RT Journal Article SR Electronic T1 Amide Local Anesthetics Potently Inhibit the Human Tandem Pore Domain Background K+ Channel TASK-2 (KCNK5) JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 84 OP 92 DO 10.1124/jpet.103.049809 VO 306 IS 1 A1 Christoph H. Kindler A1 Matthias Paul A1 Hilary Zou A1 Canhui Liu A1 Bruce D. Winegar A1 Andrew T. Gray A1 C. Spencer Yost YR 2003 UL http://jpet.aspetjournals.org/content/306/1/84.abstract AB Blockade of voltage-gated sodium (Na+) channels by local anesthetics represents the main mechanism for inhibition of impulse propagation. Local anesthetic-induced potassium (K+) channel inhibition is also known to influence transmission of sensory impulses and to potentiate inhibition. K+ channels involved in this mechanism may belong to the emerging family of background tandem pore domain K+ channels (2P K+ channels). To determine more precisely the effects of local anesthetics on members of this ion channel family, we heterologously expressed the 2P K+ channels TASK-2 (KCNK5), TASK-1 (KCNK3), and chimeric TASK-1/TASK-2 channels in oocytes of Xenopus laevis. TASK-2 cDNA-transfected HEK 293 cells were used for single-channel recordings. Local anesthetic inhibition of TASK-2 was dose-dependent, agent-specific, and stereoselective. The IC50 values for R-(+)-bupivacaine and S-(–)-bupivacaine were 17 and 43 μM and for R-(+)-ropivacaine and S-(–)-ropivacaine, 85 and 236 μM. Lidocaine (1 mM) inhibited TASK-2 currents by 55 ± 4%, whereas its quaternary positively charged analog N-ethyl lidocaine (QX314) had no effect. Bupivacaine (100 μM) decreased channel open probability from 20.8 ± 1.6% to 5.6 ± 2.2%. Local anesthetics [300 μM R-(+)-bupivacaine] caused significantly greater depolarization of the resting membrane potential of TASK-2-expressing oocytes compared with water-injected control oocytes (15.8 ± 2.5 mV versus 0.1 ± 0.05 mV; p < 0.001). Chimeric TASK-1/TASK-2 2P K+ channel subunits that retained pH sensitivity demonstrated that the carboxy domain of TASK-2 mediates the greater local anesthetic sensitivity of TASK-2. These results show that clinically achievable concentrations of local anesthetics inhibit background K+ channel function and may thereby enhance conduction blockade. The American Society for Pharmacology and Experimental Therapeutics