henry copeland:

How Meth Destroys The Body | The Meth Epidemic | FRONTLINE | PBS

"There [are] a whole variety of reasons to try methamphetamine," explains Dr. Richard Rawson, associate director of UCLA's Integrated Substance Abuse Programs. "[H]owever, once they take the drug … their reasons are pretty much the same: They like how it affects their brain[s]." Meth users have described this feeling as a sudden rush of pleasure lasting for several minutes, followed by a euphoric high that lasts between six and 12 hours, and it is the result of drug causing the brain to release excessive amounts of the chemical dopamine, a neurotransmitter that controls pleasure. All drugs of abuse cause the release of dopamine, even alcohol and nicotine, explains Rawson, "[But] methamphetamine produces the mother of all dopamine releases." For example, in lab experiments done on animals, sex causes dopamine levels to jump from 100 to 200 units, and cocaine causes them to spike to 350 units. "[With] methamphetamine you get a release from the base level to about 1,250 units, something that's about 12 times as much of a release of dopamine as you get from food and sex and other pleasurable activities," Rawson says. "This really doesn't occur from any normally rewarding activity. That's one of the reasons why people, when they take methamphetamine, report having this euphoric [feeling] that's unlike anything they've ever experienced." Then, when the drug wears off, users experience profound depression and feel the need to keep taking the drug to avoid the crash.
- www.pbs.org