But what happens when a person takes a drug?
This image shows how cocaine is able to alter activity in the synapse. Cocaine (shown in green), attaches to dopamine transporters (shown in purple), thereby blocking dopamine from being taken back up by the first neuron. Thus dopamine can continue to stimulate (maybe over-stimulate) the receptors of the second neuron because it remains in the synapse for a longer period of time. This duration of stimulation and amount of dopamine in the synapse is far greater than what normally occurs when a person engages in an enjoyable activity (e.g., eating, sex, etc), and is what produces cocaine’s intense euphoria and potential for abuse.