Focused ultrasound excites cortical neurons via mechanosensitive calcium accumulation and ion channel amplification
Sangjin Yoo, David R. Mittelstein, Robert C. Hurt, Jerome Lacroix, Mikhail G. Shapiro
Nature Communications 2022, 13 · 10.1038/s41467-022-28040-1
Abstract
Ultrasonic neuromodulation has the unique potential to provide non-invasive control of neural activity in deep brain regions with high spatial precision and without chemical or genetic modification. However, the biomolecular and cellular mechanisms by which focused ultrasound excites mammalian neurons have remained unclear, posing significant challenges for the use of this technology in research and potential clinical applications. Here, we show that focused ultrasound excites primary murine cortical neurons in culture through a primarily mechanical mechanism mediated by specific calcium-selective mechanosensitive ion channels. The activation of these channels results in a gradual build-up of calcium, which is amplified by calcium- and voltage-gated channels, generating a burst firing response. Cavitation, temperature changes, large-scale deformation, and synaptic transmission are not required for this excitation to occur. Pharmacological and genetic inhibition of specific ion channels leads to reduced responses to ultrasound, while over-expressing these channels results in stronger ultrasonic stimulation. These findings provide a mechanistic explanation for the effect of ultrasound on neurons to facilitate the further development of ultrasonic neuromodulation and sonogenetics as tools for neuroscience research.
Abstract via europepmc.
Exposures
Exposure 1: Ultrasound stimulation of cultured primary cortical neurons
Target: cultured neurons — “primary cortical neurons in culture”
Device: other named manufacturer · Benthowave Instrument INC. Canada · BII-7654/300IM ✓
| Waveform | continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 300 | ✓✓✓⚑ |
| Pulse duration (ms) | not applicable | |
| Pulse repetition frequency (Hz) | not applicable | |
| Duty cycle (%) | not applicable | |
| Sonication duration (s) | 0, 0.5swept | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | 0, 15swept | ✓✓✓⚑ |
| 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 |
Cultured cortical neurons on an acoustically transparent Mylar film were stimulated with continuous-wave ultrasound across a range of pulse intensities (0-15 W/cm2) and pulse durations (0-500 ms, CW), inter-pulse interval fixed at 20 s; subsequent experiments used 15 W/cm2 and 500 ms CW. A 670 kHz transducer and pulsed-wave stimulation (1 kHz and 1.5 kHz PRF) were also tested for comparison with no substantial difference in response amplitude or onset delay from the 300 kHz CW condition.
Flags from extraction
n_subjects— Reported as independent-experiment replicate counts (n=3-7 dishes) that vary across dozens of separate sub-experiments; no aggregate total of stimulated cultures is given.n_sessions_per_subject— Each dish received many repeated ultrasound pulses at randomized intensities/durations (inter-pulse interval 20 s); no discrete 'session' count per dish is stated.exposures[0].fundamental_frequency_khz— A second, less-characterized frequency (670 kHz, different transducer) was also tested with the same general configuration and found not to differ from 300 kHz; recorded only as a note in protocol_description rather than as a list value because other parameters/device were not identically documented for it.exposures[0].free_field.isppa_w_cm2— Domain classified as free-field because neurons were stimulated in a water tank with no skull/tissue path; the paper reports generic 'acoustic intensity' rather than explicitly labelling it Isppa or Ispta.