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.

Inclusion Criteria:

• Patient affiliated or entitled to a social security scheme
• Bulimic patients according to DSM-IV TR: minimum 2 bulimic crises (compulsive eating followed by compensatory behavior) / week for 3 weeks
• Patients who signed informed consent to the study
• BMI greater than or equal to 18.5 kg / m²

Exclusion Criteria:

• Against-indication to the SSRI or fluoxetine
• SSRI consumption in the previous three months
• Other addiction (except tobacco, for reasons of feasibility)
• Diagnosis of binge eating disorder or EDNOS (DSM-IV-TR)
• Patients with heart failure
• Against-indication for PET and / or MRI: pacemaker, intracerebral clips, prosthesis made of ferromagnetic material or claustrophobia
• Subjects with suspected pregnancy or in the second half of their menstrual cycle in the absence of oral contraceptives; positive Β-HCG test before the exam