Because it is similar to dopamine, Methamphetamine can change the function of any neuron that contains dopamine. And if this weren't enough, Methamphetamine can also affect neurons that contain two other neurotransmitters called serotonin and norepinephrine. All of this means that Methamphetamine can change how lots of things in the brain and the body work. Even small amounts of Methamphetamine can cause a person to be more awake and active, lose their appetite, and become irritable and aggressive. Methamphetamine also causes a person's blood pressure to increase and their heart to beat faster.