Balance between direct and indirect pathways of the nucleus accumbens controls social behavior in mice

Background: Deficient social interactions are a hallmark of major neuropsychiatric disorders, and cumulating evidence point to altered social reward and motivation as key underlying mechanisms in these pathologies. In the present study, we aimed at assessing the role of the two striatal projecting neuronal (SPN) populations bearing either D1R or D2R dopamine receptors (D1R- and D2R-SPNs), in modulating social behavior and other behaviors often altered in neuropsychiatric disorders. Methods: We selectively ablated D1R- and D2R-SPNs using an inducible diphtheria toxin receptor (DTR)-mediated cell targeting strategy and assessed social behavior as well as repetitive/perseverative behavior, motor function and anxiety levels. We tested the effects of optogenetic stimulation of D2R-SPNs in the Nucleus Accumbens (NAc) and pharmacological compounds repressing D2R-SPN. Results: Targeted deletion of D1R-SPNs in the NAc blunted social behavior in mice, facilitated skill motor learning and increased anxiety levels. These behaviors were normalized by pharmacological inhibition of D2R-SPN, which also repressed transcription in the efferent nucleus, the ventral pallidum (VP). In contrast, ablation of D1R-SPNs in the dorsal striatum had no impact on social behavior, impaired motor skill learning, and decreased anxiety levels. Deletion of D2R-SPNs in the NAc also produced motor stereotypies but facilitated social behavior and impaired skill motor learning. We mimicked excessive D2R-SPN activity by optically stimulating D2R-SPNs in the NAc and evidenced a severe deficit in social interaction that was prevented by D2R-SPN pharmacological inhibition. Conclusions: Repressing D2R-SPN activity may represent a promising therapeutic strategy to relieve social deficit in neuropsychiatric disorders. ### Competing Interest Statement The authors have declared no competing interest.