Chemical neuroanatomy of the substantia nigra in the ovine brain.

The substantia nigra is an integral component of the basal ganglia circuitry for limbic and motor functions. Dysfunction and degeneration of the basal ganglia are fundamental aspects of neurodegenerative diseases such as Parkinson's disease and Huntington's disease. With the increasing use of sheep to model neurological diseases, it is crucial to understand the anatomy and neurochemistry of these key basal ganglia nuclei in the normal sheep brain and how they compare to the human brain.