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Abstract

Background
Transcranial ultrasound stimulation can acutely modulate brain activity, but the lasting effects on neurons are unknown.
Objective
To assess the excitability profile of neurons in the hours following transient ultrasound stimulation.
Methods
Primary rat cortical neurons were stimulated with a 40 s, 200 kHz pulsed ultrasound stimulation or sham-stimulation. Intrinsic firing properties were investigated through whole-cell patch-clamp recording by evoking action potentials in response to somatic current injection. Recordings were taken at set timepoints following ultrasound stimulation: 0–2 h, 6–8 h, 12–14 h and 24–26 h. Transmission electron microscopy was used to assess synaptic ultrastructure at the same timepoints.
Results
In the 0–2 h window, neurons stimulated with ultrasound displayed an increase in the mean frequency of evoked action potentials of 32% above control cell levels (p = 0.023). After 4–6 h this increase was measured as 44% (p = 0.0043). By 12–14 h this effect was eliminated and remained absent 24–26 h post-stimulation. These changes to action potential firing occurred in conjunction with statistically significant differences between control and ultrasound-stimulated neurons in action potential half-width, depolarisation rate, and repolarisation rate, that were similarly eliminated by 24 h following stimulation. These effects occurred in the absence of alterations to intrinsic membrane properties or synaptic ultrastructure.
Conclusion
We report that stimulating neurons with 40 s of ultrasound enhances their excitability for up to 8 h in conjunction with modifications to action potential kinetics. This occurs in the absence of major ultrastructural change or modification of intrinsic membrane properties. These results can inform the application of transcranial ultrasound in experimental and therapeutic settings.
Original languageEnglish
Pages (from-to)217-225
Number of pages9
JournalBrain Stimulation
Volume14
Issue number2
Early online date12 Jan 2021
DOIs
Publication statusPublished - 15 Jan 2021

Bibliographical note

Funding Information:
The authors gratefully acknowledge the Wolfson Bioimaging Facility for their support and assistance with electron microscopy. UC7 Ultramicrotome was made available by BBSRC Alert 13 capital grant ( BB/L014181/1 ). This work was supported in part by grant MR/N0137941/1 for the GW4 BIOMED DTP, awarded to the Universities of Bath, Bristol, Cardiff and Exeter from the Medical Research Council (MRC, UKRI).

Publisher Copyright:
© 2021

Keywords

  • Ultrasound stimulation
  • Neuromodulation
  • Intrinsic excitability
  • Primary neuron
  • Whole-cell patch clamp
  • Electron microscopy

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