Parkinson's disease is the deficit of a __________ neurotransmitter.

• A. Dopamine
• B. Acetylcholine
• C. GABA
• D. Glutamate

Answer: (A)

The main idea is that Parkinson's disease stems from a loss of dopamine in the brain’s movement circuits. When dopaminergic neurons in the substantia nigra degenerate, dopamine in the nigrostriatal pathway drops, shifting the balance toward acetylcholine and impairing the smooth initiation and control of movement. That’s why motor symptoms like tremor at rest, bradykinesia, rigidity, and slowed movement appear.

Acetylcholine isn’t the primary deficit; rather, its activity becomes relatively stronger when dopamine falls, contributing to the symptoms. GABA and glutamate are involved in the broader basal ganglia networks, but the core deficit in Parkinson’s is the reduced dopamine availability. This is why treatments aim to boost dopamine levels or mimic its action (and sometimes reduce acetylcholine’s relative influence) to improve motor control.