Evaluation of the Efficacy of Serotoninergic Antidepressants in Bulimia Nervosa, According to Brain Serotonin Profile Determined by Positron Emission Tomography With [18F] MPPF.

Bulimia nervosa (BN) is a serious mental illness characterized by massive food crises followed by anxiety and compensatory behaviours (vomiting more often). Recent data show an increasing prevalence and a serious prognosis, due to excess mortality by suicide but also somatic complications.

Two types of treatments are validated : serotoninergic antidepressants (SSRI) and psychotherapy. Many clinical trials confirm the effectiveness of the SSRI. But many studies also emphasize the important proportion of non-responders to SSRI, few of them analyze the reasons for this non-answer.

To better understand the mode of action of SSRI, we should analyse the serotonergic activity in the central nervous system in bulimia. Recently, specific brain 5HT1A serotonin receptor ligands ([18F] MPPF or [11 C] WAY-100635), were used in positron emission tomography (PET) to characterize the serotonergic abnormalities of bulimic patients. The ligand [18F] MPPF has the feature to be sensitive to the level of endogenous serotonin.

A first pilot study using PET with [18F] MPPF realized between the University Hospital of Saint Etienne and Lyon CERMEP showed a diffuse increase of the binding potential of [18F] MPPF in bulimic patients, suggesting a decrease in serotonin activity.

The brain regions affected were angular gyrus, medial frontal cortex, left insula, cingulate gyrus and orbitofrontal gyrus. These areas are involved in major bulimic symptoms (impulse, taste, instinct, anxiety and satiety). However, we noticed an interindividual heterogeneity of cortical binding of [18F] MPPF.

In front of the heterogeneity in terms of efficacity of SSRI and brain serotoninergic activity, it seems necessary to continues investigations, to determine if there is a link between brain serotonin profile and responding to SSRI in bulimia nervosa.