Genes Play Increasing Role in Risk for Tobacco Use Among Women
A generation-spanning study of twins has confirmed that genes and inheritance each play a key role in determining a person's vulnerability to regular tobacco use. For women, the genetic element of their vulnerability to smoking has increased as society's once-strong taboos against tobacco use by women have diminished. Among males, the patterns of tobacco use suggest both genetic and environmental factors account, respectively, for 61 percent and 20 percent of the differences in individuals in their risk for becoming regular users of tobacco. In women born before 1925, rates of tobacco use were low, based largely on environmental factors. For women born since 1940, heritability of tobacco use is essentially the same as in men - 63 percent. The study was conducted by Dr. Kenneth S. Kendler of the Medical College of Virginia (MCV), and researchers at the Karolinska Institute in Stockholm, Sweden. The full article, "Tobacco Consumption in Swedish Twins Reared Apart and Reared Together" appears in the September 2000 issue of the Archives of General Psychiatry (Arch Gen Psychiatry. 2000;57:886-893 (Sept. 2000)). A copy of the article is available from the American Medical Association's Science News Department at 312 464-5374 or on its website at http://archpsyc.ama-assn.org/.
New Study Highlights Addictive Potential of Cocaine
Researchers have found that even casual doses of cocaine can produce chronic changes in brain function that can result in addiction in rhesus monkeys. Over a period of six months of repeated self-administration of low doses of cocaine, neurochemical sensitization to the drug occurred. These changes in dopamine reactivity may represent a neurochemical basis for the tolerance to the effects of cocaine seen in humans, a phenomenon that contributes to increased use of cocaine and binges. The researchers concluded that the observed changes in neurochemical sensitization reinforce the danger of enduring change in brain function from casual cocaine use that can put users at risk of addiction. The lead author of the study was Dr. Charles W. Bradberry, West Haven Veterans Administration Hospital and Yale University School of Medicine. The full article can be found in The Journal of Neuroscience 20(18): 7109-7115 (Sept 5).
Natural Compound May Offer New Treatment for Chronic Pain
An amino acid-like compound that, in animal studies, appears to alleviate chronic pain that cannot be treated with opiates has been identified by researchers. Agmatine, a natural compound synthesized in the brain, also appears to prevent or reverse changes that follow injury to the spinal cord and peripheral nerve cells. Scientists link the processes that govern pain and pain relief to the processes involved in the development of tolerance and addiction to pain-relieving drugs. Understanding the role of agmatine in these processes could be an important step toward improving treatment of pain without drugs such as morphine and toward relieving chronic pain for which no treatment now exists. Agmatine decreased sensitivity to pain accompanying neuropathy and inflammation. In models of neuropathic pain, but not inflammatory pain, agmatine-mediated relief of hypersensitivity appeared to be permanent, unlike the temporary pain relief provided by analgesics like morphine. Scientists found that agmatine also reversed or prevented changes that occur in nerve cells as a result of chronic pain or in the early stages of progression of spinal cord injury. The study was conducted by Dr. Carolyn Fairbanks and Dr. George Wilcox at the University of Minnesota, and colleagues at the University of Miami, Cornell University Medical College, and the East Carolina University School of Medicine. The complete article appears in the September issue of the Proceedings of the National Academy of Science.
Nicotine May Negatively Affect Nonsmokers
In a recent study, researchers found that nicotine administered to nonsmokers increased the rate of response and decreased the response time on work memory (digit recall). However, nicotine decreased accuracy on visual scanning and attention (two-letter search) and impaired gross motor coordination (circular lights). Nicotine also produced dose-related increases in volunteers' reports of negative mood, including tension, anxiety, nervousness, turning of stomach, and sedation. Although tolerance developed to some of the adverse effects of nicotine, performance enhancement was not observed. The study was conducted at NIDA's Intramural Research Program in Baltimore, Maryland, by Dr. Stephen J. Heishman, and Dr. Jack E. Henningfield, Johns Hopkins University School of Medicine. The article appears in the online edition of Psychopharmacology 152(3).