“…For instance, rhythmic expression of Per1 and Per2 mRNA is observed in forebrain structures such as olfactory bulbs, piriform and cerebral cortices, hippocampus, paraventricular and arcuate hypothalamic nuclei (Asai et al, 2001;Wakamatsu et al, 2001;Abe et al, 2002;Granados-Fuentes et al, 2004). PER2 expression has also been reported in limbic structures, such as amygdala and bed nucleus of the stria terminalis (Amir et al, 2004;Lamont et al, 2005). Except for the SCN in which the rhythm of PERs follows the mRNA expression by 4-6 h (Field et al, 2000;Mendoza et al, 2007), little is known about the exact timing of both PER1 and PER2 oscillations in forebrain structures.…”