Answer: Cocaine is a dopamine, serotonin, and norepinephrine reuptake inhibitor.
When a neurotransmitter is released into the synaptic space, it can act at a postsynaptic receptor protein. The neurotransmitter can bind to and unbind from these receptors following the rules of Brownian motion. As long as the neurotransmitter is bound, the postsynaptic signal persists.
For the signal to end, the neurotransmitter must be cleared from the synaptic cleft. Some neurotransmitters such as acetylcholine are rapidly degraded by the enzyme acetylcholinesterase.
Instead of being degraded by enzymes, monoamine neurotransmitters such as dopamine, serotonin, and norepinephrine generally get taken back up into the presynaptic cleft. They are shuttled into the cell by a transmembrane protein called a transporter.
The transporter proteins are specific for the neurotransmitter: DAT for dopamine, SERT for serotonin, and NET for norepinephrine.
Cocaine also has action as an inhibitor of voltage-gated sodium channels. Historically, it had been used as an anesthetic during surgery until lidocaine was developed. Currently, cocaine is still used in some surgical procedures for it’s combination of pain inhibiting capability and vasoconstrictive properties.
Cocaine is rewarding because it enhances the signaling of dopamine at the ventral tegmental area - nucleus accumbens synapse, which is believed to play an important role in mediating reward.