Measurement of Serotonin Distribution and 5 - Hydroxyindoleacetic Acid Excretion after Oral A dministration of Serotonin using HPLC Fluorescence Detection

Serotonin (5 - h ydroxytryptamine) is a well - known neurotransmitter with both central and peripheral functions and is involved in diverse physiological processes. The aim of this study was to determine bioavailability and overall excretion of orally administered serotonin, as well as its metabolism to 5 - hydroxyindole - 3 - acetic acid. Serotonin was administered to mice by oral gavage ( 0, 1 , 10, and 100 mg/kg body weigh t ) . Serum as well as liver and lung tissue sample s were collected at 0.5, 1, 3, 6, 12, and 24 h after administration. U rine and fecal sample s were collected for the entire 24 h post - administration period to determine overall excretion. Serotonin and 5 - hydr oxyindole - 3 - acetic acid levels were measured by a high - performance liquid chromatography - fluorescence detection method. The serum concentration of serotonin increased a dose - and time - dependent manner. Accumulation of serotonin was observed in the various tissues analyzed, primarily in the high dose group. Urinary 5 - hydroxyindole - 3 - acetic acid excretion was higher in treated mice than in untreated mice; however, urinary serotonin levels were unchanged among the treatment groups. In contrast, high levels of serotonin were observed in the feces. The results of the present study provide important information for the use of orally administered serotonin to reduce risk factors associated with life style - related diseases, notably metabolic syndrome.