Skip to main content
. 2008 Jun 11;19(3):511–523. doi: 10.1093/cercor/bhn101

Figure 4.

Figure 4.

F-actin labeling in AC and MF terminals in WT and synapsin DKO mice exposed to depolarizing [KCl]o. (A) Schematic drawing of a hippocampal slice with the electrode arrangements in stratum radiatum of the CA1 region. (B) The graph shows an example of the change in fEPSP slope as a function of time when a WT slice is incubated in high [KCl]o (40 mM). Afferent stimulation and synaptic recordings are as depicted in (A). The slopes of the elicited fEPSPs were normalized to the mean value obtained 1 min prior to the start of high [KCl]o wash-in (time zero), and the effects are presented from around 27 min and onward. Filled arrow indicates the time at which the slice was removed from the recording chamber and fixed. Inset: superimposed synaptic responses at times indicated by open arrows and numbers. (C) Electron micrograph from a MF terminal exposed to high [KCl]o in a hippocampal slice from a WT mouse. A synapse is indicated by its postsynaptic density (arrowheads), spine (s), vesicles (v), and mitochondria (m). Scale bar: 0.1 μm. (D) As in (C), but the electron micrograph is from an AC collateral terminal. Boxes represent the EZs analyzed (150 nm lateral to the active zone and 250 nm perpendicular to the active zone, unless further restricted by the size of the terminal). (E, F) As in (C) and (D), but from synapsin DKO mice. (G) Bar graph (mean + standard error of the mean) representing quantitative analyses of F-actin in EZs (gold particles/μm2). Two pairs of WT and synapsin DKO mice were analyzed independently and repeated once (experiments 1 and 2). Twenty electron micrographs (containing 25–33 synapses) were analyzed for each synapse type in each animal. Actin-labeling densities were compared between genotypes. A prominent reduction in DKO compared with WT was observed in MF EZ only, in both experiments (#P ≤ 0.002, *P ≤ 0.03). The nonparametric Mann–Whitney test gave similar results. (H) As in (G), but quantified in the whole terminal. No differences were observed in either experiment. (I) As in (G), but quantified in the dendrites postsynaptic to terminals in (G) and (H) (different scale due to a generally more dense labeling than in G and H). No differences were observed.