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pars compacta

Structure: - the pars compacta of the substantia nigra is a dorsal stratum of 450,000 closely spaced pigmented, melanin-containing dopaminergic neurons. - these darkly pigmented dopaminergic neurons contain 80% of dopamine in the central nervous system. Efferents: - the dopaminergic neurons project inhibitory fibers to the striatum (caudate & putamen) - other non dopaminergic neurons project to the rostral part of the ventral nucleus of the thalamus Afferents: - the nigrostriatal system is reciprocated by a massive striatonigral fiber system with multiple neuro-transmitters, but chiefly GABA - the substantia nigra receives smaller afferent projections from the subthalamic nucleus, the lateral segment of the globus pallidus, the dorsal nucleus of the raphe, & the pedunculopontine nucleus of the midbrain. Pathology: - the pars compacta appears depigmented with loss of neurons in brains from victims of Parkinson's disease

General

CNS nucleus

References

  1. Stedman's Medical Dictionary 26th ed, Williams & Wilkins, Baltimore, 1995
  2. Lang & Lazano NEJM 339:1044-53, 1998

Component-of

substantia nigra (nucleus niger, Soemmerring's ganglion)