Scientists have determined the problems people with autism have with memory, higher-level thinking, and social interactions may be at least partly caused by the activity of receptors inside brain cells.
Researchers at Washington University School of Medicine in St. Louis said autism experts have long believed the type of receptor in question was a potential contributor to these problems — when located on the surfaces of brain cells. But until now, the role of that receptor — when located inside the cell — was unknown,
Medical Xpress reports.
The receptor, known as the mGlu5 receptor, becomes activated when it binds to the neurotransmitter glutamate, associated with learning and memory. This leads to chain reactions that convert the glutamate's signal into messages traveling inside the cell.
In the new study, scientists working with cells in a dish linked mGlu5 receptors inside cells to processes that turn down the volume at which brain cells talk to each other. These volume changes, essential for learning and memory, may become exaggerated in people with autism.
Pharmaceutical companies have developed therapeutic compounds to decrease signaling associated with the mGlu5 receptor. But the compounds were designed to target mGlu5 surface receptors. In light of the new findings, the scientists question if those drugs will reach the receptors inside cells.
"Our results suggest that to have the greatest therapeutic benefit, we may need to make sure we're blocking all of this type of receptor, both inside and on the surface of the cell," said senior investigator Karen O'Malley, a professor of neurobiology, who helped conduct the study, published in The Journal of Neuroscience.
"The traditional wisdom was that receptors inside the cell were either waiting to go to work on the surface or had just finished working there," said O'Malley. "But when we compared how much of the mGlu5 receptor was on the surface of cells to how much was inside it, we were seeing so much more receptor inside the cell — at least 50 percent, and in some cases as much as 90 percent — that we wondered if the interior receptors had separate functions."
In the last few years, scientists have found that 20 or more types of brain cell receptors located on cell surfaces also are present at high levels inside cells, O'Malley noted.