Previous studies have shown that plasma dopamine and its metabolites changes with circadian rhythm not only just in humans (Sowers and Vlachakis, 1984), but also in CSF in primate animals (Perlow et al., 1977) and in the striatum of rat (Schade et al., 1995; Castaneda et al., 2004). Another study indicated that the dopamine receptor responsiveness is modulated by the circadian rhythm at the level of spinal cord in decapitated Drosophila melanogaster (Andretic and Hirsh, 2000). Moreover, it has been revealed that sensitivity of dopamine receptors increased at night at the level of tubero-infundibular-dopaminergic system (Garcia-Borreguero et al., 2004). Additionally, a circadian variation of serum iron paralleled the CSF dopamine, as well as the severity of symptoms (Garcia-Borreguero et al., 2004). However, it is unclear whether the brain iron concentrations changes would follow this pattern.