Fig. 6.

Ultrastructural analysis of pre- and postsynaptic specializations in excitatory α₂δ subunit triple-knockout/knockdown synapses. (A) Exemplary EM micrographs of synaptic structures show similar presynaptic and postsynaptic differentiation in wild-type control (Left) and α₂δ-2/-3 double-knockout (α₂δ-2/-3 KO) cultured hippocampal neurons (for statistics see text). (B) Exemplary EM micrographs from silver-amplified eGFP-immunogold-stained presynaptic boutons and the corresponding postsynaptic region from double (α₂δ-2/-3) and TKO/KD (triple KO) synapses. (C) Quantitative analyses showing that both the length of the AZ (Left) and the PSD (Middle) were significantly reduced in TKO/KD compared with eGFP-transfected α₂δ-2/-3 double-knockout synapses in separate culture preparations (control eGFP) and nontransfected neighboring synapses within the same coverglass (control nt). In addition to the AZ and PSD length also the thickness, particularly the extension of the PSD from the membrane into the cytosol, was strongly reduced in TKO/KD compared with the respective control synapses [ANOVA with Tukey post hoc test, **P < 0.01, ***P < 0.001; AZ length: F_(2,147) = 11.3, P < 0.001; PSD length: F_(2,147) = 7.5, P < 0.001; PSD extension: F_(2,147) = 44.6, P < 0.001. Horizontal lines represent means and error bars SEM]. Abbreviations in EM micrographs: b, presynaptic bouton; s, dendritic spine; ps, postsynaptic compartment. (Scale bars, 200 nm.)