Figure 9.

Minocycline mitigates if not arrests secondary injury and allows damaged axons to recover. The percentage of newly injured and recovered axons was calculated at each time point by dividing the number of new varicosities (N_t) and recovered varicosities (R_t) by the number of varicosities (V_t) at each time point, (F_N(t) = N_t/V_t*100, F_R(t) = R_t/V_t*100). At the 1-hr time point, all varicosities were new; thus, the values are 100% for all groups (solid lines, circles). Likewise, no axons were classified as recovered at 1 hr; these values are 0% for all groups (dotted lines, squares). (A) The TBI-vehicle group had a percentage of new axons with varicosities that exceeded 20% at each time point, with little recovery. At Day 30, the TBI-vehicle group continued to show features of evolving secondary damage, as evidenced by 16.7% percent of new varicosity development. In the TBI-45-min minocycline (B) and TBI-72-hr minocycline (C) groups, a higher percentage of axons had recovered by Day 7 and Day 14, respectively. This recovery surpassed the percentage of new axons with varicosities and occurred a week after the end of the treatment period for each (arrowhead), suggesting long-lasting effects on both secondary injury and recovery. At Day 30, both minocycline treatment groups had no new varicosities. Two-way ANOVA (Percentage of new varicosities, Time: p = 0.001, Treatment p = 0.09; Percentage of recovered varicosities, Treatment: p = 0.73, Time: p = 0.01). Data presented as mean ± SD.