There are indications that methamphetamine now is being manufactured on a larger scale by organized groups operating out of Mexico and southern California. Clandestine labs have produced the drug in rural and desert areas where the telltale odors of the production process are less likely to be detected. Mobile labs in campers and vans have been reported in Washington. A NIDA-funded study in Seattle confirmed that methamphetamine use was widespread among the city's homosexual and bisexual populations. Research has shown that methamphetamine releases high levels of the neurotransmitter dopamine, which stimulates brain cells, causing enhanced mood and increased body movement.
Animal studies show that high doses of methamphetamine damage nerve cells.
In rats, one high dose of methamphetamine is enough to cause damage. Prolonged dosage seems to make it worse. Another major research focus is on methamphetamine's neurotoxicity, specifically its action in damaging brain cells that contain dopamine and serotonin, another neurotransmitter. Scientists think that methamphetamine abuse over time may cause reduced levels of dopamine, which can cause symptoms like those of Parkinson's disease, a severe movement disorder. The damage is essentially permanent, although there may be some regrowth.