The proanthocyanidins exerted anti-insomnia effect to rats by regulating NO/ADMA/DDAH pathway, showing as increasing levels of 5-HT, GABA and NO, and protein and mRNA expressions of DDAH1, DDAH2 and nNOS, and decreasing levels of NE, Glu, ADMA and 8-isoprostane, in brain (67). Here, DDAH2 is linked to insomnia.