HOW OPIOIDS WORK

All substances of abuse ultimately affect the dopamine pathway in the reward center of our brain. Many substances do so through opioid receptors. Opioids boost dopamine levels by stimulating molecules called mu opioid receptors that sit on the surface of certain neurons. Normally, these receptors are activated by hormones and brain chemicals made in the body, such as endorphins (endogenous opioids), to reinforce pleasurable behavior such as eating, having sex or listening to music. A single dose of heroin releases many times the amount of dopamine that is produced by a favorite food or song.