The TASK Family: Two-Pore Domain Background K+ Channels

Neurotransmitters and anesthetics converge on the same TASK-like motoneuronal K⁺ channel and on heterologously expressed TASK-1 and TASK-3. A. (Left) In hypoglossal motoneurons, serotonin (5-HT) completely inhibits the K⁺ current activated by a supramaximal concentration of halothane (see dashed line). (Right) The averaged current–voltage (I-V) relationship of the joint halothane- and 5-HT-sensitive K⁺ current is fits well with a GHK equation, as expected for the open-rectifier TASK channels (adapted from 68). Experiments were performed with the ZD7288 (a hyperpolarization-activated cyclic-nucleotide-gated channel (HCN)-specific antagonist) in the whole cell recording pipette to block I_h, a current that is also modulated by 5-HT and halothane. B. The pH-sensitive K⁺ currents induced by transient transfection of TASK-1 (left) and TASK-3 (right) into TRH-R1-expressing HEK 293 cells are activated by halothane, and the halothane-activated current is completely blocked by TRH. Inset: TASK currents taken from the indicated points (a, b, c) show a weak voltage-dependence like that of the motoneuronal halothane- and 5-HT-sensitive K⁺ current (adapted from 44).