Their report in the Journal of Neurophysiology helps explain how a stimulant aids people with attention deficit and hyperactivity disorders to improve their focus without increasing their motor activity. Methylphenidate, prescribed under the brand name Ritalin, has been used for more than 20 years, mostly in children, to treat attention deficit hyperactivity disorder (ADHD) and attention deficit disorder (ADD). The drug can also help people who don't suffer either disorder to attend better to a cognitive task.

Despite its wide use, little is known about how the drug, a chemical cousin of amphetamines, produces its therapeutic effects. Researchers want to unlock the mystery of why the drug has the paradoxical effect of decreasing hyperactive behavior and increasing the ability to focus, even though it is a stimulant, said Barry Waterhouse, the study's senior author.

"We're developing a series of behavioral and electrophysiological assays for examining the actions of drugs like methylphenidate," Waterhouse said. "If we can show exactly how methylphenidate works, we may be able to produce even more effective drugs and provide a better understanding of the physiology underlying ADHD."

The study, using rats, is the first to document the increase in norepinephrine and suppression of the neuronal response in this sensory pathway of the brain. "Methylphenidate enhances noradrenergic transmission and suppresses mid- and long-latency sensory responses in the primary somatosensory cortex of awake rats," by Philadelphia-based researchers Candice Drouin, University of Pennsylvania; Michelle Page, Thomas Jefferson University; and Barry Waterhouse, Drexel Univ
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30-May-2006