Forced swim test. A significant effect of genotype was found in the percentage of immobility [F(2,78) = 3.457; P < 0.05]. Independent ANOVAs showed that in wild types, immobility increased throughout the session [F(2,52) = 8.9, P < 0.001], while it did not change in the knockouts [F(2,52) = 2.3, P > 0.1]. As no significant effect of sex was found in any category, the two sexes were pooled. n = 27 mice per genotype. ∗∗, P < 0.01.