Final answer:
A drug that has a molecular structure similar to the body's own neurotransmitter is called an agonist.
Step-by-step explanation:
A drug that has a molecular structure similar to the body's own neurotransmitter is called an agonist. An agonist functions by binding to and activating the same receptor sites as the neurotransmitter, mimicking its effects. This can enhance or stimulate the activity of the neurotransmitter.
Learn more about neurotransmitters