Imaging sensory transmission and neuronal plasticity in primary sensory neurons with a positively tuned voltage indicator.

Primary sensory neurons convert external stimuli into electrical signals, yet how heterogeneous neurons encode distinct sensations remains unclear. In vivo dorsal root ganglia (DRG) imaging with genetically-encoded Ca indicators (GECIs) enables mapping of neuronal activity from over 1800 neurons per DRG in live mice, offering high spatial and populational resolution. However, GECIs' slow Ca response kinetics limit the temporal accuracy of neuronal electrical dynamics. Genetically-encoded voltage indicators (GEVIs) provide real-time voltage tracking but often lack the brightness and dynamic range required for in vivo use. Here, we used soma-targeted ASAP4.4-Kv, a bright and fast positively tuned GEVI, to dissect temporal dynamics of DRG neuron responses to mechanical, thermal, or chemical stimulation in live male and female mice. ASAP4.4-Kv revealed previously unrecognized cell-to-cell electrical synchronization and robust dynamic transformations in sensory coding following tissue injury. Combining GEVI and GECI imaging empowers spatiotemporal analysis of sensory signal processing and integration mechanisms in vivo.