ELECTROPHYSIOLOGY OF SYNAPTIC VESICLE CYCLING

Supplementary Data

• Recent publications were reviewed as the paper went to press.
  
  Two recent publication that bear directly on the subject of this review appeared after completion of the manuscript. First, optical monitoring of exocytosis with FM dyes has revealed both continuous and transient modes of exocytosis in bipolar-cell terminals (135). During a 6 s depolarization, a phasic burst of exocytosis increased the surface area of the terminal by a maximum of 12%, corresponding to the fusion of 13,000 vesicles. This agrees remarkably well with the total cumulative increase in capacitance following a train of pulses lasting several seconds (approximately 300 fF, corresponding to 12,000 vesicles; Reference 121). Interestingly, endocytosis was inhibited during the depolarization and resumed only after Ca concentration had begun to fall back to the baseline, which again agrees with conclusions from capacitance measurements (118). Second, different types of FM dye were used, together with a destaining model, to reveal fast endocytosis (τ = 5 s) in conventional synaptic boutons (136), comparable in speed to the rapid endocytosis described using capacitance measurements in bipolar cell terminals (117).

  135. Rouze NC, Schwartz EA. 1998. Continuous and transient vesicle cycling at a ribbon synapse. J. Neurosci. 18:8614–24

  136. Klingauf J, Kavalali ET, Tsien RW. 1998. Kinetics and regulation of fast endocytosis at hippocampal synapses. Nature 394:581–85