Histogenesis of dopamine-containing neurons in the rat retina

The point during development when a neuron in the central nervous system ceases to divide is a crucial early step in differentiation which may be a prerequisite for phenotypic expression. In this double-label study, which combines [3H]thymidine autoradiography with histochemical detection of endogenous dopamine, we examined the histogenesis of dopamine-containing cells (DA-cells) in the amacrine layer of the rat retina. We found that most DA-cells present in the adult rat retina stop dividing between embryonic days 16 and 20. These results show that most cells destined to become dopaminergic neurons are generated during a discrete interval within the extended period of amacrine-cell production, and that these cells are produced in the embryonic retina.