Laminar distribution of two-pore-domain K⁺ channel transcripts in the neocortex. Shown are dark-field micrographs of the somatosensory cortex. The relevant cell body layers (i.e., layer II through layer VI) are indicated on theright, as is the underlying fiber tract [external capsule (ec)]. TASK-3, TRAAK, and TWIK-1 could be seen at appreciable levels in all layers, whereas TREK-1 was highly enriched in layer IV. TASK-1 was expressed at higher levels in a scattering of cells, mostly in layers IV and VI. One of these layer VI cells is marked by an arrowhead and is shown using high-power bright-field optics in the inset on theleft. Scale bar: 250 μm; inset, 50 μm.