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Pulsed focused ultrasound changes nerve conduction of earthworm giant axonal fibers

Yoo, Sarah H.; Croce, Phillip; Margolin, Ryan W.; Lee, Stephanie D.; Lee, Wonhye

doi: 10.1097/WNR.0000000000000745
Degeneration and Repair

This study examined the effects of pulsed focused ultrasound (FUS) in disrupting nerve conduction. FUS operating at a 210 kHz fundamental frequency was administered to the medial and lateral giant axonal nerve fibers of earthworms in a burst of pulses (1 ms tone burst duration, 20 Hz pulse repetition frequency). The magnitude and latencies of the nerve potentials induced by electrical stimulation were measured under three experimental conditions – (I) no sonication, (II) sonication at 600 mW/cm2 spatial-peak temporal-average intensity (Ispta), and (III) sonication at 200 mW/cm2 Ispta. The sonication at 600 mW/cm2 temporarily decreased the magnitude of the action potential peak (~16%), whereas the baseline peak level was quickly restored in postsonication sessions. Sonication administered at a lower intensity (i.e. 200 mW/cm2) did not alter the peak magnitude. The sonication did not alter the nerve conduction velocity. The acoustic intensities used in the experiment did not increase the temperature of the sonicated tissue. The results indicate that axonal neurotransmission can be disrupted temporarily by the application of pulsed FUS, suggesting its potential utility in modulating the functional connectivity established by white matter tracts in the brain.

aNoble and Greenough School, Dedham

bDepartment of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA

Correspondence to Wonhye Lee, PhD, Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA Tel: +1 617 732 9464; fax: +1 617 732 9185; e-mail: wonhye@bwh.harvard.edu

Received December 30, 2016

Accepted January 11, 2017

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