Figure 7. A small reduction in quantal size is observed after intense release of synaptic vesicles triggered by α-latrotoxin.

A, representative experiment from confluent culture. mEPSCs were recorded in the absence of calcium (no calcium was added to the external solution). α-Latrotoxin (α-Ltx) at 0.5 nM caused a large increase in the mEPSC frequency which gradually declined until it was actually below the original resting level. In the latter condition, a small reduction in quantal size is observed. Access resistance (R_s) of the recording pipette did not change significantly during the recording. A 10 min region was blanked out to compress the display of the experiment. B, amplitude (Amp) and frequency (Freq) of mEPSCs collected after intense release of synaptic vesicles by α-latrotoxin. When compared to the values under resting condition, a reduction in both amplitude and frequency of mEPSCs is seen (amplitude = 79 ± 7 % of control value; frequency = 29 ± 12 % of control value; n = 5).