Dopaminergic neuronal development in the embryonic mesencephalon of mouse

This study presents neuronal migration pattern of dopamine (DA) neurons generated in separate regions occupying the ventral mesencephalic territory. A single pulse 5-bromodeoxyuridine (BrdU) was administered at embryonic day (E)10-E15. Distribution of tyrosine hydroxylase (TH) positive cells was determined at E13-postnatal day 0 (P0) by immunohistochemistry. BrdU positive cells labeled at E10 were spread out uniformly in the mesencephalon from E13 to E15, migrating through dorsal and ventral routes at E17 and P0. TH expression labeled at E10 was observed at E13 in the ventromedial region and clearly formed in the ventral tegmental area (VTA) at E15. At E17, TH expression in the substantia nigra (SN) was observed in the ventrolateral region, spreading more outward of the mesencephalon at P0. Generation of TH-positive cells labeled at E13 was also observed in VTA and SN of the mesencephalon at E17 and P0. The expression of these cells labeled after E15 was markedly decreased. These results demonstrated that an almost complete primary structure of DA neuron was formed at the early embryonic stage in the ventral mesencephalon, showing the most active neuronal migration was occurred at E13-E17.