Figure 4.

Ultrastructural localization of KCC2 in LSO neurons during maturation. Location of KCC2 molecules in the LSO of P4 (A, C, E, F) and P12 (B, D, G, H) rats, revealed with the preembedding immunogold technique. A, B, Semithin sections with labeled neurons in the LSO. Silver-intensified gold particles were found at the presumed surface of somatic and dendritic membranes (arrows). C, D, High-magnification electron micrographs illustrated labeled dendritic profiles with boutons (asterisks) making asymmetrical synapses (arrowheads) onto the dendrite. KCC2 was localized homogenously along the perisynaptic and extrasynaptic membranes at both ages. The postsynaptic thickening was almost devoid of KCC2 (arrowheads). E–H, High-magnification ultrastructural analysis showed even distribution of gold particles at perisynaptic sites (arrows) of excitatory (E, G) and inhibitory (F, H) synapses (asterisks). n, Neuronal soma; d, dendrite. Scale bars: (in A) A, B, 30 μm; (in C) C–H, 500 μm.