FRONTAL 5-HT2A RECEPTORS STUDIED IN DEPRESSIVE PATIENTS DURING CHRONIC TREATMENT BY SELECTIVE SEROTONIN REUPTAKE INHIBITORS

To investigate adaptative changes of 5-HT2A receptors induced by SSRIs , six patients chronically treated for a depressive episode (four with fluoxetine, two with fluvoxamine) were studied with PET and [F-18]set operone. They were compared to eight untreated depressive patients. Th e mean frontal to cerebellum radioactivity concentration ratio, an ind ex of the [F-18]setoperone specific binding to 5-HT2A receptors, was h igher in treated than in untreated patients, when age was taken into a ccount. This suggests that chronic treatment by SSRIs could induce an up-regulation of the 5-HT2A receptors, and that 5-HT2A receptor down-r egulation is not a common mechanism for the therapeutic effects of all serotoninergic antidepressive drugs.