Figure 2.

Intrinsic properties of dopaminergic (DA) neurons in the substantia nigra (SN). The nigrostriatal DA neurons are autonomous pacemakers, and their tonic spontaneous activity is important for the sustained release of dopamine in target structures, such as the striatum. In addition, DA neurons in the SN have thin, unmyelinated axons with an extraordinary large axonal arbor and a very high number of synaptic terminals. The size and complexity of DA neurons in the SN impose a high metabolic burden to produce ATP, which is required for transporting cellular components to appropriate locations, maintaining resting membrane potential, generating and propagating action potential, and regulating synaptic transmission. Metabolically active DA neurons in the SN are susceptible to mitochondrial dysfunction, which is a prominent feature of both aging and PD. Created with BioRender.com.