The effects of low intensity focused ultrasound on neuronal activity in pain processing regions in a rodent model of common peroneal nerve injury
Jonathan Bao, Kanakaharini Byraju, Vraj J. Patel, Abigail Hellman, Paul Neubauer, Clif Burdette, Emily Rafferty, Yunseo Linda Park, Rachel Trowbridge, Damian S. Shin, Julie G. Pilitsis
Neuroscience Letters 2022, 789, 136882 · 10.1016/j.neulet.2022.136882
Abstract
Background Non-invasive, external low intensity focused ultrasound (liFUS) offers promise for treating neuropathic pain when applied to the dorsal root ganglion (DRG). Objective We examine how external liFUS treatment applied to the L5 DRG affects neuronal changes in single-unit activity from the primary somatosensory cortex (SI) and anterior cingulate cortex (ACC) in a common peroneal nerve injury (CPNI) rodent model. Methods Male Sprague Dawley rats were divided into two cohorts: CPNI liFUS and CPNI sham liFUS. Baseline single-unit activity (SUA) recordings were taken 20 min prior to treatment and for 4 h post treatment in 20 min intervals, then analyzed for frequency and compared to baseline. Recordings from the SI and ACC were separated into pyramidal and interneurons based on waveform and principal component analysis. Results Following CPNI surgery, all rats (n = 30) displayed a significant increase in mechanical sensitivity. In CPNI liFUS rats, there was a significant increase in pyramidal neuron spike frequency in the SI region compared to the CPNI sham liFUS animals beginning at 120 min following liFUS treatment (p Conclusion We demonstrate that liFUS changed neuronal spiking in the SI and ACC regions 80 and 120 min after treatment, respectively, which may in part correlate with improved sensory thresholds. This may represent a mechanism of action how liFUS attenuates neuropathic pain. Understanding the impact of liFUS on pain circuits will help advance the use of liFUS as a non-invasive neuromodulation option.
Abstract via europepmc.
Exposures
Exposure 1: liFUS to left L5 DRG
Target: dorsal root ganglion — “left L5 dorsal root ganglion (DRG)”
Device: other named manufacturer · Acoustic MedSystems, Inc. ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 11,000 | ✓✓✓ |
| Pulse duration (ms) | 13 | ✓✓✓⚑ |
| Pulse repetition frequency (Hz) | 38 | ✓✓✓ |
| Duty cycle (%) | 50pulse duration × PRF gives 49.4% | ✓✓✓ |
| Sonication duration (s) | 180 | ✓✓✓ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Isppa, domain unspecified (W/cm²) | 20 | ✓✓✓⚑ |
Treatment occurred for 3 min at 20 W/cm2 and an ultrasonic frequency of 11 MHz pulsed at 38 Hz with 50% duty cycling, a period of 90 µs, and a pulse width of 13 ms. The probe contains 2 angled piezo transducers which focus treatment on a region at a depth of 5 mm.
Flags from extraction
n_subjects— Paper states a combined CPNI total (n=30, including both liFUS and sham liFUS animals) and gives neuron/unit counts per cohort in figure legends, but does not state the number of animals specifically receiving active liFUS.sham_type— The paper refers repeatedly to a 'CPNI sham liFUS' condition but never describes what the sham liFUS procedure entailed (e.g., device off, blocked, or aimed away), so mechanism is unknown.exposures[0].timing.pulse_duration_ms— Text states 'a period of 90 µs' alongside a 38 Hz PRF (implied period ~26.3 ms) and 13 ms pulse width; the 90 µs value is inconsistent with the other stated parameters (possible typo/unit error in source) and was not used for any field.exposures[0].unspecified_domain.isppa_w_cm2— Paper states '20 W/cm2' without specifying whether this is Isppa or Ispta, or the measurement domain (free field vs. at target).