Objective When food is available during a restricted and predictable time of the day, mammals exhibit food-anticipatory activity (FAA), a daily increase in locomotor activity preceding the presentation of food.Although many studies attempted to locate the food-entrainable circadian oscillator in the central nervous system, the mechanisms for FAA are a matter of controversy.The present study was designed to clarify the role of dopaminergic and histaminergic systems in FAA.Methods The mice were given access to food for 2 h (CT19-CT21) in ICR mice and for 4 h (CT 17-CT21) in gene-manipulated mice.FAA was monitored by infrared locomotor activity sensors and defined as the locomotor activity occurred 2 h before the availability of food.Dopamine D1 receptor (R), D2R, and histamine H1R-specific antagonists, and D2R-and H1R-knockout (KO) mice were used to clarify the role ofdopamine and histamine receptors in FAA induced by food restriction (FR).In addition, brain monoamine concentrations on the 14th day of FR were determined by HPLC-ECD.Results Pretreatment with D1R antagonist SCH23390 at 1, 3, or 10 μg/kg significantly decreased FAA by 19%, 26% or 19%, respectively, and D2R antagonist raclopride at 22, 67, or 200 μg/kg significantly decreased FAA by 16%, 36% or 41%, respectively, as compared with vehicle control.Moreover, co-administration of SCH23390 and raclopride synergistically inhibited FAA by 57%.Consistently, the levels of dopamine and its metabolites in the striatum and midbrain were significantly increased during FR-induced FAA, even in the mice pretreated with D1R and D2R antagonists.Similarly, D2R KO mice exhibited attenuated FAA.However, pretreatment with pyrilamine at 2.5, 5, or 10 mg/kg did not significantly decrease FAA, although it decreased the locomotor activity during the dark period in ad libitum mice, and H1R KO did not affect FAA.Conclusion These results strongly indicate that dopaminergic system plays an essential role in the food-anticipatory activity in mice.