GCaMP fiber photometry reveals mechanistic insights into focused ultrasound neuromodulation in acute seizures

Abstract

Generalized seizures represent a major clinical challenge in epilepsy, often resistant to pharmacological treatment and associated with significant morbidity. While low-intensity focused ultrasound (FUS) has emerged as a promising noninvasive neuromodulation strategy to suppress epileptiform activity, the underlying calcium mechanism remains poorly understood. This study, utilizing simultaneous hippocampal GCaMP fiber photometry and electrocorticography (ECoG) in acute pentylenetetrazol-induced seizure mouse models, investigated whether FUS stimulation could modulate intracellular calcium dynamics and network excitability. FUS was applied to the hippocampus with a mechanical index of 0.2, a duty cycle of 7.5%, and a total duration of 10 min. Our findings demonstrated a strong correlation between epileptic calcium transients and ECoG spikes, and FUS significantly attenuated both modalities for up to 40 min. Immunofluorescence analyses in the dentate gyrus revealed decreased c-Fos expression co-localized with both NMDAR2B and GAD65/67 after FUS treatment, indicating an overall reduction in both excitatory and inhibitory synaptic transmission. These results suggest that low-intensity FUS exerts calcium-dependent anti-seizure effects by modulating the excitatory-inhibitory balance. By providing real-time insights into neural network excitability, GCaMP fiber photometry complements traditional electrophysiology and serves as a potent mechanistic surrogate for assessing therapeutic efficacy, potentially guiding future closed-loop neuromodulation strategies.