Stimulation of dorsal root ganglion with low-intensity focused ultrasound ameliorates pain responses through the GABA inhibitory pathway
Ya-Tin Lin, Ko-Ting Chen, Chun-Chun Hsu, Hao-Li Liu, Yu-Ting Jiang, Chieh-Wen Ho, Jin-Chung Chen, Hui-Yun Li, Chi-Chang Weng, Po-Hung Hsu
Life Sciences 2025, 361, 123323 · 10.1016/j.lfs.2024.123323
Abstract
Aims Chronic pain is a critical public health issue that severely impacts quality of life and poses significant treatment challenges, particularly due to the risk of adverse effects associated with pharmacological therapies. The search for effective non-invasive treatment alternatives has become increasingly relevant. Low-intensity focused ultrasound (LIFU) has been identified as an effective non-invasive strategy for pain management, although the underlying mechanism remains unclear. This study aimed to evaluate the analgesic effects and cellular mechanisms of LIFU-induced neuromodulation targeted on dorsal root ganglia (DRG) in both inflammatory and neuropathic pain models. Materials and methods The study adopted in vivo complete Freund's adjuvant-induced inflammatory pain and chronic constriction injury-induced neuropathic pain rat models, along with ex vivo DRG primary cultures. Key findings The application of LIFU resulted in a time-dependent analgesic response in both pain models. The neurophysiological analyses revealed that LIFU activated GABAergic neurons and deactivated CGRP-expressing neurons triggered by noxious stimuli. The analgesic effects of LIFU and the LIFU-deactivated CGRP-containing neurons were reversed by injecting GABA antagonist to the L5 DRG, confirming the mediation of these effects through the GABAergic pathways. Ex vivo LIFU stimulation of DRG resulted in increased GABA release and decreased capsaicin-triggered CGRP cascades, further supporting in vivo findings. Significance We demonstrate, for the first time, that LIFU modulates the GABA-CGRP pathways in the peripheral sensory neurons to alleviate pain, which underscores the importance of GABAergic systems in LIFU-induced analgesia. Our results reveal potential clinical applications of FUS for pain management through the peripheral nervous system.
Abstract via europepmc.
Exposures
Exposure 1: LIFU/FUS stimulation of the dorsal root ganglion (DRG) in CFA inflammatory and CCI neuropathic pain models (in vivo), and DRG primary cultures (ex vivo)
Target: dorsal root ganglion — “dorsal root ganglia (DRG), lumbar L3-L6”
Device: IGT / Imasonic · Imasonic SAS, France ✓
| Waveform | pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 400 | ✓✓✓ |
| Pulse duration (ms) | 0.625 | ✓✓✓ |
| Pulse repetition frequency (Hz) | 1 | ✓✓✓ |
| Duty cycle (%) | not reportedpulse duration × PRF gives 0.062% | ⚑ |
| Sonication duration (s) | 120, 360swept | ✓✓✓ |
| Free-field pressure (kPa) | 630, 240, 800swept | ✓✓✓⚑ |
|---|---|---|
| Free-field Isppa (W/cm²) | 26.3 | ✓✓✓ |
| Free-field Ispta (W/cm²) | 0.0165 | ✓✓✓ |
| 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 |
In vivo: burst-tone mode ultrasound applied unilaterally to lumbar DRGs (L3-5 for CFA model, L4-6 for CCI model) at peak negative pressure 0.63 MPa, burst length 625 microseconds (250 cycles), PRF 1 Hz, for a 6-min stimulation session, repeated daily for four consecutive days (three consecutive days in the GABA-antagonism/bicuculline experiment, with intra-DRG bicuculline or saline injected 10 min before FUS on day 2). Pain responses were assessed before (daily/chronic response) and 30 min after (acute response) each session. Ex vivo: primary cultured DRG cells received a 2-min FUS sonication at 0.24-0.8 MPa (0 MPa in control) from below a 96-well culture plate.
Flags from extraction
n_subjects— Group sizes differ by sub-experiment and are not summed to a single total: N=5/group in the CFA analgesia/protein experiments and in the bicuculline experiments (Figs. 3, 4, 7, 8); control/control+FUS N=6 and CCI/CCI+FUS N=11 in the CCI experiments (Figs. 5, 6). Given as a list per instructions.n_sessions_per_subject— Most experiments (main CFA and CCI analgesia/mechanism studies) used FUS for four consecutive days, but the GABA-antagonism (bicuculline) experiment used three consecutive days; 4 is given as the modal value with this flag.exposures[0].free_field.pressure_kpa— 630 kPa is the fixed in vivo focal-spot peak negative pressure (explicitly stated to be from the free-field pressure distribution, Fig. 1A); 240 and 800 kPa are the ex vivo DRG-culture sonication range (0.24-0.8 MPa), whose domain (free field vs. through culture medium) is not explicitly labelled but is assumed comparable to the in vivo free-field calibration.exposures[0].timing.duty_cycle_pct— Duty cycle is not explicitly stated; it is derivable from burst length (625 microseconds) and PRF (1 Hz) as 0.0625%, but this would be the extractor's own arithmetic, so left not_reported per instructions.sham_type— Comparator groups (CFA-only, CCI-only, i.e. no FUS) are untreated/no-stimulation controls rather than a sham TUS condition (no inactive transducer or active control site is described); coded as 'none'.