Nerve cells, called neurons, send messages to each other by releasing special chemicals called neurotransmitters. Neurotransmitters are able to work by attaching to key sites on neurons called receptors. One of the neurotransmitters affected by cocaine is called dopamine. Normally, once dopamine has attached to a nerve cell's receptor and caused a change in the cell, it's pumped back to the neuron that released it. But cocaine blocks the pump, called the dopamine transporter.
Dopamine then builds up in the gap synapse between neurons.
That's why someone who uses cocaine feels an extra sense of pleasure for a short time. Although cocaine may make someone feel pleasure for a while, later it can damage the ability to feel pleasure. Research suggests that long-term cocaine use may reduce the amount of dopamine or the number of dopamine receptors in the brain. When this happens, nerve cells must have cocaine to communicate properly. Without the drug, the brain can't send enough dopamine into the receptors to create a feeling of pleasure.