Opposing mechanisms mediate morphine- and cocaine-induced generation of silent synapses

Cocaine and morphine produce similar addiction-related behaviors, but different adaptations at accumbens synapses. The authors explain this paradox, showing that both drugs generate silent synapses in distinct neuronal types: cocaine in D1 type and morphine in D2 type. Withdrawal strengthens cocaine-generated silent synapses and weakens morphine-generated ones, producing common circuit effects.