Fig. 3.
Paired-pulse ratios for large and small synapses decline at the same rate with repeated testing. SN synapses were tested with paired-pulse stimulation at a 15 sec ITI. Note that, although the average initial paired-pulse ratio at synapses >8 mV (large synapses) was more than twofold smaller than the average initial paired-pulse ratio at synapses <8 mV (small synapses), the paired-pulse ratio at large synapses showed comparable decrement with repeated testing. The average initial EPSP amplitude was 4.7 ± 0.4 mV (n = 21) and 13.1 ± 1.1 mV (n = 12) for the small synapses and large synapses, respectively; these two groups of synapses initially had paired-pulse ratios of 2.60 ± 0.49 and 1.13 ± 0.26, respectively. Data are from the same experiments as in Figure 1C. Note that the paired-pulse ratios for the large and small synapses are plotted on two different scales. The time course of the decrease in paired-pulse ratios did not differ significantly between the two groups (F1,31 = 2.19; p = 0.149; repeated measures ANOVA testing trial × initial size interaction; comparison of the second-order polynomial trend).