Fig. 3.

Bridge formation increases during reinnervation as synapses strengthen. A, Comparison of the percentage of endplates linked by a bridge 7–8 d after nerve crush, 12 d after nerve crush, and 12 d after nerve resection. More bridges are found 12 d after nerve crush than at 7–8 d (Student'st test; p < 0.001). In addition, more bridges are found in muscles undergoing reinnervation than in muscles that remain denervated by nerve resection (p < 0.001). B,Representative tension curves produced by two muscles in response to 100 Hz tetanic nerve stimulation 8 and 12 d after nerve crush. Theinsert summarizes results from the reinnervation experiments by showing the fraction of the nerve-evoked tension compared to the direct tension at 1300 msec into a 100 Hz train of stimuli. This fraction is much smaller 7–8 d than 12 d after nerve crush, consistent with less effective synaptic transmission at the earlier time points. Values are expressed as mean ± SEM.