Fig. 6.

Mutant varicosities have fewer failures of transmitter release. A, Single traces of focally recorded synaptic current from mutant (left) and control (right) animals. Arrows point to stimulus artifacts, and asterisks indicate events scored as release of transmitter. The events in these traces are unitary quantal events, as judged by their similarity to spontaneously occurring events recorded at the same time. In this recording configuration, the current records represent only a fraction of the total membrane current because of the relatively low seal resistance between the micropipette and the muscle; thus, the scale bars do not represent total membrane current.B, Summary of the mean number of failures of evoked release for mutants (n = 20 sites) and controls (n = 17 sites). The symbols show results obtained from each individual recording site. One hundred stimuli from each site were scored for failure or release.