Final answer:
Cocaine inhibits the reuptake of dopamine at presynaptic neurons, causing an accumulation of dopamine in the synaptic cleft and continuous stimulation of post-synaptic cells. This leads to the 'high' from cocaine use but is quickly followed by a steep drop in dopamine levels, contributing to cravings.
Step-by-step explanation:
When cocaine is introduced into the system, it affects the synaptic transmission by inhibiting the reuptake of dopamine. This blockade occurs at the dopamine transporter sites on the presynaptic neuron, which normally clear dopamine from the synapse. Cocaine's inhibition of dopamine reuptake leads to an accumulation of dopamine in the synaptic cleft. Consequently, this excess dopamine continuously stimulates the post-synaptic cells leading to amplified neuronal firing and the activation of pleasure centers in the brain.
This mechanism is what underlies the euphoric 'high' associated with cocaine use. However, after this stimulatory phase, there is a rapid depletion of dopamine, leaving the user in a desolate state and often leading to further cravings for the drug. Cocaine would be classified as an agonist since it enhances the activity of dopamine by preventing its reuptake.