From San Diego, at a meeting of the Society for Neuroscience
More than 80 percent of babies born prematurely in the United States develop sleep apnea, a condition in which breathing stops periodically during sleep. New research points to a possible link between sleep apnea and attention-deficit hyperactivity disorder (ADHD), a problem that affects concentration and learning in about 2 million children and adults in the United States.
Michael Decker and his colleagues at Emory University in Atlanta exposed two groups of rat pups ages 7 to 11 days to brief bursts of either normal room air or low-oxygen air. The rats’ ages correspond to 32 to 33 gestational weeks in people, a common time for premature birth.
Once the pups grew up into juvenile rats of about 8 weeks of age, many of those exposed to low-oxygen conditions showed symptoms similar to those of ADHD. For example, these rats were more hyperactive, scored lower on memory tests, and reacted differently to novel situations than did animals that had received room air.
To determine differences in brain chemistry that may have caused such symptoms, Decker’s team inserted probes into the brains of rats in both groups. Compared with their normal-air counterparts, the low-oxygen rats had about 50 percent less dopamine, a brain chemical that regulates pain, pleasure, and emotional responses. Further tests showed that the brains of low-oxygen rats made adequate dopamine but it was kept inside nerve cells instead of being released normally.
Although Decker and his colleagues note that ADHD is a complex disorder linked to genetic factors and environmental toxins, among other possible causes, they predict that further research will elucidate the connection between low dopamine and ADHD symptoms.