Pubdate: Fri, 26 Mar 1999 Source: Reuters Copyright: 1999 Reuters Limited.


WASHINGTON (Reuters) - A marijuana-like chemical in the brain that helps regulate body movement and coordination might be used to treat diseases that produce tics and shaking, such as Parkinson's disease and schizophrenia, researchers said.

University of California Irvine researchers found that the chemical, known as anandamide, acts as a kind of brake on neural activity in the brains of rats, and might be used to treat the side-effects of diseases that cause uncontrollable movements.

Writing in the April issue of the journal Nature Neuroscience, they said anandamide interferes with the effects of nerve cells that transmit dopamine, the message-carrying chemical responsible for stimulating movement and other motor behavior in the brain.

Uncontrolled production of dopamine has been blamed for some of the symptoms of schizophrenia and the nervous tics and outbursts associated with Tourette's syndrome. A lack of dopamine is blamed for the shaking and motor hesitation that marks Parkinson's disease.

``This shows for the first time how anandamides work in the brain to produce normal motor activity,'' Daniele Piomelli, an associate professor of pharmacology at UCI who helped lead the study, said in a statement.

``Patients with schizophrenia and other diseases have reported that marijuana appears to relieve some of their symptoms, but scientists have never found a physiological reason why. By understanding how the anandamide system works similarly to marijuana, we can explore new ways to treat these diseases more effectively.''

But Piomelli said cannabis itself did not offer any kind of cure. ``Marijuana doesn't provide the regulatory effects on dopamine in the brain that we're looking for,'' he said.

Anandamide, named after the Sanskrit word for ``bliss and tranquillity,'' is used by a network of nerve cells in an area of the brain called the striatum, which coordinates body movements and other motor behavior, the researchers said.

Normally nerve cells regulate this behavior by releasing anandamides at the same time they release dopamine. The anandamides bind to cannabinoid receptors, which are where tetrahydrocannabinol (THC), the active ingredient in marijuana, docks onto cells.

When the team blocked these receptors, rats experienced severe nervous tics and other uncontrolled motor activity.

Piomelli said new drugs that mimic the effects of anandamides could offer gentler treatments for some diseases.

``Current drugs certainly halt the actions of dopamine, but the side effects, including sedation and dizziness, are very severe,'' he said.

In a commentary, David Self of Yale University said the approach could be used to develop drugs that help Parkinson's treatments, which try to boost production of dopamine in the brain but whose effects wear off after a few years.

Drugs that stimulate the cannabinoid receptor might also be used against Huntington's disease, a fatal and incurable disease first marked by jerks and spasms, Self added.