1. Dopamine Transporter Efflux in ADHD
Michelle S. Mazei-Robison, Erica Bowton, Marion Holy, Martin Schmudermaier, Michael Freissmuth, Harald H. Sitte, Aurelio Galli, and Randy D. Blakely
Elevated dopamine efflux through the dopamine transporter may underlie some forms of attention-deficit hyperactivity disorder (ADHD), according to Mazei-Robison et al. The authors identified a mutant form of dopamine transporter in two siblings with ADHD and expressed the mutant and wild-type forms in HEK-293T cells. Although expression levels and dopamine uptake were similar for mutant and wild-type transporters, the mutant transporter exhibited greater dopamine efflux under both basal and depolarized conditions, due to a greater sensitivity to intracellular sodium concentration and a higher affinity for intracellular dopamine. A role for increased dopamine efflux in ADHD was unexpected, because a common treatment for the disease is amphetamine, which also increases efflux through the wild-type transporter. Remarkably, however, amphetamine reduces efflux through the mutant receptor. Although the mutation described is extremely rare, alterations in dopamine efflux through the transporter due to mutations in transporter regulatory proteins may underlie other forms of the disease.
2. Learning-Induced Gray-Matter Plasticity
Janina Boyke, Joenna Driemeyer, Christian Gaser, Christian Bchel, and Arne May
Learning-induced structural changes in the human brain were previously measured in young adults using high-resolution, three-dimensional magnetic resonance imaging and voxel-based morphometry. Boyke et al. have now extended this research to show that such structural changes also occur in older (50- to 67-year-old) adults. As in the previous study, subjects were scanned three times: before learning to juggle, after 3 months of juggling, and after 3 additional months without juggling. Although the older adults did not learn to juggle
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