The substantia nigra (“black substance”) gets its name from the melanin-pigmented dopaminergic neurons of the pars compacta (SNc). SNc projects dopamine to the striatum, modulating the direct/indirect pathways. The GABAergic pars reticulata (SNr) functions as a primary output nucleus of the basal ganglia, projecting to the thalamus.
Loss of SNc dopaminergic neurons is the defining pathology of Parkinson’s disease.