Hockenbury Discovering Psychology 5th txtbk

Psychoactive Drugs173Using any type of amphetamines for an extended period oftime is followed by “crashing”—withdrawal symptoms of fatigue,deep sleep, intense mental depression, and increased appetite.This is another example of a drug rebound effect. Users also becomepsychologically dependent on the drug for the euphoricstate, or “rush,” that it produces, especially when injected.Benzedrine and dexedrine are prescription amphetamines.Methamphetamine, also known as meth, is an illegal drug that canbe easily manufactured in home or street laboratories. Providingan intense high that is longer-lasting and less expensive than thatof cocaine, methamphetamine use has spread from the westernUnited States to the rest of the country, including small towns inthe rural Midwest and South.Methamphetamine is highly addictive and can cause extensivebrain damage and tissue loss, as discussed in the Focus onNeuroscience titled “How Methamphetamines Erode the Brain.” Even after months ofabstinence, PET scans of former meth users showed significant reductions in the numberof dopamine receptors and dopamine transporters (Volkow & others, 2001a).Dopamine transporters play a critical role in removing dopamine from the synaptic gapbetween neurons, then transporting it back to the dopamine-producing neurons.What are the behavioral effects of losing dopamine receptors and transporters?Memory and motor skill problems are common in former abusers. Numerous studieshave shown that the most severe deficits occurred in those with the greatest lossof dopamine transporters (Chang & others, 2008; Tomasi & others, 2007a, 2007b;Volkow & others, 2001b). Extensive neurological damage, especially to the frontallobes, adds to the cognitive and social skill deficits that are evident in heavymethamphetamine users (Homer & others, 2008). Depression, emotional instability,and impulsive and violent behavior are also common. Finally, recent researchsuggests that it may take years for the brain to recover from damage caused bymethamphetamine abuse (Bamford & others, 2008).Cocaine is an illegal stimulant derived from the leaves of the coca plant, which isfound in South America. (The coca plant is not the source of cocoa or chocolate,which is made from the beans of the cacao tree.) Psychologically, cocaine producesintense euphoria, mental alertness, and self-confidence. These psychological responsesoccur because cocaine blocks the reuptake of three different neurotransmitters—dopamine,serotonin, and norepinephrine. Blocking reuptake potentiates orincreases the effects of these neurotransmitters.Cocaine Toothache Drops? Prior to 1914,cocaine was legal in the United States and,like the opiates, was widely used as aningredient in over-the-counter medicines(Jonnes, 1999). From this 1885 advertisementfor Cocaine Toothache Drops, it’sclear that cocaine was used to treat childrenas well as adults. Cocaine derivatives,such as novocaine and lidocaine, are stillused medically as anesthetics. Cocaine wasalso part of Coca-Cola’s original formula in1888. It was replaced in 1903 with anotherstimulant, caffeine. Coca leaves, with thecocaine extracted for medical purposes,are still used for flavoring cola drinks.FOCUS ON NEUROSCIENCEHow Methamphetamines Erode the BrainResearcher Paul Thompson and his colleagues (2004) used MRIscans to compare the brains of chronic methamphetamine usersto those of healthy adults. In the composite scan shown here,red indicates areas with tissue loss from 5 to 10 percent.Green indicates 3 to 5 percent tissue loss, and blue indicatesrelatively intact brain regions. Thompson foundthat meth abusers experienced up to 10 percent tissueloss in limbic system areas involved in emotion andreward. Significant tissue loss also occurred in hippocampalregions involved in learning and memory.“We expected some brain changes, but we didn’t expectso much brain tissue to be destroyed,” Thompsonsaid. Not surprisingly, methamphetamine abusersperformed more poorly on memory tests as compared tohealthy people the same age (Thompson & others, 2004).Areas of Greatest LossEmotion, reward(limbic system)Memory(hippocampus)