FIGURE 7.

Assay reveals phasic injury-associated changes in intrinsic axonal/neurite growth capacity in injury-conditioned and uninjured contralateral sensory neurons. Fluorescence photomicrographs depicting βIII-tubulin-immunopositive staining in naïve, ipsilateral injury-conditioned (left column) and contralateral uninjured (right column) L4–L6 dorsal root ganglion (DRG) neurons assayed for 24 hours on laminin and poly-l-lysine coated coverslips (timepoints as indicated). Scale bar = 50 μm. Graph insert (upper right) summarizing the mean (± SEM) total axon/neurite length per neuron relative to naïve from DRG ipsilateral or contralateral to injury at timepoints as indicated (n = 200–250 neurons analyzed/timepoint from 3 separate time courses). Note: intrinsic axon/neurite outgrowth capacity increases significantly (***p < 0.001) following injury with peak outgrowth observed in the 2-day injury group, which qualitatively exhibits both highly arborized and elongating forms of growth, versus the 4- and 7-day injury-conditioned neurons that qualitatively exhibit predominantly the elongating form of outgrowth. In the uninjured contralateral DRG neurons, significantly increased outgrowth is only observed in the contralateral to 1-week injury group and is qualitatively of the predominantly elongating form normally associated with injury-conditioned neurons.