25.09.2012 - (idw) Julius-Maximilians-Universitt Wrzburg

Many genes are suspected of being involved in the development of attention deficit hyperactivity disorder (ADHD). A Franco-German research group has now examined the role of one of these more closely and discovered clear indications of its complicity. Its scientific name is lphn3. In humans, this gene lies on chromosome 4 and codes the protein latrophilin 3, which may play a role as a synaptic protein and receptor in the brain when the typical characteristics of attention deficit hyperactivity disorder emerge: people affected struggle to focus their attention over longer periods, they are easily distracted, they tire quickly, they often react impulsively, and they demonstrate obvious motor restlessness.

Focus on the latrophilin 3 gene

Latrophilin 3 has long been suspected of being partly responsible for the typical characteristics of ADHD. Though, not all that much is known to date about its role within the physiological processes of the nervous system, says Professor Klaus-Peter Lesch.

Lesch is Chairman of the Department of Molecular Psychiatry and Spokesman for the ADHD Clinical Research Group at the University of Wrzburgs Department of Psychiatry, Psychosomatics, and Psychotherapy. He has had his sights on this protein for a few years now. And he is not alone: Researchers from the USA and Spain have recently shown that a particular variant of the latrophilin 3 gene is frequently found in the genetic material of patients who are still suffering from ADHD in adulthood, says Lesch. What is more, the gene has also been identified as one of a total of 86 risk genes that are suspected of triggering drug dependency. The occurrence of drug dependency is above average in ADHD patients.

Experiments on zebrafish larvae

To improve understanding of the role that latrophilin 3 plays in the development of ADHD symptoms, Lesch and scientists from the Institute of Neurobiology in Gif-sur-Yvette, France, conducted experiments with zebrafish larvae. Zebrafish have now become the standard model in science for examining the genetic fundamentals of brain development and behavior, explains Lesch.

In their experiments, the researchers inhibited the lphn3 gene during a particular development phase and then examined the behavior of the fish larvae. They concentrated primarily on the movement activity of the larvae as an easily measurable expression of motor restlessness.

The results

The outcome: We observed a significant increase in swimming distances and average speed in these fish larvae compared to a control group, write the authors. This effect was also evident during the night-time sleep phases in the same way as human ADHD patients can demonstrate hyperactivity symptoms in their sleep.

See more here:
ADHD: A gene makes fish larvae hyperactive

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