SHORT NOTE - EXTRAPINEAL MELATONIN AND EXOGENOUS SEROTONIN IN SEASONAL AFFECTIVE-DISORDER

Visible light inhibits the binding of melatonin and serotonin to cultu red human peripheral blood mononuclear leukocytes (PBMLs) in winter. T he decreased binding switches the metabolism in PBMLs towards serotoni n synthesis, resulting in the reduced production of melatonin. The ing estion of L-tryptophan during the day is hypothesized to increase the levels of melatonin, released from the gastrointestinal tract, in pati ents with winter seasonal affective disorder (SAD). Due to the relativ e shortage of light, coincident with a predisposed metabolic error, th ere would be no switch towards serotonin synthesis among winter SAD pa tients in winter. The rate of serotonin synthesis could thus remain in adequately low to maintain optimal mood in winter SAD patients.