The termination or serotoninergic neurotransmission is accomplished by rapid uptake or the released 5-HT by serotonin transporter (5-HTT). Activity 5-HIT is regulated by kinase C and phosphatase 2A. Changes in peripheral and central activity of 5-HIT (its uptake kinetic, Vmax and Km) are intensively studied. Many reports show modification in the binding of platelet presynaptic 5-HT uptake sites in psychiatric illnesses (with [3H]imipramine, [3H]paroxetine, [3H]citalopram used as ligands). This papers reviews some of the most important data from this field of research.