Fig. 1. Threshold change versus time in 2- (n = 10), 4- (n = 8), and 16- (n = 8) week-old animals for partial sciatic nerve ligation (PSL). The left paw in the treated animals was compared to the left paw in the control animals with no surgery. The vertical solid line above the graph is the median time to return to 80% of control threshold, and the horizontal solid line is the range. The median time to return to 80% of control values was shorter in the 2-week-old animals than in either the 4- or 16-week-old animals ( P < 0.05). * Significantly different from baseline threshold. The 2-week-old animals are the only group that did not have development of a threshold different from baseline.