Figure 8. Reduced paired-pulse facilitation at QKO synapses is caused by occlusion.

(A) Schaffer collateral synapses of the hippocampus. Traces are the average of the first two responses during 20 Hz stimulation across the entire data set (inter-pulse interval was 50 ms; n = 8 preparations for WT in 2.6 mM Ca²⁺/1.3 mM Mg²⁺; n = 12 for QKO in 2.6 mM Ca²⁺/1.3 mM Mg²⁺; and n = 5 for QKO in 1.8 mM Ca²⁺/2.1 mM Mg²⁺; * signifies p < 0.05, *** is p < 0.001; Wilcoxon rank sum; bars are mean ± s.e.m.). 1.8 mM Ca²⁺/2.1 mM Mg²⁺ was chosen for these exeriments because the paired-pulse ratio at QKO synapses then matched WT synapses when bathed in 2.6 mM Ca²⁺/1.3 mM Mg²⁺. QKO synapses exhibited even more paired-pulse facilitation when Ca²⁺ was lowered and/or Mg²⁺ increased further. (B). Calyx of Held synapses also exhibited significantly less paired-pulse facilitation in the experiments documented in Figure 3 (** signifies p < 0.01; Wilcoxon rank sum; bars are mean ± s.e.m.). .