Fig. 2.

Substantia nigra degeneration in PD and dementia with Lewy bodies. The core pathology of PD affects the DA-producing neurons of the substantia nigra (SN). DA is produced by SN neurons and transported along the axons of these neurons to the striatum. The triad of rigidity, bradykinesia and tremor at rest, correlates with degeneration of the dopaminergic nigrostriatal pathway and DA depletion in the striatum. In advanced PD, loss of these neurons results in depigmentation of the SN (A) and in loss of the DA synthesising enzyme tyrosine-hydroxylase (TH) (B-C). PD is a synucleinopathy. Fibrils made of insoluble polymers of α-synuclein are deposited in the neuronal body, forming round lamellated eosinophilic cytoplasmic inclusions, the Lewy bodies (D). α-synuclein is also deposited in neuronal processes