(A) Littermates were used in parallel for the preparation of perfusion fixation or acute hippocampal slices that were immersion-fixed after 0 or 60–180 min incubation in oxygenated aCSF, followed by regular immunohistochemistry. Selected vibratome slices were synchronously used for recordings of evoked field excitatory postsynaptic current (fEPSC). (B) Representative traces of field fEPSC in an acute hippocampal slice. Recordings were initiated 1 h after vibratome preparation of the slices. The recordings showed that fEPSC remained stable for the 2 h of recordings. (C,D) Histograms comparing the amplitudes and half-width durations of fEPSC in all experiments (N=5, Mean ± sem, P>0.5, ANOVA).