Postnatal development of the dopaminergic neurons in the rat mesencephalon

The two mesencephalic dopaminergic systems in the developing rat brain were investigated immunohistochemically by dopamine and tyrosine hydroxylase and the results were quantitatively analyzed with a computer. The number of the dopaminergic neurons in the substantia nigra and the ventral tegmentum area did not change significantly during the postnatal development. Dopaminergic terminals in the lateral septum peaked at postnatal days (PD) 30, when the cell size in middle third of the ventral tegmentum area which was suggested as an origin of this projection system, increased largely. Patchy structures in the striatum were shown most distinctly at PD 7 and disappeared at PD 35 using dopamine antibody, but there were no changes in the cell size of the substantia nigra from PD 14 to 75. Dopaminergic neurons, in general, do not show a transient change in ontogeny.