Fig. 5.

Tyrosine hydroxylase (TH), monoamine oxidase (MAO), and dopamine receptor D3 (DRD3) expression levels. Our model predicts circadian rhythms of TH, MAO, and DRD3 as a result of modulation by clock components REV-ERB (REV), ROR (ROR), and BMAL1-CLOCK (BC) (see Fig. 1). Our model predictions for the expressions levels of TH, MAO, and DRD3 are plotted with gray curves, and the experimental data from [12, 13, 15] are regraphed with red squares. The error bars represent standard deviation. a TH is the rate-limiting enzyme in dopamine (DA) synthesis. Consistent with experimental data from [13], TH levels peak at night and drop to around 0.5 of the peak value during the day. RMSE=0.05.b MAO is essential for the degradation of DA. Consistent with experimental data from [15], MAO levels are nearly antiphasic to TH, and drop to around 0.79 of the peak value. Additionally, the roles of TH and MAO in the DA system, along with their patterns of expression, are consistent with the fact that mice are nocturnal and therefore need more DA at night. It has been confirmed experimentally by Castañeda et al. [16] that DA levels in the rat brain peak during night. RMSE=0.04.c The dopamine receptor D3 (DRD3) is a DA receptor subtype thought to play an important role in cognition [32]. We model circadian rhythms of DRD3 as a result of repression by REV-ERB and activation by ROR in the mouse ventral striatum, and compare with experimental data from [12]. RMSE=0.12