All drugs change the way the brain works by changing the way nerve cells communicate. Nerve cells, called neurons, send messages to each other by releasing chemicals called neurotransmitters. These neurotransmitters attach to molecules on neurons called receptors. (Learn more about how neurotransmitters work.) Drugs affect this signaling process.
There are many neurotransmitters, but dopamine is the main one that makes people feel good when they do something they enjoy, like eating a piece of chocolate cake or playing a video game. Normally, dopamine gets recycled back into the cell that released it, thus shutting off the signal. Stimulants like cocaine prevent the dopamine from being recycled, causing a buildup of the neurotransmitter in the brain. It is this flood of dopamine that reinforces taking cocaine, “training” the brain to repeat the behavior. The drug can cause a feeling of intense pleasure and increased energy.
With repeated use, stimulants like cocaine can disrupt how the brain’s dopamine system works, reducing a person’s ability to feel pleasure from normal, everyday activities. People will often develop tolerance, which means they must take more of the drug to get the desired effect. If a person becomes addicted, they might take the drug just to feel “normal.”
After the "high" of the cocaine wears off, many people experience a "crash" and feel tired or sad for days. They also experience a strong craving to take cocaine again to try to feel better.
Learn more about how the brain works and what happens when a person uses drugs. And, check out how the brain responds to natural rewards and to drugs.