The Perineuronal Net Protein Brevican Acts in Nucleus Accumbens Parvalbumin-Expressing Interneurons of Adult Mice to Regulate Excitatory Synaptic Inputs and Motivated Behaviors.

BACKGROUND: Experience-dependent functional adaptation of nucleus accumbens (NAc) circuitry underlies the development and expression of reward-motivated behaviors. Parvalbumin-expressing GABAergic (gamma-aminobutyric acidergic) interneurons (PVINs) within the NAc are required for this process. Perineuronal nets (PNNs) are extracellular matrix structures enriched around PVINs that arise during development and have been proposed to mediate brain circuit stability. However, their function in the adult NAc is largely unknown. Here, we studied the developmental emergence and adult regulation of PNNs in the NAc of male and female mice and examined the cellular and behavioral consequences of reducing the PNN component brevican in NAc PVINs. METHODS: We characterized the expression of PNN components in mouse NAc using immunofluorescence and RNA in situ hybridization. We lowered brevican in NAc PVINs of adult mice using an intersectional viral and genetic method and quantified the effects on synaptic inputs to NAc PVINs and reward-motivated learning. RESULTS: PNNs around NAc PVINs were developmentally regulated and appeared during adolescence. In the adult NAc, PVIN PNNs were also dynamically regulated by cocaine. Transcription of the gene that encodes brevican was regulated in a cell type- and isoform-specific manner in the NAc, with the membrane-tethered form of brevican being highly enriched in PVINs. Lowering brevican in NAc PVINs of adult mice decreased their excitatory inputs and enhanced both short-term novel object recognition and cocaine-induced conditioned place preference. CONCLUSIONS: Regulation of brevican in NAc PVINs of adult mice modulates their excitatory synaptic drive and sets experience thresholds for the development of motivated behaviors driven by rewarding stimuli.