Spinal cord expression of two-pore-domain K⁺ channel transcripts. Transverse sections from rat cervical spinal cord were hybridized with [³³P]-labeled cRNA probes and subsequently dipped in liquid autoradiographic emulsion. Silver grains were imaged using dark-field and bright-field microscopy. Top panels (A–D) show broad distribution of TASK-1 and TASK-3, with low-to-moderate accumulations of silver grains over many neurons. Ventral horn motoneurons were intensely labeled for both transcripts. In the alternate panels (B,D), these same motoneurons are shown at higher power using bright-field optics, with the corresponding cells indicated byarrows. Bottom panels (E–H) show dark-field images of labeling for the other transcripts in the spinal cord. Labeling for these transcripts was lower, although there were moderate levels of TREK-2 in spinal cord interneuron layers (F). Scale bar: A,C, E–H, 400 μm; B,D, 100 μm.