Fig. 4: In vivo optical recording of strong press (300 g)-induced neuronal activity in intact DRG neurons.

Optical voltage recordings of primary sensory neurons in response to application of a single mechanical force (300 g) to the hindpaw of naïve (a), CFA (b), or SN-CCI (c) animals. Insets, images of DRG cell bodies (white dotted lines) expressing ASAP4.4-Kv. Yellow lines indicate 1.1 kHz line scan regions where ASAP4.4-Kv optical recording signals were acquired. Each trace is the response of a single DRG neuron; (right) expanded view of the boxed region shown on the right. Purple bars indicate the timing of the stimulus application. Representative line scan images in c are shown under the trace. The red arrow marks one of action potentials and red box indicates action potential bursts. Scale bar: 5 μm. d Mean area under the curve (AUC) of ASAP4.4-Kv z-score signals (each dot represents an individual recorded neuron; number of cells = 6, 4 and 4 for naïve, CFA, and SN-CCI groups, respectively, from three biologically independent mice per group; Kruskal-Wallis test with Dunn’s post-hoc test) and GCaMP3 Ca²⁺ transients (violin plot with median (solid line) and quartiles (dashed lines); number of cells = 119, 141 and 106 for naïve, CFA, and SN-CCI groups, respectively, from three biologically independent mice per group; Kruskal-Wallis test with Dunn’s post-hoc test) in L5 DRG neurons in response to 300 g press, and the number of total activated neurons (each dot represents one animal; number of biologically independent mice = 5, 4 and 5 for naïve, CFA, and SN-CCI groups, respectively; Kruskal-Wallis test with Dunn’s post-hoc test). e In vivo intact DRG Ca²⁺ imaging from naïve, CFA, or SN-CCI using Pirt-GCaMP3 mice. (left) Averaged images before application of strong press (300 g). (right) Averaged images after application of strong press (300 g). White arrowheads indicate spontaneously activated neurons in the absence of an applied stimulus. Yellow arrowheads indicate DRG neurons activated by strong press. Scale bar: 100 μm. f Ca²⁺ transients from DRG neurons in response to a strong press (300 g) applied to the hindpaw of Pirt-GCaMP3 mice (grey) from all naïve, CFA, or SN-CCI animals. Traces of averaged Ca²⁺ transients from each group are shown in black, orange, or green. All data are presented as mean values ± SEM.