Internalization of serotonin 5‐HT 1A autoreceptors as an imaging biomarker of antidepressant response

International audienceSerotonin (5-hydroxytryptamine, 5-HT) and its various receptors are involved in numerous CNS functions. Among the currently known 5-HT receptors, the 5-HT1A receptor is the best characterized subtype. It is tightly implicated in the pathogenesis of mood disorders, notably in depression, and thus represents an important target for drug therapy. Binding to 5-HT1A receptors can be visualized and quantified by positron emission tomography (PET), facilitating the translation from animal research to man. Using the 5-HT1A radiotracer [18F]MPPF, recent PET studies in cat and human have provided evidence that internalization of 5-HT1A autoreceptors is amenable to in vivo neuroimaging at the very onset of specific serotonin reuptake inhibitor (SSRI) administration. The in vivo detection of this phenomenon in human is promising in terms of clinical management, particularly as an early biomarker of responsiveness to SSRI treatment. However, several questions are still pending regarding the correlation between 5-HT1A internalization at the onset of the treatment and the ensuing therapeutic efficac