Neuronal activity of RtcB inhibits axon regeneration. (A) Percentage of axons that regenerated back to the DNC after 24 h. Number of axons cut per genotype from left to right: 62, 99, 18, 46, 51, and 24. (B) Representative micrographs of GABA motor neurons 24 h after axotomy in control animals and RtcB mutants. VNC indicates ventral nerve cord. DNC indicates dorsal nerve cord. (Scale bar: 10 μm.) (C) DNC regeneration of control and RtcB mutant animals 6 h after axotomy. Number of axons cut per genotype from left to right: 113 and 35. (D) DNC regeneration of control and RtcB mutant animals 48 h after axotomy. Number of axons cut per genotype from left to right: 105 and 47. Error bars indicate 95% confidence interval. N.S., not significant; **P < 0.005; ***P < 0.0005.