Figure 5.

Short-term plasticity is enhanced in HIP1^−/− mice. A, Sample fEPSP traces evoked by delivering paired pulses 40 or 60 ms apart (only the second response is shown for the latter) to CA3–CA1 synapses from wild-type (blue lines; top traces) and HIP1^−/− mice (red lines; middle traces). Traces represent average from three hippocampal slices per genotype selected for similar average initial fEPSP slope. Traces have been superimposed in the bottom panel for comparison. ACSF contained 2.0:2.0 mm ratio of Ca²⁺/Mg²⁺. B, PPF is significantly increased in HIP1^−/− neurons (n = 18) compared with wild-type littermate controls (n = 17). Interpulse intervals between paired pulses were varied between 40 and 600 ms. Each measurement represents the mean ± SEM (t test, *p < 0.04). PPF is elevated but no longer significantly different in HIP1^−/− neurons (n = 20) under increased release probability conditions (Ca²⁺/Mg²⁺ ratio was increased to 2.5:1.3) in comparison with wild-type neurons (n = 17; mean ± SEM).