Postembedding immunogold labeling reveals a change in α4 but not in δ subunit location from perisynaptic to synaptic sites in the molecular layer of the dentate gyrus after CIE treatment. A, C, In saline-treated rats, colloidal gold labeling of the α4 subunit (arrows) was present on or near the plasma membrane of dendrites (D) that contacted axon terminals (T). Gold particles were found predominantly at the outer edges of symmetric synapses (arrows) but not at the center of these synapses (arrowheads). B, D, After CIE treatment, labeling for α4 subunits was found mainly in the center of symmetric synapses (arrows). E, Quantitative analysis showed that perisynaptic labeling was found at 93% of α4 subunit-labeled synapses (open bar) in saline-treated rats (n = 3 rats). In CIE-treated rats (n = 3), perisynaptic labeling was observed at 22% (open bar) of labeled synapses, but synaptic labeling was evident at 78% of labeled synapses (black bar). *p < 0.001 between saline and CIE groups. Error bars represent SEM. F, In contrast to the α4 subunit labeling (B, D), δ subunit labeling (arrow) in CIE-treated rats was present at perisynaptic locations but not within the synaptic contact (arrowhead). Scale bars, 0.1 μm.