Pulsed focused ultrasound changes nerve conduction of earthworm giant axonal fibers
Sarah H. Yoo, Phillip Croce, Ryan W. Margolin, Stephanie D. Lee, Wonhye Lee
NeuroReport 2017, 28, 229-233 · 10.1097/wnr.0000000000000745
Abstract
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/cm spatial-peak temporal-average intensity (Ispta), and (III) sonication at 200 mW/cm Ispta. The sonication at 600 mW/cm 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/cm) 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.
Abstract via europepmc.
Exposures
Exposure 1: FUS to earthworm body (lateral and median giant axonal fibers)
Target: earthworm neurons — “lateral and median giant axonal fibers (LGF/MGF) of the earthworm”
Device: Ultran · The Ultran Group Ltd ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 210 | ✓✓✓ |
| Pulse duration (ms) | 1 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 20 | ✓✓✓ |
| Duty cycle (%) | 2pulse duration × PRF gives 2% | ✓✓✓ |
| Sonication duration (s) | 60 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Pressure, domain unspecified (kPa) | 945 | ✓✓✓⚑ |
| Isppa, domain unspecified (W/cm²) | 10, 30swept | ✓✓✓⚑ |
| Ispta, domain unspecified (W/cm²) | 0.2, 0.6swept | ✓✓✓ |
Sonication was administered over a tone burst duration of 1 ms at a pulse repetition frequency of 20 Hz (2% duty cycle), delivered continuously for 1 min (sessions f1-f4) at either 600 mW/cm2 or 200 mW/cm2 Ispta, following 5 baseline sessions (B1-B5) and preceding 5 post-sonication sessions (P1-P5); a control group received no sonication.
Flags from extraction
n_subjects— 53 worms were enrolled but 11 were excluded for technical problems; 42 worms (14 per condition) were analysed. n_subjects is recorded as the enrolled total (53) per the enrolled-vs-analysed rule.exposures[0].unspecified_domain.pressure_kpa— The 945 kPa rarefactional pressure is stated only for the 600 mW/cm2 Ispta condition; no corresponding pressure is given for the 200 mW/cm2 condition.exposures[0].unspecified_domain.isppa_w_cm2— The paper does not state whether the reported intensities were calibrated in free water or measured/estimated at the worm body; recorded as unspecified domain.sham_type— Condition III is described only as 'without providing actual sonication (i.e. control condition)'; whether the transducer/setup was otherwise identical (powered off) is not explicitly described, so sham mechanism is coded as other.