By Nancy Deutsch

NEW YORK (Reuters Health) - For the first time, researchers have managed to prove what has long been suspected: people with schizophrenia have receptors in the brain that are chemically overstimulated.

Investigators from Columbia University College of Physicians and Surgeons in New York City have performed the first study in humans to show that the neurochemical dopamine is more active in schizophrenics than in people without the psychiatric disorder.

``We suspected it. This is the first time it's been measured,'' said Dr. Anissa Abi-Dargham, lead author of the study published in the July 5th issue of the Proceedings of the National Academy of Sciences.
　　
　　Measuring the dopamine in the brain is a difficult task, she admitted. The researchers relied on brain imaging scans to assess the dopamine receptors (areas where dopamine attaches) in the brains of 18 people with schizophrenia.

The team performed similar scans on 18 healthy individuals. The percentage of dopamine receptors active in schizophrenics were found to be much higher than in healthy individuals, Abi-Dargham told Reuters Health. Patients with schizophrenia had a dopamine receptor availability of 19%, versus 9% in healthy controls. While the number of individuals in the study was small, these people were not taking any antipsychotic medication at the time, showing that the dopamine receptors were more active without any outside intervention, she said.

When the system regulating dopamine transmission is interrupted, it makes sense that psychotic symptoms would be reduced in these patients, explaining the success of antipsychotics, Abi-Dargham said. These findings show that ''patients with higher levels of dopamine are most likely to improve with antipsychotic treatment,'' she commented. ``It makes sense. It's nice to demonstrate that it makes sense.''

About 20% to 30% of schizophrenic patients do not have high levels of dopamine, she noted, and do not respond to antipsychotic treatment, demonstrating that for some patients, other factors are involved in the disease process. ``We have to find out what it is that would work in other patients.''

Furthermore, the researcher added, in patients with high levels of dopamine, antipsychotics stem the more dramatic symptoms, such as hearing voices. But these people still have altered cognitive functioning and cannot relate well to others, indicating that other processes are involved in schizophrenia, not just dopamine reception, she explained.

The team next plans to conduct a similar study using better imaging equipment that has since become available, Abi-Dargham said. With better tools, they hope to detect changes in smaller structures of the brain.

(From Yahoo)