Methamphetamine exerts its effects on the brain by affecting the activity of three neurotransmitters: dopamine, serotonin, and norepinephrine. Because these neurotransmitters have molecular similarity, drugs like methamphetamine affect the activity of all of these chemical molecules to a degree. These three neurotransmitters belong to a category of chemical compounds called monoamines. The following pages presents information about each of these neurotransmitters. You will learn about the biosynthesis of each neurotransmitter in the brain, the specific brain structures involved in each neurotransmitter system, as well as chemical and behavioral changes that occur because of the effects of methamphetamine use on each neurotransmitter. Below, you will find a pictoral summary of the behaviors that are controlled by dopamine, serotonin, and norepinephrine.