1 Department of Physiology, Semmelweis University, Budapest
K2P leak K+ channels are major determinants of the resting membrane potential and regulate cellular excitability. The most recently discovered K2P subunit, TRESK is highly expressed in primary somatosensory neurons (including capsaicin sensitive nociceptive afferents). Investigation of the physiological role of TRESK has been impeded by the lack of adequate modulators. We have recently identified a selective activator (cloxyquin) and inhibitor (A2764) of TRESK.
To determine the role of TRESK in regulating the excitability of primary somatosensory neurons and the release of vasoactive neuropeptides.
Dorsal root ganglion (DRG) neurons were isolated from adult wild type and TRESK knockout mice. Membrane potential and rheobase values were measured by whole-cell patch clamp. Changes in cytoplasmic Ca2+ concentration were determined by ratiometric calcium imaging. Meningeal CGRP release was measured by ELISA. Changes in meningeal blood flow were determined using laser Doppler imaging.
Application of the TRESK inhibitor A2764 depolarized the resting membrane potential and decreased the rheobase of DRG neurons isolated from wild type mice. The inhibitor did not influence the resting membrane potential and rheobase of neurons isolated from TRESK KO animals, implying that the effects of A2764 are mediated by TRESK inhibition. Inhibition of TRESK via A2764 increased, while activation of TRESK via cloxyquin decreased the sensitivity of the neurons to capsaicin (as determined by calcium imaging). In rats, A2764 pretreatment increased, while cloxyquin decreased the capsaicin-evoked CGRP release ex vivo. Similar effects were observed on capsaicin evoked changes in meningeal blood flow in vivo.
A2764 increases the excitability of DRG neurons by inhibiting TRESK. Pharmacological manipulation of TRESK can influence the capsaicin sensitivity of isolated DRG neurons. In rats, modulation of TRESK can modify the effects of capsaicin on CGRP release and meningeal blood flow.
Doctoral School: Doctoral School of Molecular Medicine
Doctoral Program: Cellular and Molecular Physiology
Supervisor: Péter Enyedi