Fig. 3.
Localization of BKCa channels in dentate gyrus granule cell somata of rat (A–E) and mouse brain (F–H) revealed by post-embedding immunogold labeling. Antibodies conjugated to 10 nm gold particles were applied on Lowicryl embedded ultra-thin sections. (A) A low-power micrograph shows an aspect of a granule cell soma and the very proximal portion of the raising principal dendrite. (B) Immunoparticles labeling BKCa channels are clustered in areas of the somatic plasma membrane with underlying subsurface cisterns (boxed area in A; immunoparticles are indicated with an arrowhead). (C) Specificity of immunolabeling in rat tissue is tested and confirmed by applying the respective pre-immune serum. (D) Outside areas of the plasma membrane with underlying subsurface cisterns, immunoparticles are scattered in the extrasynaptic plasma membrane with low abundance (arrowheads). (E) The postsynaptic membrane specialization of symmetric, presumably inhibitory synapses, is free of BKCa channel immunolabeling (margins of the postsynaptic membrane specialization are indicated with open arrows). (F) As in the rat, clustering of BKCa channels in areas of the plasma membrane with underlying subsurface cisterns is seen in the granule cell soma of mouse (C57Bl/6; BK+/+). (G) Outside these areas, scattered immunoparticles are localized in the extrasynaptic plasma membrane with low abundance (arrowheads). (H) Specificity of immunolabeling is tested and confirmed in sections of BKCa channel null mice (BK−/−). A, axonal profile; AT, axon terminal; GS, glial sheath; PM, plasma membrane; Pre-IS, pre-immune serum; rER, rough endoplasmic reticulum; SSC, subsurface cistern. Scale bar=1.5 μm in (A); 200 nm in (B, D, G); 250 nm in (C, E, H); 500 nm in (F).