dopamine levels in the nucleus accumbens were increased. These findings indicate that degradation of monoamines is regulated by the circadian clock. It is very likely that the described clock-mediated regulation of monoamines is relevant for humans, because single-nucleotide polymorphisms in Per2, Bmal1, and Npas2 are associated in an additive fashion with seasonal affective disorder or winter depression. See also Clock (gene) Bmal1/Arntl (gene) Suprachiasmatic nucleus (SCN) Per (gene) Steven McKnight (scientist) References External links Steven McKnight, the first scientist to implicate Npas2 as a contributor to circadian rhythms Transcription factors PAS-domain-containing proteins