Ultrasound Stimulations Induce Prolonged Depolarization and Fast Action Potentials in Leech Neurons
Francesca Dedola, Francesco Paolo Ulloa Severino, Nicolo Meneghetti, Theo Lemaire, Andrea Cafarelli, Leonardo Ricotti, Arianna Menciassi, Annarita Cutrone, Alberto Mazzoni, Silvestro Micera
IEEE Open Journal of Engineering in Medicine and Biology 2020 · 10.1109/ojemb.2019.2963474
Abstract
Objective: Ultrasound (US) stimulation carries the promise of a selective, reversible, and non-invasive modulation of neural activity without the need for genetic manipulation of neural structures. However, the mechanisms of US-induced generation of action potentials (APs) are still unclear. Methods: Here we address this issue by analyzing intracellularly recorded responses of leech nociceptive neurons to controlled delivery of US. Results: US induced a depolarization linearly accumulating in time and outlasting the duration of the stimulation. Spiking activity was reliably induced for an optimal US intensity range. Moreover, we found that APs induced by US differ in smaller amplitude and faster repolarization from those induced by electrical stimulation in the same cell but display the same repolarization rate. Conclusions: These results shed light on the mechanism by which spikes are induced by US and pave the way for designing more efficient US stimulation patterns.
Abstract via europepmc.
Exposures
Exposure 1: Leech ganglion nociceptive (N) and pressure (P) mechanosensory neurons
Target: leech neurons — “leech ganglion nociceptive (N) and pressure (P) mechanosensory neurons”
Device: other named manufacturer · Precision Acoustics LTD ✓
| Waveform | pulsed, continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 490 | ✓✓✓ |
| Pulse duration (ms) | 5, 50, 100swept | ✓✓✓ |
| Pulse repetition frequency (Hz) | 10 | ✓✓✓ |
| Duty cycle (%) | 5, 50, 100swept | ✓✓✓⚑ |
| Sonication duration (s) | 0.3 | ✓✓✓ |
| Free-field pressure (kPa) | 8, 12, 16, 20swept | ✓✓✓⚑ |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | 0.0002, 0.027swept | ✓✓✓ |
| 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 |
Sinusoidal tone bursts at 490 kHz were delivered at a pulse repetition frequency of 10 Hz (pulse repetition period 100 ms) for a total stimulus duration of 300 ms per stimulation window; duty cycle was fixed at 5%, 50% or 100% (T-on of 5, 50 or 100 ms respectively within the 100-ms period; 100% DC is continuous, i.e. no off-time). Each 300-ms stimulation was repeated 3 times during a recording session with an inter-stimulation interval of 20-30 s; electrical pulses were used to generate a single spike in N cells before and after each US window to confirm cell health.
Flags from extraction
exposures[0].free_field.pressure_kpa— the Methods section (Ultrasound Calibration) states the transducer was 'characterized in free field conditions', but the Results text separately states the root-mean-square pressure was 'evaluated in the Petri dish containing the pinned ganglia'; domain is therefore somewhat ambiguous between free-field water-tank calibration and an at-target (in-dish) measurement, recorded here as free_field per the explicit 'free field conditions' statement.exposures[0].timing.duty_cycle_pct— duty cycle of 100% corresponds to continuous-wave stimulation (T-on = full 100-ms period, no off-time); merged into a single exposure with the pulsed 5% and 50% duty-cycle conditions as a parameter sweep at the same target and frequency.n_subjects— 47 N cells and 23 P cells were both stimulated with ultrasound (70 total); the paper does not separately break down how many leeches these cells came from.anaesthesia— leeches were kept at 5C and dissected in chilled Ringer's solution, but the paper does not explicitly describe this as anaesthesia; the isolated ganglion preparation itself was not anaesthetised during ultrasound delivery.