Acamprosate treatment towards the end of the light-phase of a 24 hr LD cycle [ZT 10] does not affect circadian clock phase. Shown are representative, double-plotted actograms of general circadian locomotor activity prior to and during (black line) a daily regimen of i.p acamprosate treatment (300 mg/kg; A, acamprosate in WT; B, acamprosate in Per2 mutant; C, saline in WT; D, saline in Per2 mutant). Black and white bars represent the 12 hrs of lights-off and lights-on periods, respectively.