Objective: Whether peripheral blood 5-hydroxytrptamine (5-HT) levels serve as biomarker for depression diagnosis/response evaluation has not been well determined. This work was explored to address this inconclusive issue.
Methods: Animals were randomized into control group (NC, n=10) and chronic stress model group (CUMS-model, n=20), respectively. Animals in CUMS-model group were subjected to chronic stress, then the modeled animals were randomly subdivided into CUMS subgroup and CUMS + fluoxetine subgroup (CUMS+FLX). After FLX treatment, blood and tissues were collected. 5-HT and relevant protein expression were measured.
Results: In mice model, there was a significant increase in serum 5-HT levels and a significant reduction in plasma 5-HT levels in CUMS-model group compared with NC group, while platelet 5-HT levels had not much change. After FLX treatment, serum and platelet 5-HT levels were significantly decreased in CUMS+FLX subgroup, while plasma 5-HT levels had not much change compared with CUMS subgroup. Chronic stress enhanced colon and platelet SERT expression and FLX treatment mitigated SERT expression. In rats’ model, there was a significant increase in serum 5-HT levels while plasma and platelet 5-HT levels showed little change in CUMS group compared with NC group. After FLX treatment, serum, plasma and platelet 5-HT levels were significantly decreased in CUMS + FLX subgroup compared with CUMS subgroup. The profile of relevant proteins expression changed by FLX were like those in mice.
Conclusion: Serum 5-HT levels might serve as a potential biomarker for depression diagnosis, meanwhile serum and platelet 5-HT levels might respond to antidepressant treatment.