears to be a powerful neurostimulation tool that can differentially modulate spinal cord excitability and corticospinal transmission.

Trans-Spinal Direct Current Stimulation Alters Muscle Tone in Mice with and without Spinal Cord Injury with Spasticity

“…In general, following spinal cord injury, increased excitation and reduced inhibition of the mechanisms controlling motoneurons causes abnormal generation of force (Roy and Edgerton, 2012). We previously showed that dorsal surface anodal stimulation of the spinal cord decreases spinal excitability, while cathodal stimulation increases excitability (Ahmed, 2011). This agrees with previous studies, despite differences in location of the return electrode (Fuortes, 1954;Eccles et al, 1962).…”

“…The general procedure has been used previously by our laboratory (Ahmed, 2011(Ahmed, , 2013aAhmed and Wieraszko, 2012), and the experimental setup is shown in Figure 1A. Animals were anesthetized using ketamine/xylazine (90/10 mg/kg, i.p.).…”

Effects of Cathodal Trans-Spinal Direct Current Stimulation on Mouse Spinal Network and Complex Multijoint Movements

“…Plantarflexion movements were increased in amplitude, duration, and slope, but not latency. This was most likely due to increased TS muscle force produced by c-tsDC stimulation (Ahmed, 2011;Ahmed and Wieraszko, 2012). Dorsiflexion movements showed decreased latency and increased amplitude and slope, but no change in duration.…”

“…Trans-spinal direct current (tsDC) stimulation is a neuromodulatory technique that causes immediate and long-term changes in spinal cord excitability (Aguilar et al, 2011;Ahmed, 2011Ahmed, , 2013Cogiamanian et al, 2011;Truini et al, 2011;Ahmed and Wieraszko, 2012;Cogiamanian et al, 2012;Lamy et al, 2012;Lamy and Boakye, 2013). The overarching goal of tsDC stimulation is to restore function that has been lost due to spinal cord or brain injuries.…”

“…When applied on the dorsum of the spinal cord, c-tsDC stimulation significantly enhances spinal excitability (Alanis, 1953;Eccles et al, 1962;Aguilar et al, 2011;Ahmed, 2011). This spinal facilitation can be exploited to restore motor or sensory function after brain or spinal cord injury.…”