- The primary neurotransmitter pathway affected in the pathophysiology of Parkinson's disease is the dopaminergic pathway.
- Parkinson's disease is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta, a region of the midbrain.
- This leads to a significant reduction in dopamine levels within the striatum, which is critical for the regulation of motor control.
- The decrease in dopamine disrupts the balance between excitatory and inhibitory pathways in the basal ganglia, resulting in the hallmark motor symptoms of Parkinson's disease, such as bradykinesia, rigidity, resting tremor, and postural instability.

- While cholinergic, GABAergic, and serotonergic systems are also involved in brain function and may be altered in Parkinson's disease, they are not the primary neurotransmitter systems implicated in its core motor symptoms.
- Therapeutic strategies for Parkinson's often focus on restoring dopaminergic function, either through dopamine replacement (e.g., levodopa) or dopamine agonists.

Reference: Adams and Victor's Principles of Neurology, 11th Edition, Chapter 22: Parkinson's Disease and Movement Disorders