Fig. 5.
s1f and s2f recover more quickly than S5–8 after a 40-AP train. (A) Two protocols were used to study the recovery of SV pools after the 40-AP train. In the first protocol, double AP stimulations with a 5-ms inter-AP interval were given after various delay periods following the end of the 40-AP train. This protocol was used to assess the recovery of s1f and s2f. In the second protocol, a single 8-AP test train was given at variable intervals following the end of the 40-AP train. This protocol was used to assess the recovery of S5–8. (B) Cumulative release following the two test APs used to study the recovery of s1f and s2f. Traces with test intervals of 50 ms and 4 s were averaged from four synapses and superimposed with the control from the beginning of the conditioning train. Note the reduced fast component and the enhanced slow component of release for the 50-ms recovery interval. (C) Recovery kinetics for s1f and of s1s. Closed symbols show values after the last AP of the 40-AP train. (D) s1f and s2f, normalized to that of the conditioning 40-AP train and plotted against test interval. Plots were fitted with single exponential functions having a time constant of 160 ms. (E) S5–8, normalized to that of the conditioning train and plotted against test interval. Plot was fitted with a single exponential function having a time constant of 830 ms. n = 4 synapses for each protocol.