Dopaminergic neurons are one of the major neuronal components in the brain. Mesencephalon dopamine (DA) neurogenesis takes place in the ventricular zone of the floor plate, when DA progenitors divide to generate postmitotic cells. These cells migrate through the intermediate zone while they differentiate and become DA neurons on reaching the mantle zone. However, neurogenesis and neuronal migration on dopaminergic neurons remain largely unexplored in the mesencephalon development. This study presents neurogenesis and neuronal migration patterns of dopaminergic neurons during mesencephalic development of the mouse. Neurons from embryonic day (E) 10–14 were labelled by a single injection of 5-bromodeoxyuridine and immunohistochemistry was performed. The neurogenesis occurred mainly at the E10 and E11, which was uniformly distributed in the mesencephalic region, but neurons after E13 were observed only in the dorsal mesencephalon. At the postnatal day 0 (P0), E10 generated neurons were spread out uniformly in the whole mesencephalon whereas E11-originated neurons were clearly depleted in the red nucleus region. DA neurons mainly originated in the ventromedial mesencephalon at the early embryonic stage especially E10 to E11. DA neurons after E12 were only observed in the ventral mesencephalon. At E17, E10 labelled neurons were only observed in the substantia nigra (SN) region. Our study demonstrated that major neurogenesis occurred at E10 and E11. However, neuronal migration continued until neonatal period during mesencephalic development.

Introduction
 Materials and Methods
  Animals
  5-Bromodeoxyuridine labeling and immunohistochemistry
 Results
  Neurogenesis and neuronal migration in the mesencephalon
  Dopaminergic neuronal development in the mesencephalon
 Discussion
 References

• Mun-ki Kim(Research Institute of Life Science & Department of Veterinary Medicine, Gyeongsang National University)
• Si-Joon Lee(Research Institute of Life Science & Department of Veterinary Medicine, Gyeongsang National University)
• Anju Vasudevan(Angiogenesis and Brain Development Laboratory, McLean Hospital/Harvard Medical School)
• Chungkil Won(Research Institute of Life Science & Department of Veterinary Medicine, Gyeongsang National University) Corresponding author