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March 01, 2006

Genes and Amphetamine

Individuals who inherit a particular variant of the DAT1 gene from both parents may have a degree of innate protection against becoming chronic abusers of amphetamine or other stimulants, new research suggests. In a study by Dr. Harriet de Wit and colleagues at the University of Chicago, eight volunteers who carried two copies of the "9-repeat" variant of the gene reported feeling little different following oral administration of amphetamine than after placebo. In contrast, 88 individuals with either one or no "9-repeats" tended to experience the euphoric reaction that is a motivator for stimulant abuse, as well as elevated blood pressure and anxiety. The likely biological basis for the different reactions is that the DAT1 gene affects expression of the dopamine transporter, one of the sites where stimulant drugs exert their pharmacological effects. The researchers note that along with its protective advantage against drug abuse, the 9/9 may have a downside: less benefit from stimulant medications, such as those prescribed for attention deficit hyperactivity disorder. Neuropsychopharmacology 30(3):602-609, 2005.

Brain Recovery in Meth Abusers

Long-term methamphetamine abusers who abstain from the drug for more than a year show signs of structural and functional recovery of nerve cells in a brain region associated with emotion and cognition. Although some chemical signs of cell damage continued after a year of abstinence, some metabolic indicators in the anterior cingulate cortex appeared to return to normal. Using a brain-imaging technique called proton magnetic resonance spectroscopy, Dr. Thomas Nordahl and colleagues at the University of California, Davis found that methamphetamine-addicted men and women showed abnormal metabolite ratios—chemical patterns that can indicate either healthy activity or injury of brain cells. Those who had initiated abstinence in the past 6 months showed some damage-related patterns that were absent in those who had not taken the drug for more than a year and in nonabusers. Patterns reflecting healthy brain activity increased with the duration of abstinence. Archives of General Psychiatry 62(4):444-452, 2005.

New Tools for Studying Inhalant Abuse

Two teams of researchers have developed new tools for investigating the phases and effects of inhalant abuse. Dr. Edwin Zvartau and colleagues at the Pavlov Medical University in Russia, working with Dr. Robert Balster of Virginia Commonwealth University, devised a promising method for mice to self-administer solvents that are abused by humans via inhalation. The new procedure circumvents technical difficulties that have prevented researchers from performing with inhalants the same types of animal studies that have provided much basic information about the effects of other drugs. Another team, led by Dr. Jean Logan of Brookhaven National Laboratory, successfully tested new chemicals that trace the levels of the inhalants acetone and butane in the brains of baboons. Such tracers allow researchers to monitor the effects of each inhalant on the brain: the time it takes to arrive, the regions affected, and how long it stays. These characteristics influence a substance's potential for abuse in humans and its neurotoxic effects. European Journal of Pharmacology 485(1-3):211-218, 2004; and Nuclear Medicine and Biology 32(2):201-208, 2005.

Weighing Nicotine Replacement

Photo - Postmenopausal woman patient

Postmenopausal women using the nicotine patch gained less weight during their first 2 weeks of abstinence from smoking than women on placebo, even though they consumed more total calories and fat and had the same level of physical activity. In one of the first studies to address the challenges older women face when they try to quit smoking, Dr. Sharon Allen and colleagues at the University of Minnesota also found that the simultaneous use of hormone replacement therapy by participants did not affect the results. One-third of women over age 45 smoke, and researchers are looking for strategies to help them quit. Fear of weight gain can be a serious barrier to quitting, particularly during the menopausal period when women typically gain a few pounds. Addictive Behaviors 30(7):1273-1280, 2005.

Teen Access to Cigarettes Declining, But Still High

Fewer underage teens bought cigarettes in 2002 than in 1997, but most still found the products easy to obtain, according to the Monitoring the Future (MTF) Survey of 8th-, 10th-, and 12th-graders. Half the teens who said they were current smokers reported personally buying cigarettes from a retail store, down about 5 percent from 1997; only one-third said they were asked to provide proof of age during their last purchase. They most often bought cigarettes at gas stations or convenience stores, which have the highest rates of pro-tobacco advertising and self-service access to tobacco products. Dr. Lloyd Johnston and colleagues at the University of Michigan say the findings suggest that some policies to limit access to cigarettes by minors—for example, requiring clerk-assisted purchases—may be having an impact, but also point to considerable retailer noncompliance with underage sales regulations. American Journal of Preventive Medicine 27(4):267-276, 2004.