Oxytocin (OT) is increasingly studied for its therapeutic potential in psychiatric disorders, which are associated with the deregulation of several neurotransmission systems. Studies in rodents demonstrated that the interaction between OT and serotonin (5-HT) is critical for several aspects of social behavior. Using PET scan in humans, we have recently found that 5-HT 1A receptor (5-HT 1A R) function is modified after intranasal oxytocin intake. However, the underlying mechanism between OT and 5-HT remains unclear. To understand this interaction, we tested 3 male macaque monkeys using both

PET imaging studies using 5-HT 1A receptor radiotracers show a decreased density of this receptor in hippocampi of patients with Alzheimer's disease (AD) at advanced stages. However, current 5-HT 1A receptor radiopharmaceuticals used in neuroimaging are antagonists, thought to bind to 5-HT 1A receptors in different functional states (i.e., both the one which displays high affinity for agonists and is thought to mediate receptor activation, as well as the state which has low affinity for agonists).Comparing the PET imaging obtained using an agonist radiotracer, which binds selectively to functional receptors, with the PET imaging obtained using an antagonist radiotracer would therefore provide original information on 5-HT 1A receptor impairment during AD. Quantitative autoradiography using [