Victims of Parkinson's disease (PD) suffer involuntary body movements that are a side effect from the medication most commonly used to treat the disease. But low-dose lithium, a medication that's been used for years to treat bipolar disorder, can ease the side effects, according to researchers at the Buck Institute for Research on Aging.

The study, which was published in Brain Research, involved mice with Parkinson's that were given Carbidopa/Levodopa, a drug used to boost levels of the neurotransmitter dopamine, which is low in Parkinson's patients. While it's the most effective drug available to manage Parkinson's symptoms, it causes abnormal involuntary movements (AIMS) in 30 percent of patients after four to six years. About 90 percent of patients suffer from AIMS after nine years of using the drug.

"For patients, these side effects are just as devastating as the freezing that is associated with PD," said Buck senior scientist Julie Andersen.

Mice with a human mutation for Parkinson's were given lithium when the mice reached the human age of around 60, the average age of Parkinson's onset in humans. The dosage was the equivalent to about a quarter of what humans receive to treat psychiatric diseases.

Researchers found that lithium boosted the expression of tyrosine hydroxylase, an enzyme that increases the production of dopamine.

"In our mice we saw significant behavioral improvement," said Andersen.

"We clearly saw a prevention of the motor difficulties we would expect to see in the animals," she said. "The treatment also protected the area of the brain that is normally damaged by Parkinson's."

Lithium is a naturally occurring element, not one that is created by scientists like most medications. It was approved by the FDA for the treatment of bipolar disorder in 1970, and is effective for treating mood disorders and suicidal thoughts. Previous studies have suggested that low-dose lithium has a protective effect in other neurodegenerative diseases including Alzheimer's and Huntington's.

Plans for a clinical trial of low-dose lithium to treat Parkinson's patients are in early stages.