Tandem-pore K+ channels display an uneven distribution in amphibian retina

Previous studies in retinal glial (Muller) cells have suggested that the dominant membrane currents are mediated by K+ inward-rectifier (Kir) channels. After blockade of inwardly (Kir) and outwardly (K-D and BK) conducting channels, a large K+ conductance remains, but its nature has not been determined. Tandem-pore K+ channels are likely candidates for this potassium conductance and the purpose of the present study was to determine, using immunocytochemistry, whether Muller cells express TASK-1, TASK-2, TREK-1 and/or TREK-2 potassium channel subunits. The results reveal that retinal glial cells express TASK-1 and TASK-2 subunits, but not TREK-1 or TREK-2 subunits. Furthermore, the distribution of TASK subunits differs from that of Kir channels and may contribute to the potassium conductance of Muller cells.