Methamphetamine affects a number of the brain’s neurotransmitters, but the most affected is dopamine or the pleasure neurotransmitter. When triggered, dopamine sends pleasure signals to various parts of the body and brain and is then stored for later use. When a person uses meth, an excess of dopamine is released into the brain causing users to feel an excess of pleasure or a high. Unlike normal brain functionality, the dopamine released is not recycled and stored for later, which in turn overstimulates the brain. Instead, it remains in the body until the high is replaced with the crash of unpleasant feelings. In order to replicate that feeling and avoid the crash, users will want more of the drug at higher doses.