Final answer:
Cocaine acts as a stimulant by preventing the uptake of dopamine, leading to increased dopamine levels and stimulating the brain's pleasure centers. This explains the 'high' and addictive properties of cocaine.
Step-by-step explanation:
Cocaine acts as a stimulant by preventing nerve cells from taking up dopamine, another neurotransmitter, from the synapse. High levels of dopamine are therefore available to stimulate the pleasure centers of the brain. The enhancement of dopamine action is thought to be responsible for cocaine's "high" and its addictive properties.
After the binge, dopamine is depleted in less than an hour. This leaves the user in a pleasureless state and (often) craving more cocaine.