Which neurotransmitter is primarily lacking in the brain of patients with Parkinson's disease?

In patients with Parkinson's disease, the primary neurotransmitter that is deficient is dopamine. This is due to the degeneration of dopaminergic neurons in the substantia nigra, a crucial region in the brain that is involved in the regulation of movement. The loss of dopamine disrupts the balance of neurotransmitters in the brain, leading to the hallmark motor symptoms of Parkinson's disease, such as tremors, rigidity, and bradykinesia, as well as non-motor symptoms.

Dopamine plays a vital role in the basal ganglia pathways that facilitate smooth and controlled movements. When dopamine levels decrease, the inhibitory and excitatory signals within these pathways become unbalanced, contributing significantly to the movement difficulties experienced by patients. Thus, the reduction of dopamine is central to the pathophysiology of the disease, making it the primary neurotransmitter of concern in this context.