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PET Can Take the Mystery Out of Addictions (and More)
Study the brains of alcohol-addicted people: the number of GABA receptors, which damp nerve activity in the brain, are truly winnowed down. Or, like Betsy McCaul, match brains of men and women on amphetamines and learn, surprisingly, that they give men a flood of rewarding dopamine.
It’s clear that positron emission tomography is addictions research’s indispensable friend.
For some time, psychiatrists have known that PET scans could clarify the biology behind abnormal behavior. Yet the technique’s reliance on decaying radioactive compounds as tracers—you need a cyclotron in your basement to make them—a scanner’s expense and the need for specialists to interpret its signals may have kept use down. Hopkins, however, is an exception, says radiology professor Dean Wong: “PET studies have long been a staple of research here. Both use and expertise run high.” Wong, who has a psychiatry appointment, was part of the first team to map dopamine receptors in living brains.
Now a new PET scanner—a high-resolution research tomograph—is making psychiatric biology studies easier. The device nearly triples the accuracy of existing machines. Already, psychiatry research has booked half of the scanner’s operating time.
Radiologically, PET is as versatile as a Veg-O-Matic. Scans can reflect metabolism of brain areas—“the easy stuff,” Wong says. More sophisticated are the ligand-based studies that Hopkins pioneered, ones that temporarily link tracers with proteins on cell surfaces. They can map the density and distribution of serotonin, opiate and other brain receptors. Give certain addicted patients single, tiny doses of alcohol and watch dopamine neurons light up.
PET is helping to uncover biological subtypes in alcoholism and other addictions, not to mention schizophrenia, bipolar and other diseases. And of interest to pharma companies, it can determine useful dosages of potential new therapies, not to mention show, visually, if they’re working.