Electric Field Stimulation for the Functional Assessment of Isolated Dorsal Root Ganglion Neuron Excitability

Genetically encoded calcium indicators have proven useful for characterizing dorsal root ganglion neuron excitability in vivo . Challenges persist in achieving high spatial–temporal resolutions in vivo , however, due to deep tissue imaging and motion artifacts that may be limiting technical factors in obtaining measurements. Here we report an ex vivo imaging method, using a peripheral neuron-specific Advillin-GCaMP mouse line and electric field stimulation of dorsal root ganglion tissues, to assess the sensitivity of neurons en bloc . The described method rapidly characterizes Ca 2+ activity in hundreds of dorsal root ganglion neurons (221 ± 64 per dorsal root ganglion) with minimal perturbation to the in situ soma environment. We further validate the method for use as a drug screening platform with the voltage-gated sodium channel inhibitor, tetrodotoxin. Drug treatment led to decreased evoked Ca 2+ activity; half-maximal response voltage (EV 50 ) increased from 13.4 V in untreated tissues to 21.2, 23.3, 51.5 ( p < 0.05), and 60.6 V ( p < 0.05) at 0.01, 0.1, 1, and 10 µ M doses, respectively. This technique may help improve an understanding of neural signaling while retaining tissue structural organization and serves as a tool for the rapid ex vivo recording and assessment of neural activity.