1. Ca2+-dependent recovery does not contribute to steady-state transmission.
Ca2+-dependent recovery does not contribute to steady-state transmission. A, Example traces illustrating Ca2+-dependent recovery at cartwheel synapses. Top, Train of 3 pulse stimuli at 200 Hz (black arrow) did not enhance recovery (red arrowhead) from synaptic depression. Middle, Train of 20 pulse stimuli at 200 Hz (black arrow) did enhance recovery (red arrowhead) from synaptic depression. Bottom, When 1 mm EGTA was included in the presynaptic recording pipette, the 20 pulse stimuli at 200 Hz (black arrow) could no longer enhance the recovery (red arrowhead) from depression. Traces are averaged from at least 15 trials. Top, Middle, From the same cell. Recovery was tested 100 ms after the end of train stimulation. B, Summary of the recovery from depression under the three conditions shown in A. Recovery was measured as the fraction of the peak amplitude of the IPSC1. Recovery from 200 Hz × 3 stimuli: 0.18 ± 0.02, n = 5; recovery from 200 Hz × 20 stimuli: 0.36 ± 0.05, n = 5; recovery from 200 Hz × 20 stimuli in 1 mm EGTA: 0.13 ± 0.01, n = 6. Recovery from 200 Hz × 20 is significantly larger than that from 200 Hz × 3 (*p = 0.01, paired t test) or that in 1 mm EGTA (*p = 0.003, unpaired t test). C, Kinetics of synaptic depression in response to a 10 Hz → 200 Hz stimulation when 1 mm EGTA was included in the presynaptic pipette (red, n = 5) is not significantly different from control (black, n = 15). p > 0.05 (for every stimulus number, unpaired t test).
Hsin-Wei Lu, and Laurence O. Trussell J. Neurosci. 2016;36:
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