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: Next we performed a quantitative comparison of the Kv2.1 densities in 18 axo-somato-dendritic compartments of CA1 PCs (Table 2). The densities of immunogold particles for the Kv2.1 subunit in the somato-dendritic compartments and axon terminals were calculated from single-labelling experiments. Somata and proximal apical dendrites contained high densities of gold particles, which were significantly (anova, P < 0.001; Dunnett's post hoc test, P < 0.001; n = 3 rats; Fig. 5A) higher than background. The densities of the Kv2.1 subunit in apical dendrites in the middle and distal SR, SLM tuft dendrites, oblique dendrites, dendritic spines, and axon terminals were not significantly different from the nonspecific background labelling (anova, P < 0.001; Dunnett's post hoc test, P > 0.26; n = 3 rats). The density of the Kv2.1 subunit in AISs was calculated from double-labelling experiments with the Kv1.1 subunit. The strength of the Kv2.1 labelling of somata [11.4 ± 3.8 gold particles per μm2 (gold/μm2)] in these double-labelling experiments was very similar to that found in single-labelling reactions (P = 0.66, unpaired Student's t-test). AISs contained, on average, 11.5 ± 1.8 gold/μm2, which did not differ significantly from the gold particle content of somata (P = 0.97, unpaired Student's t-test), but was significantly above the background (anova, P < 0.01; Dunnett's post hoc test, P < 0.01; n = 3 rats; Fig. 5B).
Affiliation: Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, Budapest, Hungary.