Black core compact part

Substantia nigra pars compacta


SNc is located on hay. and we. side of the midbrain and forms the deep/dorsal layer of the substantia nigra.
SNc is counted among the basal ganglia.

SNc consists of a thin layer of tightly packed dopamine-producing neuronal bodies (A9), which contain black-brown color grains: neuromelanin (oxidized and polymerized dopamine). The dopamine is transported from the cell bodies out into the axon, stored in varicosities and boutons and released when the nerve cell discharges itself; sends out action potentials.

The main signal output/efference from SNc ends in the striatum. Here, dopamine causes "The direct pathway through the basal ganglia" to be strengthened and at the same time "The indirect pathway through the basal ganglia" to be weakened. This facilitates the flow of impulses from/through the thalamus to the cortex and promotes motor skills.

The inflow of nerve signals - afference - to SNc is primarily based on other members of the group "The basal ganglia" and is mostly of a slowing/inhibitory nature (GABA). Propulsive/excitatory signals emanate from the subthalamic and pedunculopontina nuclei (glutamate and acetylcholine).

The SNc neurons are spontaneously active with the frequency 1-2 discharges/sec; i.e. are active in themselves without external influences. Under external influence, the spontaneous rhythm decreases or, as in reward situations, turns into short impulse bursts.

Impaired production of dopamine in SNc gives rise to Parkinson's disease.

Carlsson, A. (1988) Speculations on the control of mental and motor functions by dopamine-modulated cortico-striato-thalamo-cortical feedback loops. Mt Sinai J Med. Jan; 55(1):6-10.
Carlsson, A. (1993) Thirty years of dopamine research. Adv Neurol.; 60:1-10.
Lee CR, Tepper JM (2009) Basal ganglia control of substantia nigra dopaminergic neurons. J Neural Transm Suppl. (73):71-90.