KCNK2 and depressive symptom measurement: TWIK-1-related K+ channel 1 (TREK1), a particularly well-studied K2P channel, has been found to be involved in many physiological processes such as neuroprotection against ischemia (Heurteaux et al., 2004), pain perception (Noel et al., 2011), and depression (Heurteaux et al., 2006).