KCNK2 and depressive symptom measurement: TREK-1 knock-out mice displayed a phenotype resistant to depression in five different mouse models of depression: the Porsolt forced swim test (FST), the tail suspension test (TST), the conditioned suppression of motility test (CSMT), the learned helplessness test (LH), and the novelty-suppressed feeding test (NSF) (Table 3; Heurteaux et al., 2006).