Ultrasound modulates neuronal potassium currents via ionotropic glutamate receptors
Benjamin Clennell, Tom G.J. Steward, Kaliya Hanman, Tom Needham, Janette Benachour, Mark Jepson, Meg Elley, Nathan Halford, Kate Heesom, Eunju Shin, Elek Molnár, Bruce W. Drinkwater, Daniel J. Whitcomb
Brain Stimulation 2023, 16, 540-552 · 10.1016/j.brs.2023.01.1674
Abstract
Background Focused ultrasound stimulation (FUS) has the potential to provide non-invasive neuromodulation of deep brain regions with unparalleled spatial precision. However, the cellular and molecular consequences of ultrasound stimulation on neurons remains poorly understood. We previously reported that ultrasound stimulation induces increases in neuronal excitability that persist for hours following stimulation in vitro. In the present study we sought to further elucidate the molecular mechanisms by which ultrasound regulates neuronal excitability and synaptic function. Objectives To determine the effect of ultrasound stimulation on voltage-gated ion channel function and synaptic plasticity. Methods Primary rat cortical neurons were exposed to a 40 s, 200 kHz pulsed ultrasound stimulus or sham-stimulus. Whole-cell patch clamp electrophysiology, quantitative proteomics and high-resolution confocal microscopy were employed to determine the effects of ultrasound stimulation on molecular regulators of neuronal excitability and synaptic function. Results We find that ultrasound exposure elicits sustained but reversible increases in whole-cell potassium currents. In addition, we find that ultrasound exposure activates synaptic signalling cascades that result in marked increases in excitatory synaptic transmission. Finally, we demonstrate the requirement of ionotropic glutamate receptor (AMPAR/NMDAR) activation for ultrasound-induced modulation of neuronal potassium currents. Conclusion These results suggest specific patterns of pulsed ultrasound can induce contemporaneous enhancement of both neuronal excitability and synaptic function, with implications for the application of FUS in experimental and therapeutic settings. Further study is now required to deduce the precise molecular mechanisms through which these changes occur.
Abstract via europepmc.
Exposures
Exposure 1: Pulsed ultrasound exposure of primary cortical neuron cultures
Target: cultured neurons — “primary rat cortical neuron cultures”
Device: other named manufacturer · Farnell · MCUSD19A200B11RS ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 200 | ✓✓✓ |
| Pulse duration (ms) | 100 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 5 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 50% | ⚑ |
| Sonication duration (s) | 40 | ✓✓✓ |
| Free-field pressure (kPa) | 120 | ✓✓✓ |
|---|---|---|
| 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 | |
| Pressure, domain unspecified (kPa) | 200, 390swept | ✓?⚑ |
Neurons submerged in HBS were exposed once to a 200 kHz sinusoidal ultrasound stimulus (50 V peak-to-peak transducer excitation) delivered in 100 ms pulses with 100 ms pulse intervals for 40 s total (5 Hz pulse repetition frequency), or to a sham procedure (equipment powered on, no excitation signal, so no ultrasound generated). Finite-element modelling indicated a standing wave increased pressure at the coverslip 2- to 4-fold relative to free field as the transducer-to-coverslip standoff was varied between 4.5 and 5.5 mm.
Flags from extraction
n_subjects— Paper reports animal/neuron/sample counts per individual assay (e.g., 'Neuronal cultures derived from five animals' for proteomics; neuron counts such as N=23/21 given only in figure legends) but never a single total number of cultures/animals used across the whole study.exposures[0].unspecified_domain.pressure_kpa— The 0.2-0.39 MPa range is the modelled pressure actually reached at the coverslip/neurons due to a standing-wave effect from the acoustically hard coverslip; the paper distinguishes this from the 0.12 MPa 'free-field' pressure but does not call the at-cell value in-situ (no tissue/skull path in this in vitro dish preparation), so it is recorded as unspecified_domain rather than assumed equal to free field.exposures[0].timing.duty_cycle_pct— 100 ms pulses with 100 ms intervals implies a 50% duty cycle, but the paper does not itself state a duty-cycle percentage, so this was left not_reported rather than computed.