The medial orbitofrontal cortex (mOFC) regulates a variety of cognitive functions, including refining action selection involving reward uncertainty. This region sends projections to numerous subcortical targets, including the ventral and dorsal striatum, yet how these cortico-striatal circuits differentially regulate risk/reward decision making is unknown. The present study examined the contribution of mOFC circuits linking the nucleus accumbens (NAc) and dorsomedial striatum (DMS) to risk/reward decision making using pharmacological disconnections. Male rats were well-trained on a probabilistic discounting task involving choice between small/certain or large/risky rewards, with the probability of obtaining the larger reward decreasing or increasing over a session. Disconnection of mOFC-striatal pathways was achieved using infusions GABA agonists inactivating the mOFC in one hemisphere, combined with NAc or DMS inactivation in the contra- or ipsilateral hemisphere. Perturbing mOFC→NAc circuits induced sub-...