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1 Physiology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, North Chicago, IL, USA; Physiology, Gyeongsang National University, Jinju, Korea, Korea, Republic of
2 Physiology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, North Chicago, IL, USA
* To whom correspondence should be addressed. E-mail: dawon71{at}yahoo.com.
Dorsal root ganglion (DRG) neurons express mRNAs for many two-pore domain K+ (K2P) channels that behave as background K+ channels. To identify functional background K+ channels in DRG neurons, we examined the properties of single channel openings from cell-attached and inside-out patches from the cell bodies of DRG neurons. We found seven types of K+ channels with single channel conductance ranging from 14 pS to 120 pS in 150 mM KCl bath solution. Four of these K+ channels showed biophysical and pharmacological properties similar to TRESK (14-pS), TREK-1 (112-pS), TREK-2 (50-pS) and TRAAK (73-pS) that are members of the K2P channel family. The molecular identity of the three other K+ channels could not be determined, as they showed low channel activity and were observed infrequently. Of the four K2P channels, TRESK-like (14-pS) K+ channel was most active at 24°C. At 37°C, the 50-pS (TREK-2-like) channel was the most active and contributed the most (69%) to the resting K+ current, followed by the TRESK-like 14-pS (16%), TREK-1-like 112-pS (12%) and TRAAK-like 73-pS (3%) channels. In DRG neurons, mRNAs of all four K2P channels, as well as those of TASK-1 and TASK-3 were expressed, as judged by reverse transcriptase-PCR analysis. Our results show that TREKs and TRESK together contribute >95% of the background K+ conductance of DRG neurons at 37°C. As TREKs and TRESK are targets of modulation by receptor agonists, they are likely to play an active role in the regulation of excitability in DRG neurons.
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