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

Abstract 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 .