Dorsal root ganglion (DRG) neurons express mRNAs for numerous two-pore domain K+ (K-2P) channels and G-protem coupled receptors (GPCR). Recent studies have shown that TRESK is a major background K+ channel in DRG neurons. Here, we demonstrate the pharmacological properties of TRESK, including GPCR agonist-induced effects on DRG neurons. TRESK mRNA was highly expressed in DRG compared to brain and spinal cord. Similar to cloned TRESK, native TRESK was inhibited by acid and arachidonic acid (AA), but not zinc. Native TRESK was also activated by GPCR agonists such as acetylcholine, glutamate, and histamine. The glutamate-activated TRESK was blocked by lamotrigine in DRG neurons. In COS-7 cells transfected with mouse TRESK, 30 mu M lamotrigine inhibited TRESK by similar to 50%. Since TRESK is target of modulation by acid, AA, GPCR agonists, and lamotrigine, it is likely to play an active role in the regulation of excitability in DRG neurons. (C) 2008 Elsevier Inc. All rights reserved.