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Differences in the dynamics of changes in the concentration of kynurenic acid in the blood serum of depressed patients treated with electroconvulsive therapy.

BACKGROUND
Nowadays, depression is a serious clinical problem, as the prevalence of its various forms increases and there are growing numbers of patients with severe forms of depression and treatment-refractory depression. Depressed patients have been observed to have decreased levels of kynurenic acid (KYNA), which is the only endogenous antagonist of ionotropic N-methyl-D-aspartate (NMDA) receptors. The aim of this study was to identify subgroups of patients differing in the dynamics of changes in KYNA concentration during electroconvulsive therapy (ECT).


SUBJECTS AND METHODS
The study included 32 patients with an ICD-10 diagnosis of a major depressive episode receiving ECT treatment and 48 healthy volunteers. Blood serum KYNA concentrations were determined using HPLC-based methods, and clinical assessment was performed using the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Clinical Global Impressions (CGI) Scale.


RESULTS
Three subgroups of patients with depression were identified which differed in baseline KYNA levels and in the dynamics of changes in blood serum KYNA concentrations during and after ECT.


CONCLUSIONS
The largest number of patients with clinical improvement (83%) was observed in the subgroup with significantly lower pre-treatment, treatment and post-treatment KYNA concentrations than those determined in the control group. This subgroup of patients also showed the lowest dynamics of changes in KYNA concentrations during ECT. Clinical improvement was observed in 75% of depressed patients who had insignificantly lower pre-treatment levels of KYNA and slightly higher levels of this acid after 6 and 12 ECT sessions than controls. The smallest number of patients with clinical improvement (50%) was observed in the subgroup of patients who had similar pre-treatment and treatment concentrations of KYNA to controls and whose post-treatment concentrations of KYNA were significantly lower than those of healthy individuals.