Intestinal protein may have role in ADHD, other neurological disorders

A biochemical pathway long associated with diarrhea and intestinal function may provide a new therapeutic target for treating ADHD (Attention Deficit Hyperactivity Disorder) other neuropsychiatric disorders, according to a team of scientists from China and the United States reporting Aug. 11 in Science.

Scientists have for the last quarter century studied the intestinal protein, guanylyl cyclase-C (GC-C) for its role in diarrheal disease and other intestinal functions, according to Mitchell Cohen, M.D., U.S. author on the study and director of Gastroenterology, Hepatology and Nutrition at Cincinnati Children's Hospital Medical Center. In fact, it had been thought that GC-C was found primarily in the intestine.

In the current study, scientists in China who collaborated with Dr. Cohen discovered that the receptor is also expressed in critical areas of the brain. The senior author on the study is Dr. Minmin Luo, a researcher at the National Institute of Biological Sciences and Tsinghua University in Beijing.

Using a mouse model developed in Dr. Ralph Giannella's laboratory at the University of Cincinnati, in which the GC-C receptor is deleted, or knocked out, the researchers found the mice exhibit hyperactivity and attention deficits. It is the first time that GC-C has been linked to , according to the researchers.

"We show that the neurons selectively express GC-C and that its activation amplifies the excitatory responses mediated by other receptors on dopamine neurons in the midbrain," said Dr. Luo. "Working through a protein kinase called PKG, GC-C activity increases brain dopamine levels and thus regulate mouse attention and activity level."

When the researchers treated the GC-C with amphetamine-based ADHD medication and a PKG activator, it reversed their hyperactive, inattentive behavior.

"The results indicate important behavioral and physiological functions for the GC-C/PKG signaling pathway in the brain," said Dr. Luo. "The data also suggest new therapeutic targets for neuropsychiatric disorders related to malfunctions of midbrain dopamine receptors."

One of the most prevalent human behavioral disorders, ADHD has been linked to imbalances in the dopamine system. The researchers noted in the study that its findings – mice exhibiting reduced dopamine levels and related behavioral problems – are consistent with the biochemical characteristics of human ADHD.

"This could make the GC-C knockout mouse a good research model for ADHD and other behavioral disorders," said Dr. Cohen. "Efforts to develop activators or inhibitors of the GC-C/PKG signaling pathway may lead to novel treatments for other disorders, such schizophrenia, Parkinson's disease and addiction."

Related Stories

Adult ADHD linked with dopamine levels

Aug 09, 2007

Adults with attention-deficit/hyperactivity disorder have a reduced response to the drug Ritalin, U.S. government scientists have found.

Protein on 'speed' linked to ADHD

Jul 08, 2008

A genetic change in the dopamine transporter – one of the brain's dopamine-handling proteins – makes it behave as if amphetamine is present and "run backward," Vanderbilt University Medical Center investigators report ...

Recommended for you

Smoking while pregnant linked to ADHD in children

Jul 22, 2014

(HealthDay)—Children born to women who smoked during pregnancy appear to have an increased risk of developing attention-deficit/hyperactivity disorder (ADHD), according to new research.

Validity of change in DSM-5 ADHD age of onset criterion confirmed

Jul 14, 2014

A recent study published in the July 2014 issue of the Journal of the American Academy of Child and Adolescent Psychiatry confirms the validity of the DSM-5 change to the age of onset criterion for diagnosis of attention-deficit/hyperactivity disord ...

User comments