Drugs that address an imbalance between the primary neurotransmitters dopamine and acetylcholine. Parkinson disease is caused by an imbalance of the two neurotransmitters responsible for transmitting nerve impulses from the brain to the muscles. One group of anti-Parkinson drugs works by stimulating production of dopamine in the brain, sup¬ plying the substance from which it is formed (levodopa) to be converted to dopamine in the brain. Dopamine levels can also be increased by reducing the breakdown of dopamine in the brain or by stimulating its release.