Stereologic analysis of cell number and size during postnatal development in the rat substantia nigra.

Parkinson's disease is characterized by age-related atrophy and loss of dopaminergic neurons within the compact portion of the substantia nigra (SNpc) projecting to neostriatum. Despite numerous studies using rodent models to examine mechanisms underlying this disorder, the fundamental question of whether development- or age-related changes occur in the rodent SNpc remains unanswered. The present study used a three-level, optical fractionator approach to estimate the number and size of SNpc neurons immunoreactive for tyrosine hydroxylase (TH) in eight young (2-month) and eight older (7-month) Sprague-Dawley rats.