There is a method to focus on urinary metabolites dynamics to estimate the brain monoamine nervous system activity of a human. In Homovanillic acid of Dopamine final metabolite and 3-Methoxy-4-hydroxyphenylglycol of Noradrenaline final metabolite, excretion mechanism by transporter expressed on the blood-brain barrier has been revealed, and brain-urine correlation has also been reported. On the other hand, in the 5-HT nervous system, the excretion mechanism of brain-peripheral is shown, but the association of the brain-urine of the 5-HT metabolism are not yet clarified. In the present study, we investigated the correlations between urinary 5-hydroxyindoleacetic acid （5-HIAA） excretion levels and the brain 5-HT content. By using 5,7-dihydroxytryptamine （5,7-DHT） that is a neurotoxin, the brain 5-HT can destroy specifically. Our intention was to clarify brain-urine correlations. The results showed that after a bilateral intraventricular microinjections of 5,7-DHT, hippocampal 5-HT and 5-HIAA content （p<0.001） as well as urinary 5-HIAA excretion were decreased （p<0.001） in comparison to the vehicle-administered group. Furthermore, a strong positive correlation was observed between urinary 5-HIAA and hippocampal 5-HT and 5-HIAA content （p<0.001）. In conclusion, it was revealed that the brain 5-HIAA content reflects a 5-HT content in the brain. Furthermore, urinary 5-HIAA excretion dynamics became the noninvasive biomarker of the 5-HT nervous system activity in the brain.