How do drugs work in the brain to produce pleasure?

All drugs of abuse directly or indirectly target the brain’s reward system by flooding the circuit with dopamine. Dopamine is a neurotransmitter present in regions of the brain that regulate movement, emotion, cognition, motivation, and feelings of pleasure. The overstimulation of this system, which rewards our natural, life-sustaining behaviors, produces the euphoric effects sought by people who abuse drugs and teaches them to repeat the behavior.