Noradrenaline: the brain chemical that helps us stop
13 February 2006
A team of Cambridge scientists have shown for the first time that the ability to stop ourselves doing inappropriate actions, like blurting out impulsive comments, jumping red lights, or rushing in front of cars is controlled by the brain chemical noradrenaline. The discovery has important implications for the development of drug treatments for conditions such as attention deficit hyperactivity disorder (ADHD)
Scientists Samuel Chamberlain, MRC researcher and student doctor at the University of Cambridge School of Clinical Medicine, and Barbara Sahakian, Professor of Clinical Neuropsychology at Cambridge University and member of the Behavioural and Clinical Neurosciences Institute, funded by a joint grant from the Medical Research Council and the Wellcome Trust showed that increasing a brain chemical called noradrenaline by giving the drug atomoxetine made healthy volunteers better at stopping or inhibiting their actions. The findings are published in Science this week: Neurochemical Modulation of Response Inhibition and Probabilistic Learning in Humans (PDF 128k)
The research team used a computerised test that involved pressing a left or right key as quickly as possible in response to arrows on a computer screen. When a beep noise sounded, this signalled to volunteers that they should stop or inhibit their responses. This is a simplified form of stopping, which can be related to everyday behaviour such as being able to stop at red lights.
Many neuropsychiatric patients, particularly those with ADHD, have difficulties inhibiting their inappropriate behaviours. Atomoxetine, which was licensed for the treatment of ADHD in 2004, works by increasing noradrenaline. The Cambridge group believes that their study sheds light on the mechanism of action of the drug in the clinical treatment of impulsive behaviour in ADHD.
Although literature had suggested that another brain chemical, serotonin, might be important in this form of impulsive behaviour, the other key finding of the Science paper was that this was not the case.
Lead author Dr Samuel Chamberlain said, “These results are important because difficulties stopping inappropriate behaviour cause some of the greatest problems for patients with ADHD and their families.”
Professor Barbara Sahakian said, “We think that this is a key discovery, because understanding how this drug acts to produce impulse control will allow us to develop more effective treatments for patients showing impulsive behaviour.”
