Circuit-wide gene network analysis reveals sex-specific roles for phosphodiesterase enzymes in cocaine addiction

Cocaine use disorder is a significant public health issue without an effective pharmacological treatment. Successful treatments are hindered in part by an incomplete understanding of the molecular mechanisms in the brain that underly long-lasting maladaptive plasticity and addiction-like behaviors. In this study, we leverage a large RNA-sequencing dataset to generate gene co-expression networks across 6 interconnected regions of the brain's reward circuitry from mice that underwent saline or cocaine self-administration, followed by a 24-hour or 30-day withdrawal period and a saline or cocaine challenge. We identify phosphodiesterase 1b (Pde1b), a Ca2+/calmodulin-dependent enzyme that catalyzes the hydrolysis of cAMP and cGMP, as one of the top hub genes within a nucleus accumbens (NAc) gene module that was bioinformatically associated with addiction-like behavior. Within Drd1- and Drd2-expressing medium spiny neurons (D1 and D2 MSNs) in the NAc, we found that chronic cocaine selectively upregulates Pde1b expression in D2 MSNs. Using a virus-mediated overexpression approach, we demonstrate that Pde1b in the NAc influences cocaine self-administration behavior, locomotor responses, electrophysiological properties of MSNs, and cocaine-induced transcriptomic adaptations in a cell-type- and sex-dependent manner. Together, we identify novel gene modules across the brain's reward circuitry associated with addiction-like behavior and explore the role of Pde1b in regulating the molecular, cellular, and behavioral response to cocaine. Overall design: we overexpressed Pde1b in NAc neurons, injected WT male or female mice with saline or cocaine (20 mg/kg) for 10 days, and performed RNA-seq