Image-guided focused ultrasound modulates electrically evoked motor neuronal activity in the mouse peripheral nervous system in vivo

摘要

Objective. Focused ultrasound (FUS) has recently been demonstrated capable of exciting motorneuronal activity. However, comprehensive understanding of elucidated excitatory and inhibitoryeffects is required to better assess FUS-mediated modulation. In this study, we demonstrate thatimage-guided FUS can selectively modulate motor neuron activity in the mouse sciatic nerve invivo and attribute motor responses to thermal effects. Approach. FUS was applied on the sciaticnerve of anesthetized mice in vivo through the intact skin and muscle using ultrasound imagingfor targeting. Both excitatory and inhibitory effects were recorded using electromyography (EMG)along with muscle response of the hind limb. The effects of FUS modulation versus heating byinvasive alternative heating source (AHS) on electrically evoked EMG responses in the sciatic nervein vivo were also investigated. The safety and reversibility of the technique were validated usinghistology and EMG recovery. Main results. The FUS was capable of eliciting motor neuronal activitycomparable to electrical stimulation ES, and facilitating motor neuronal response on electricallyevoked potentials with temperature elevation up to 11.5 ℃ ± 0.3 ℃ (PRF ⩽ 40 Hz). On the otherhand, FUS-induced temperature elevations above 15.1 ℃ ± 1.6 ℃ (PRF ⩾ 100 Hz) resulted in thesuppression of electrically-evoked motor neuronal activity along with a decrease in EMG latencyand area under the curve (AUC), which was validated against the invasive AHS with temperatureelevation of 18.1 ℃ ± 8.5 ℃. Histological findings along with EMG responses after FUS modulationdemonstrated a reversible or irreversible modulation. Significance. The findings reported hereinindicate that image-guided FUS (PRF ⩽ 100 Hz) induces safe and controllable modulation ofinvoluntarily evoked motor neuron activity in vivo.