Figure 2.

Behavioral phenotype of Atm-deficient mice. (A) The Atm−/− mouse is hyper-reactive to d-amphetamine. (Upper) Illustration of the locomotion of a KO mouse placed in the open field for 3 min under control conditions (Left) and after an injection of d-amphetamine (Right). (Lower) Group data for the locomotor activity of the mice before and after injection of d-amphetamine. The numbers of crossings of lines in the open field were counted for each mouse. Atm-deficient mice reacted to the drug much more than control mice. (B) Locomotor activity is impaired in Atm-deficient mice. (Upper) Illustration of footprints of control (wild type, WT) and Atm-deficient (KO) mice. (Lower) Asymmetry of stride length, measured as the difference between adjacent right and left strides, averaged across four Atm and five control mice. After an i.p. injection of l-dopa, the stride length of the same four Atm mice was as before (58.2-mm mean stride length before, 60.4-mm mean stride length after the drug) but it became more symmetric and not different from that of control mice. The mean stride length of control mice was 68.0 mm, and the asymmetry was small and not significant.