Opioid drugs drive electrical insulation of reward circuitry

Myelin is a fatty substance that forms an insulating sheath around the axons of neurons. In mice, drugs of abuse induce neuronal-activity-regulated changes in the myelination of neurons in the brain’s reward circuitry that release the neurotransmitter chemical dopamine. This myelin plasticity is required for the learning of reward associations with drugs of abuse, such as morphine.