Evaluation of peripheral serotonin content and α₂-adrenergic receptor function as potential markers for life-long recurrent depressive disorder by using methodological improvements

Abstract

Objective: We aimed to evaluate the role and the relations between peripheral platelet serotonin content, blood plasma serotonin concentration and the function of platelet α₂-adrenergic receptors (α₂-AR) as potential state or trait biomarkers for recurrent depressive disorder (RDD).

Methods: 26 drug-free patients with life-long RDD and 31 healthy controls were included in the study. Several methodological improvements in blood collection and platelet isolation were implemented following the present standards in Haematology and Light transmission aggregometry.

Results: Our results have shown lower platelet serotonin content, higher plasma serotonin concentration and desensitization of platelet α₂-AR in patients with RDD. The variables were found heterogeneous and mainly influenced by the clinical characteristics of the current episode. High amplitude of the α₂-AR correlated with severe anxious symptoms and high platelet serotonin content (as well as low plasma serotonin levels) were associated with psychotic symptoms.

Conclusions: The evaluated peripheral markers reflect only state (but not trait) abnormalities in patients with current severe episode of RDD. The observed peripheral α₂-AR and serotonin abnormalities are mutually not related and they are probably triggered by different mechanisms.

Keywords:

• Serotonin
• platelets
• α2-AR
• state markers
• recurrent depression
• life-long depression

Acknowledgements

We would like to thank Darko Sazdov, a professional phlebotomist who performed the venipuncture of all subjects, as well as the technicians Dora Koceva, Jasmina Mitrevska, Ivanka Ackovska, Jordanco Gjorgiev and Gordana Gigova for their technical help. The professional help of Mr. Lukáš Polena for the estimation of the bimodal distribution curve fitting was also quite beneficial. Special gratitude goes to Prof. Mitko Mladenov, Prof. Suzana Dinevska-Kjovkarovska and Prof. Suzana Nikolovska-Janeva for their support during the present study.

Disclosure statement

The authors declare that they have no competing interests.

The authors report no conflict of interest.