Distinct axo-somato-dendritic distributions of three potassium channels in CA1 hippocampal pyramidal cells.
Bottom Line: The Kv2.1 subunit was found in somatic, proximal dendritic and AIS plasma membranes at approximately the same densities.A quasi-linear increase in the Kir3.2 subunit density along the dendrites of PCs was detected, showing no significant difference between apical dendritic shafts, oblique dendrites or dendritic spines at the same distance from the soma.Our results demonstrate that each subunit has a unique cell-surface distribution pattern, and predict their differential involvement in synaptic integration and output generation at distinct subcellular compartments.
Affiliation: Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, Budapest, Hungary.Show MeSH
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Mentions: For immunofluorescent localisation of the Kv2.1 subunit in the CA1 area, two antibodies recognising non-overlapping epitopes of the protein were used to ensure that our immunosignal was the consequence of a specific antigen–antibody interaction. When the immunoreactions for the Kv2.1 subunit were analysed at low magnification, strong immunolabelling of the SP and proximal part of the SR was observed (Fig. 3A–D), in line with the results of previous work (Trimmer, 1991; Maletic-Savatic et al., 1995; Du et al., 1998; Lim et al., 2000; Misonou et al., 2004; Rhodes & Trimmer, 2006). Interneurons in all CA1 layers also showed somato-dendritic labelling (Fig. 3A and D). High-magnification confocal microscopic images revealed plasma membrane-like labelling of somata, proximal apical and basal dendrites (Fig. 3E). Double-labelling experiments for Kv2.1 and Nav1.6 (Fig. 3E–K) revealed a clustered Kv2.1 labelling of AISs, confirming the results of Sarmiere et al. (2008). Interestingly, high-magnification single confocal images indicated that these Kv2.1-positive clusters did not overlap with the Nav1.6 containing parts of AISs (Fig. 3K).
Affiliation: Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, Budapest, Hungary.