Frequency dependent, reversible focused ultrasound suppression of evoked potentials in the reflex arc in an...

To investigate the potential for noninvasive low frequency, low intensity ultrasound to suppress evoked potentials in the reflex arc neural pathway in anesthetized animal.

Single unit Electromyographic recordings of gastrocnemius muscle activity were obtained in response to electrical activation of the sciatic nerve, in anesthetized animal, with and without US stimulation. Reflex related potentials were evoked via electrical stimulation and low-intensity, low-frequency ultrasound was applied to the sciatic nerve. Electromyogram (EMG) was recorded from the gastrocnemius muscle and amplitude and area under the curve were analyzed to determine the effect of ultrasound stimulation on potentials in the reflex arc. Thermal imaging was used to assess thermal effects of US stimulation and immunohistochemical was performed post-US stimulation assess potential damage to the nerve.

Our results show a drop in electromyogram amplitudes as high as 20%, and a drop in areas under the curve as high as 23%, with greater effects at lower frequencies (200 kHz) and lower acoustic intensities. The suppression of EMG scales with the magnitude of the electrical stimuli. Also, our results demonstrated transient reversibility of US suppression and our experiments eliminated thermal effects and mechanical and thermal damage.

The non-invasiveness of US stimulation and its inhibitory and reversible effects emphasize the potential of US as a therapeutic modality and clinical tool for suppression of neural potentials in the reflex arc such as the case for pain treatments. The study lays the ground for potential applications of US stimulation in pain treatment.