X-optogenetic inhibition of VTA GABA neurons for wireless deep-brain stimulation and suppression of scratching behavior in freely moving mice.

X-ray-mediated wireless optogenetic neurostimulation (X-optogenetics) at any brain depth is a powerful technology for neuroscience studies and neurological disorder treatment. However, there is still a lack of effective and safe X-optogenetic neural inhibition technology because of the need for a precise spectral match degree between scintillator and inhibitory opsins and sufficient light intensity emitted from X-ray-induced scintillation. Here, we report an efficient X-optogenetic neural inhibition technology that achieves both wireless deep-brain stimulation and rapid behavioral suppression in freely moving mice. First, we developed two novel inorganic scintillators: terbium-doped gadolinium oxysulfide (Gd2O2S: Tb) and europium-doped yttrium oxide (Y2O3: Eu). The Gd2O2S: Tb and Y2O3: Eu can absorb X-ray energy and emit green and red visible light, respectively. We demonstrated that the visible light emitted from X-ray-mediated scintillation effectively activated two inhibitory opsins (ArchT and eNpHR 3.0), which facilitated successful inhibition of the GABAergic neural activity in the ventral tegmental area (VTA) of mice. Further, this X-optogenetic neural inhibition technology wirelessly and significantly suppressed itch-induced scratching bouts (about 52%) in awake, freely moving mice. Importantly, owing to the superior radioluminescence performances of scintillators, our X-optogenetic neural inhibition technology only required a low dose of X-ray (2.78 Gy), which is substantially lower than that (7 Gy) reported in a previous study. By enabling wirelessly efficient and safe neural inhibition in the deep brain, this X-optogenetic technology holds promise for advancing neuroscience investigations and therapeutic applications in large living subjects.