[H-3]Paroxetine binding to human peripheral lymphocyte membranes of patients with major depression before and after treatment with fluoxetine

Serotonin has been involved in major depression and is also related to cent ral and peripheral mechanisms of neuroimmunomodulation. Recently, the uptak e of [H-3]serotonin into human peripheral blood lymphocytes has been report ed. We determined the density of serotonin uptake sites by the binding of [ H-3]paroxetine to blood peripheral lymphocyte membrane preparations of cont rols and of patients with major depression before and after treatment with fluoxetine for six weeks. The severity of depression was assessed by the us e of Hamilton Rating Scale for Depression and of Beck Depression Inventory. There was a reduction in the number of sites for [H-3]paroxetine in patien ts before administration of the antidepressant respecting controls, and a r ecovery after the treatment. Affinity was unchanged. No correlation was obt ained between the severity of symptoms determined by Hamilton Rating Scale for Depression or by Beck Depression Inventory, and the number of binding s ites for [H-3]paroxetine. The levels of the plasma serotonin metabolite, 5- hydroxyindoleacetic acid, did not differ between the three groups of subjec ts, but serotonin was lower in patients after treatment respecting controls and in patients before treatment. The significant correlation between spec ific binding of [H-3]paroxetine and plasma serotonin levels in controls was not present in the patients. Lymphocyte serotonin transporter is decreased in major depressed patients and is modulated by antidepressant treatment. In addition of counting with a peripheral marker in depression, the study o f serotonin system in lymphocytes might contribute to understand the bi-dir ectional interaction between the nervous and the immune systems. (C) 1999 I nternational Society for Immunopharmacology. Published by Elsevier Science Ltd. All rights reserved.