Low-intensity transcranial focused ultrasound engages parvalbumin-positive GABAergic interneurons in a humanized mouse model of chronic pain: from electrophysiology to cellular investigation

Background: Low-intensity transcranial focused ultrasound (tFUS) offers high spatial specificity and deep brain penetration, showing great promise as a non-invasive stimulation technology for modulating brain activity and behavior. Recent studies show that specific tFUS parameters targeted to pain-processing brain circuits can significantly alter pain-related behaviors in rodent models and humans. However, a comprehensive understanding of how tFUS influences brain networks and cellular mechanisms is essential to optimize efficacy and facilitate safe translation to clinical pain therapies. Objective: We aimed to evaluate the modulation of inhibitory neural circuits induced by tFUS of 40 Hz pulse repetition frequency (PRF) in a humanized mouse model of chronic pain, integrating local and network-level electrophysiological investigations, molecular analyses, and histological assessment to confirm safety. Methods and Results: We used a 128-element random array transducer for stimulation, along with a non-invasive and flexible 30-channel electroencephalography (EEG) to assess local evoked responses, topographical brain activity, and global brain dynamics including excitation and inhibition (E/I) balance. To further assess tFUS neuromodulation effects at the cellular level, we performed immunohistochemistry (IHC) analysis and found that tFUS significantly increased the activity of inhibitory neurons as indicated by elevated expression of Glutamate Decarboxylase 67 (GAD67) and Parvalbumin (PV). Finally, safety was evaluated in the same brain samples used for mechanistic analysis, with blinded histological assessment revealing no signs of tissue damage. Conclusions: These findings provide new evidence that tFUS non-invasively engages PV GABAergic inhibitory circuits in a chronic pain mouse model, supporting its development as a robust neuromodulation strategy.