Final answer:
An agonist is a drug that acts like the endogenous neurotransmitter by binding to its receptor, while antagonist blocks or closes the channel, inhibiting the normal activity of the neurotransmitter. Cocaine impairs the reuptake of dopamine and causes more dopamine to be released into the synaptic cleft, making it an agonist.
Step-by-step explanation:
An agonist is a drug that acts like the endogenous neurotransmitter by binding to its receptor. It stimulates the receptor and produces a similar effect to the neurotransmitter. On the other hand, an antagonist is a drug that binds to the same receptor but blocks or closes the channel, thereby inhibiting the normal activity of the neurotransmitter.
For example, cocaine impairs the reuptake of dopamine and causes more dopamine to be released into the synaptic cleft. Therefore, cocaine would be classified as an agonist because it mimics the effects of dopamine by increasing its concentration in the synapse.