Figure 2.

Survival and treatment of animal for histological analysis. Survival without doxycycline treatment is indicated by minus symbols (−−−), and treatment with doxycycline in the drinking water is indicated by plus symbols (++++). To examine effects of regulatable NT-3 gene delivery on axonal regeneration, NT-3 and GFP, respectively, are continuously turned on or off for 4 weeks. To determine whether transient NT-3 gene delivery is sufficient to sustain regenerated axons, gene expression was first turned on (no doxycycline) for 4 weeks followed by doxycycline treatment for 6 weeks (−−−followed by++++).