Ultrasound Activation of Mechanosensory Ion Channels in Caenorhabditis Elegans

Wei Zhou, Xinhui Wang, Kaiyue Wang, Umar Farooq, Lijun Kang, Lili Niu, Long Meng

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2022 · 10.1109/tuffc.2021.3120750

invertebratehealthybehaviourcellular imaging

Abstract

Ultrasound is capable of noninvasive transcranial focusing and activating the targeted neurons in brain regions, receiving increasing attention. Ion channel, acting as a nano-ionic switch, enables to modulate the ion flow across cellular membranes and it is of importance to control the firing frequency of a neuron. In this article, we demonstrate the behavioral response of Caenorhabditis elegans (C. elegans) in response to ultrasound stimulation mediated by the activation of mechanical sensitive MEC-4 and MEC-6 ion channels. By specific mutation of MEC-4 and MEC-6 ion channels, mutant worms show a significant decrease in the percentage of reversal behavior (30% ± 10.5% and 10% ± 6.9%, respectively), compared with wild type (85% ± 8.2%). Furthermore, ALM and PLM neurons expressing MEC-4 and MEC-6 ion channels could be evoked directly by ultrasound stimulation, indicating MEC-4 and MEC-6 may pave a new way for sonogenetics.

Abstract via europepmc.

Speciesnematode (Caenorhabditis elegans)

Subjects20, 20, 20, 20, 20, 20swept animals

Sessions per subjectnot reported

Randomisednot reported

Blindingnot reported

Sham / controlnone

Auditory controlnot reported

Readout timingonline

Anaesthesianot reported

Readoutsbehaviour, cellular imaging — reversal behaviour (proportion reversing); GCaMP5.0 calcium imaging of ALM and PLM neurons

Direction of effectexcitatoryUltrasound evoked reversal behaviour in 85% of wild-type worms, reduced in mec-4 (30%) and mec-6 (10%) mutants; ALM and PLM neurons showed increased GCaMP5.0 fluorescence.

Adverse eventsnot reportedCavitation was checked by LDV frequency scan (no harmonics or wideband noise); temperature rise described as small but not quantified.

Exposures

Exposure 1: 27.4 MHz SAW device, single 6.4 ms pulse, C. elegans on agar

Target: c elegans neurons — “ALM and PLM neurons expressing MEC-4 and MEC-6 ion channels”
Device: custom-built · interdigital transducer (IDT) surface acoustic wave device on 128 deg YX-LiNbO3 substrate

Pulse timing
Waveform	continuous
Fundamental frequency (kHz)	27,400	✓✓✓
Pulse duration (ms)	not applicable
Pulse repetition frequency (Hz)	not applicable
Duty cycle (%)	not applicable
Sonication duration (s)	0.0064	✓✓✓⚑

Pressure and intensity, by domain
Free-field pressure (kPa)	3,000	✓✓✓
Free-field Isppa (W/cm²)	not reported
Free-field Ispta (W/cm²)	not reported
In-situ estimate	not applicable
In-situ pressure (kPa)	not applicable
In-situ Isppa (W/cm²)	not applicable
In-situ Ispta (W/cm²)	not applicable

Protocol, in the paper’s words

Worms moved freely on the agar surface for 5 min and were then stimulated with a single-pulse ultrasound (input electronic power: 5 W, pulse duration: 6.4 ms). Twenty worms per group.

Consistency checks: f0 out of range.

Flags from extraction

n_subjects — Only group sizes given: 20 per behavioural group (6 genotypes), ALM n=9, PLM n=8; no total. The 20 appears in the figure legend as spaced digits.
exposures[0].unspecified_domain.pressure_kpa — Approximately 3 MPa calculated from LDV vibration amplitude on the agar surface at 5 W input; the paper does not label the domain.
exposures[0].timing.sonication_duration_s — Single 6.4 ms pulse treated as one continuous burst; 6.4 ms is stated as 'pulse duration'.
exposures[0].device.family — IDT fabricated by MEMS technology; builder not named, so recorded as custom_built.