Peer presence and familiarity as key factors to reduce cocaine intake: An effect mediated by the Subthalamic Nucleus

International audience; Rationale Stimulant use, including cocaine, often occurs in a social context whose influence is important to understand todecrease intake and reduce associated harms. Although the importance of social influence in the context of drug addictionis known, there is a need for studies assessing its neurobiological substrate and for translational research.Objectives Here, we explored the influence of peer presence and familiarity on cocaine intake and its neurobiological basis.Given the regulatory role of the subthalamic nucleus (STN) on cocaine intake and emotions, we investigated its role on suchinfluence of social context on cocaine intake.Methods We first compared cocaine consumption in various conditions (with no peer present or with peers with differentcharacteristics: abstinent peer or drug-taking peer, familiar or not, cocaine-naive or not, dominant or subordinate) in rats(n = 90). Then, with a translational approach, we assessed the influence of the social context (alone, in the group, in a dyadwith familiar or non-familiar peers) on drug intake in human drug users (n = 77).Results The drug consumption was reduced when a peer was present, abstinent, or drug-taking as well, and further dimin-ished when the peer was non-familiar. The presence of a non-familiar and drug-naive peer represents key conditions todiminish cocaine intake. The STN lesion by itself reduced cocaine intake to the level reached in presence of a non-familiarnaive peer and affected social cognition, positioning the STN as one neurobiological substrate of social influence on drugintake. Then, the human study confirmed the beneficial effect of social presence, especially of non-familiar peers.Conclusion Our results indirectly support the use of social interventions and harm reduction strategies and position the STNas a key cerebral structure to mediate these effects.; The presence of a non-familiar and possibly drug-naive peer is the most efficient condition to diminish stimulant intake. Our results indirectly support the use of harm reduction strategies, in particular supervised consumption rooms for stimulant users.