Figure 2
EFhd2 knockout (KO) mice display a sensation-seeking/low-anxiety behavioural phenotype that is frequently associated with an enhanced risk for alcohol addiction. (a) In the open-field (OF) test EFhd2 KO mice (n=9) show higher locomotor activity in a novel environment than wild-type (WT) mice (n=12). (b) The latency to enter the anxiogenic centre of the maze for the first time is reduced and (c) EFhd2 KO mice spend more time in the centre of the maze than WT mice. (d) Centre locomotion of EFhd2 KO mice is enhanced in the OF. (e) Locomotion in the periphery of the maze is not altered in EFhd2 KO mice. Also the elevated plus maze (EPM) test suggests reduced levels of anxiety in EFhd2 KO (n=8) compared to WT (n=12) mice. (f) The number of entries into the open arms is enhanced in EFhd2 KO mice. (g) Also, locomotion in the open arms is enhanced. In-depth analysis of anxiety-related behaviour in the EPM shows that major differences between EFhd2 KO and WT mice are derived from behaviour in most anxiety-loaded parts of the maze, that is, the distal part of the arms, as shown by (h) the time spent on proximal (Prox) and distal (Dist) arms of the maze, (i) the locomotor activity on all arms of the EPM, and by (j) the entries in the arms of the EPM. (k) In the forced swim test, EFhd2 KO mice show less immobility (floating) than WT mice. (l) The novelty-suppressed feeding (NSF) test shows a strong tendency for reduced depression-like behaviour in EFhd2 KO mice (n=8) compared to WT (n=11) mice. The latency to eat food in a novel environment is largely reduced in EFhd2 KO mice. (m) Speed of locomotion to search out for the food in the NSF test is significantly enhanced in EFhd2 KO mice, indicating a reduced suppression of feeding by the novelty of the environment. (n) The lack of EFhd2 has no effect on sucrose preference (*P<0.05; **P<0.01).
