Highlights of recently published NIDA-supported studies

Tracing NET

Researchers have developed and successfully tested a new tool for studying the neurobiology of depression, attention deficit hyperactivity disorder, and stimulant abuse. Researchers will be able to use the tool, a new radiotracer, to map the location and circulation of a protein that plays a central role in those conditions: the norepinephrine transporter (NET). Drs. Yu-Shin Ding, Jean Logan, and colleagues at Brookhaven National Laboratory screened six molecules to see whether any of them did the things a radiotracer for NET must do: get into the brain, spread to regions of the brain with high concentrations of NET, bind selectively to the protein, and leave the brain in a reasonable amount of time. Of the six, (S,S)-[11C]methylreboxetine (MRB) was by far the best candidate, binding tightly and specifically to NET. The norepinephrine, dopamine, and serotonin transporters are disrupted in depression, attention disorders, and stimulant abuse. Researchers previously developed radiotracers for the dopamine and serotonin transporters; the ability to image all three transporters in the brain will allow researchers to determine the role of each neurochemical in the disorders.
Journal of Neurochemistry 94(2):337-351, 2005. [Abstract]

Controlling College Students' ADHD Symptoms May Protect Them Against Substance Abuse

In a survey of 334 students at a college in the Southeast, those who reported having experienced symptoms of attention deficit hyperactivity disorder (ADHD) during the past 6 months were three times as likely as those whose symptoms were controlled to say they had intensified their smoking, and six times as likely to report increased frequency of abuse of other drugs (besides alcohol and marijuana) during the past year. Of the 76 respondents who said they had been prescribed ADHD medications at some point during their lives, one-quarter said they had abused their medication to get high, and 29 percent said they had given or sold it to someone else. Dr. Himanshu Upadhyaya and colleagues at the Medical University of South Carolina conducted the study. Appropriate treatment of ADHD may reduce college students' risk of drug abuse.
Journal of Child and Adolescent Psychopharmacology 15(5):799-809, 2005. [Abstract]

Exposure to Morphine During Early Adolescence Sensitizes Rats as Adults

A study conducted at Emory University School of Medicine indicates that exposure to morphine during adolescence may increase sensitivity to the drug during adulthood. Drs. Stephen Holtzman and David White first established that both periadolescent (7 to 10 days before puberty onset) and adult male rats receiving 10 mg/kg/day of morphine for 1 day or 3 consecutive days exhibited similar increases in locomotor activity relative to age-matched rats receiving only saline. When the researchers reexposed the animals to morphine 5 weeks later, significant age- and exposure-related differences emerged. All of the rats were more active, but a relatively small dose of morphine (0.3 mg/kg) triggered significantly more activity in the rats that previously were exposed to morphine for 3 days as periadolescents, relative to their 1-day and unexposed counterparts. By contrast, rats previously exposed for 3 days as adults required 10 times that dose to exhibit more activity than those in the 1-day and unexposed groups. The findings suggest that, during adolescence, even a relatively low level of exposure to morphine can have profound, long-lasting effects.
European Journal of Pharmacology 528(1-3):119-123, 2005. [Abstract]

Volume 21, Number 4 (October 2007)