Diurnal gene expression profiles in mouse brain tissues constituting the central dopamine system

The circadian regulation of gene expression underlies orchestrated daily rhythms in physiology, metabolism, and behavior. The central dopamine (DA) system arising from DA neurons in the ventral midbrain has been implicated in a wide range of brain functions. Growing evidence suggests that DA transmission follows daily oscillations at multiple regulatory steps, and its dysfunction is closely related to the onset of various neuropsychiatric diseases. We examined diurnal gene expression profiles across key brain areas constituting the central DA pathways in mice by use of microarray analyses to identify rhythmically expressed genes according to the time of day (TOD). Male C57BL/6 mice were entrained to a 12-h light-dark (LD) photoperiod, and sacrificed from the Zeitgeber time 11 (ZT11) at 4-h intervals for 2 successive days. Four brain tissues including the substantia nigra and ventral tegmental area of the ventral midbrain (SN/VTA), prefrontal cortex (PFC), striatum (STR), and habenula (HAB), were bilaterally dissected from 1-mm-thick brain slices, which were coronally sectioned in a brain matrix chilled on ice. A total of 48 RNA samples were analyzed by use of Affymetrix GeneChip Mouse Gene 2.0 ST Array (Affymetirx, Santa Clara, CA, USA).