Figure 3.

A–H, Time course changes in wakefulness of D₂R KO mice after intraperitoneal administration of modafinil at four doses (A–D) or after pretreatment with D₁R antagonist SCH23390 before modafinil (E–H). Each circle represents the hourly mean amount of wakefulness. Open and closed circles stand for the baseline- and experimental-day profiles, respectively. On the experimental day, modafinil was given at 10:00 A.M., as indicated by the closed arrow, and pretreatment with the D₁R antagonist was done at 9:30 A.M., as indicated by the open arrow. The vehicle was used on the baseline day. The horizontal open and filled bars on the x-axes indicate the 12 h light and dark periods, respectively. Values are the means ± SEM (n = 6–8; 6 mice used in E and B; 7 in A, D, F, and H; and 8 in C and G). *p < 0.05, **p < 0.01 by the paired t test.