The substantia nigra pars compacta of the Göttingen minipig: an anatomical and stereological study.

Parkinson disease (PD) is a neurodegenerative disorder resulting from progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNc). Despite advances in medical and surgical therapies, many PD patients experience progression of their symptoms and medical side effects over time. To explore new treatments, new animal models mimicking the progressive PD nature are needed. The pig is well suited for this purpose with its large gyrated brain, sensitive to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The objective of this study was to provide the anatomical foundation for such a model, describing in detail the SNc in normal Göttingen minipigs and estimating the volume and total number of tyrosine hydroxylase (TH)-positive neurons. The brain stems of 6 Göttingen minipigs were paraffin embedded and serially cut before Nissl staining and immunohistochemical visualization of TH. The volume of the SNc and the total number of TH-positive neurons were estimated by design-based stereology. The substantia nigra was located at the dorsal rim of the crus cerebri extending throughout the mesencephalon. A dorsal pars compacta and a ventral pars reticulata were demonstrated. The SNc merged with the ventral tegmental area medially and the retro-rubral field dorsocaudolaterally. The total number of TH-positive neurons in the SNc unilaterally was estimated to 80,700 [74,100;87,300], and the volume estimate was 26.4 mm(3) [25.0;27.8]. We conclude that the anatomy of the SNc in the Göttingen minipig corresponds well with that of higher primates, and is well suited for further studies aimed at optimizing this non-primate large animal model for PD.