Platelet serotonin uptake in drug-naive depressive patients before and after treatment with citalopram

We investigated the kinetic parameters of serotonin (5-HT) uptake into platelets in a group of 26 drug-naive patients suffering from major depression before and after 3-7 weeks of treatment with citalopram. The degree of depression was rated using the Hamilton Depression Rating Scale (HDRS). The 5-HT uptake characteristics in untreated depressive patients were not significantly different from those of normal subjects. The apparent Michaelis constant (K-M) was significantly increased, the apparent maximal velocity (V-max) was not different from baseline, and the uptake efficiency (V-max/K-M) was significantly decreased after citalopram treatment. A significantly positive correlation between K-M and V-max was found in all groups. There was a significantly lower V-max and V-max/K-M in the female compared with the male depressed patients before citalopram treatment; a hypothesis was supported that lowered 5-HT uptake may reflect a gender-linked vulnerability to a serotonin-related depression. A significant negative correlation between 5-HT uptake efficiency and the initial HDRS score suggests that platelet 5-HT uptake can be used as a marker of effective depressive disorder pharmacotherapy. The initial severity of depression was significantly negatively correlated with V-max, which supported a hypothesis that the initial severity of depressive disorder could be related to the lower V-max. (c) 2007 Elsevier Ireland Ltd. All rights reserved.