Hyperactivity in the staircase test linked to gene dosage and autoantibody levels in experimental antiphospholipid syndrome factor V Leiden (eAPS-FVL) mice. Behavioral measurements in the staircase test included activity and exploration. The results are presented as mean number of events (percentage of the control group (FVL-control)). (A) For the activity parameter (stair-climbing), FVLQ/+-APS and FVLQ/Q-APS mice were hyperactive compared with both their FVLQ/+-control (FVL-control) group and the FVL+/+-APS mice. (B) For the exploratory parameter (rearing), the FVLQ/Q-APS mice had significantly higher levels of exploration compared with the FVLQ/+-controls (FVL-control), whereas no significant difference was found between the FVLQ/+-APS mice and the controls (P = 0.006 and P = 0.29, respectively). Cumulative data from two independent experiments (FVLQ/+-control, n = 15; FVLQ/+-APS, n = 8; FVLQ/Q-APS, n = 7; FVL+/+-APS, n = 10).