Ultrasound neuromodulation of cultured hippocampal neurons
Seoyoung Hwang, Sang Beom Jun
Biomedical Engineering Letters 2024 · 10.1007/s13534-023-00314-7
Abstract
Ultrasound is becoming an emerging and promising method for neuromodulation due to its advantage of noninvasiveness and its high spatial resolution. However, the underlying principles of ultrasound neuromodulation have not yet been elucidated. We have herein developed a new in vitro setup to study the ultrasonic neuromodulation, and examined various parameters of ultrasound to verify the effective conditions to evoke the neural activity. Neurons were stimulated with 0.5 MHz center frequency ultrasound, and the action potentials were recorded from rat hippocampal neural cells cultured on microelectrode arrays. As the intensity of ultrasound increased, the neuronal activity also increased. There was a notable and significant increase in both the spike rate and the number of bursts at 50% duty cycle, 1 kHz pulse repetition frequency, and the acoustic intensities of 7.6 W/cm 2 and 3.8 W/cm 2 in terms of spatial-peak pulse-average intensity and spatial-peak temporal-average intensity, respectively. In addition, the impact of ultrasonic neuromodulation was assessed in the presence of a gamma-aminobutyric acid A (GABA A ) receptor antagonist to exclude the effect of activated inhibitory neurons. Interestingly, it is noteworthy that the predominant neuromodulatory effects of ultrasound disappeared when the GABA A blocker was introduced, suggesting the potential of ultrasonic stimulation specifically targeting inhibitory neurons. The experimental setup proposed herein could serve as a useful tool for the clarification of the mechanisms underlying the electrophysiological effects of ultrasound.
Abstract via europepmc.
Exposures
Exposure 1: 0.5 MHz sonication of primary hippocampal neurons on MEA, intensity/duty cycle/duration/PRF sweeps
Target: cultured neurons — “primary hippocampal neurons cultured on microelectrode arrays”
Device: other named manufacturer · TKS Corp. (Busan, Republic of Korea) · custom-made water-immersion 10 x 10 mm square ultrasound transducer ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 500 | ✓✓✓ |
| Pulse duration (ms) | not reported | ⚑ |
| Pulse repetition frequency (Hz) | 10, 100, 500, 1,000, 2,000swept | ✓✓✓ |
| Duty cycle (%) | 10, 50, 90swept | ✓✓✓ |
| Sonication duration (s) | 20, 60, 120swept | ✓✓✓ |
| Free-field pressure (kPa) | 60, 240, 340, 490, 780swept | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | 0.11, 1.45, 3.26, 7.66, 17.38swept | ✓✓✓ |
| Free-field Ispta (W/cm²) | 0.06, 0.15, 0.72, 1.3, 1.63, 3.83, 8.7swept | ✓✓✓ |
| 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 |
One minute baseline recording, then ultrasound for 20 s (except in the duration experiment), then one minute of recording; each parameter varied with the others fixed at level 2 intensity (level 1-5 in the intensity sweep), 50% duty cycle, 1 kHz PRF and 20 s.
Flags from extraction
n_subjects— Only a range of MEAs per parameter is stated (3-6); no total number of cultures or animals. Recorded as the range.exposures[0].unspecified_domain.pressure_kpa— Pressures were measured by hydrophone at the MEA surface through Parafilm in culture medium, 3 mm from the transducer, but the paper never says free field or water, so placed in unspecified_domain.exposures[0].unspecified_domain.ispta_w_cm2— Table 1 gives ISPTA at DC 10, 50 and 90 % for five levels; the list records the DC = 50 % column (the intensity sweep used 50 % DC). Other columns not recorded.exposures[0].unspecified_domain.isppa_w_cm2— Table 1 values; ISPPA calculated by the authors from hydrophone pressure.exposures[0].timing.pulse_duration_ms— Pulse duration never stated numerically, only 50 % DC at 1 kHz PRF as the base condition; not computed.exposures[0].timing.protocol_description— Intensity, DC, duration and PRF swept one at a time with others fixed; Table 1 mechanical index for level 3 (0.14) looks inconsistent with the other rows (possible typo), not recorded.exposures[0].device.family— Transducer described as custom-made by TKS Corp.; classed other_manufacturer.