RA:Increases the concentration of monoamines (dopamine, norepinephrine, 3,4-dihydroxyphenylacetic acid, and levodopa) in the cerebral cortex of mice.Downregulates the expression of MAO B in the substantia nigra and ventral tegmental area, regions involved in dopamine synthesis. These changes were linked to a suppression of Aβ aggregation in the brains of the AD model mice, suggesting that RA has a potential therapeutic effect against AD by enhancing the dopamine-signaling pathway and inhibiting Aβ aggregation. The gene discussed is MAOB; the disease is Alzheimer disease.