Mean (+1SEM) forebrain mRNA levels of per1, per2, dbp, and ldha (top to bottom panels) for AK (left), B6 (middle) and D2 (right panels) mice after sleep deprivations (SD) of 1-, 3-, and 6 h (red bars). All SDs started at light-onset (ZT0). Control animals (grey) were sacrificed along with the SD animals. Effects of recovery sleep on expression were assessed by allowing 2 h of recovery (REC) after 6 h SD (ZT8). per1, per2, and dbp, but not ldha expression, was affected by SD, genotype, and time-of-day (3-way ANOVA factors 'SD' and 'genotype': P < 0.0001, factor 'ZT': per1 P = 0.0002, per2 P = 0.004, dbp P < 0.0001). For both per genes the SD effect differed among genotypes ('SD'-'genotype' interaction: per1: P = 0.039; per2: P = 0.006). Linear regression lines (red) describe the time course of mRNA changes during SD (ZT1 through ZT6; see Fig.2). Asterisks and crosses mark times when SD differed from controls (P < 0.05 and P < 0.10, respectively; post-hoc t-tests). Symbols 'a' (> AK) and 'b' (> B6) mark strain differences for each time point and condition (P < 0.05; post-hoc Tukey).