Figure 2.

Pharmacogenetic reduction of neuronal excitability stimulates axon regeneration

(A) Representative whole-cell recordings from an hM4Di-mCherry⁺ adult mouse DRG neuron injected with current before (baseline) and after administration of 10 μM clozapine dihydrochloride.

(B and C) Change in membrane resistance (B) and membrane potential (C) of DRG neurons. Values are plotted as mean ± SEM; ^∗p < 0.05 in (B) and (C), tdTomato⁺ versus hM4Di-mCherry⁺ by Student’s t test (n = 12 tdTomato⁺ and 14 hM4Di⁺ neurons).

(D) Timeline of (E) and (F).

(E) Multiphoton tile scan of GFP⁺ sensory axons (yellow) and GFAP⁺ astrocytes (blue) in the unsectioned spinal cord after complete dorsal column SCI in the given conditions. Asterisks indicate lesion centers. Scale bar, 200 μm.

(F) Quantification of (E). Scatterplot with means; ^∗∗∗p < 0.001, ^∗∗p < 0.01, ^∗p < 0.05, and ^#p < 0.1 by permutation test. n = 8, 8, 7, and 7 for control sham, hM4Di sham, control PNL, and hM4Di PNL, respectively.

(G) In vivo tile scan images of GFP⁺ sensory axons 0 and 3 days after SCI. Asterisks indicate the lesion epicenters; cyan arrowheads point to distal tips of regenerating axons. Scale bar, 100 μm.

(H) Quantification of (G) and comparison with the conditioning paradigm. Scatterplot with means; ^∗∗∗p < 0.001, ^∗∗p < 0.01, ^∗p < 0.05, and ^#p < 0.1 by permutation test. n = 6, 7, and 7 for control, hM4Di, and PNL, respectively.

See also Figure S4 and Video S1.