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. Author manuscript; available in PMC: 2011 May 24.
Published in final edited form as: Cereb Cortex. 2006 Apr 28;17(3):702–712. doi: 10.1093/cercor/bhk021

Figure 6.

Figure 6

Subcellular localization of HCN2 channels in developing hippocampus. (A–D) Low-magnification photographs demonstrate distribution of HCN2 channels on P2 (A), P11 (B), P18 (C), and P90 (D). In contrast to HCN1, HCN2 somata can easily be discerned in the P11 CA1 pyramidal cell layer, in both PV+ interneurons and PV–, presumed pyramidal, neurons. Localization of HCN2 channels in dendritic field of CA1 is apparent later in hippocampal maturation, as confirmed by high-resolution dual labeling: (E, F) Dual labeling of HCN2 (red) and MAP-2 (green) reveals overlapping expression in CA1 stratum lacunosum-moleculare (slm) on P90 (F), but not on P11 (E), suggesting that, compared with HCN1 (Fig. 3), dendritic trafficking of HCN2 channels commences at a later stage of CA1 pyramidal cell differentiation. Note that the pattern of HCN2 immunoreactivity is more punctate than that of HCN1, but this does not delineate presynaptic location: HCN2 fails to colocalize to GABAergic (GAD65) or glutamatergic (VGLUT1) afferents to the dendrites in slm. (G, H) Similar to HCN1, HCN2 signal over the pyramidal cell layer in CA3 (arrows in B,C, and D) is attributable to expression of HCN2 channels in axons and terminals as well as somata of basket cells. PV+ (G, arrowheads) but never CCK+ basket cells (H) colocalize HCN2. sr, stratum radiatum; asterisks demarcate the hippocampal fissure. Confocal microscope virtual slice thicknesses: (A–D) = 15 μm, (E, F) (MAP-2-HCN2) = 1 μm. (F) (GAD65 and VGLUT) = 0.5 μm. Scale bar: (A–D) = 900 μm; (E) = 27 μm (left panels), 13.5 μm (right panel); (F) = 27 μm (left and right panels), 13.5 μm (middle panel); (G, H) = 120 μm (left panels), 60 μm (right panel).