Abstract

We consider the evidence that RA†, the vitamin A metabolite, is involved in three fundamental aspects of the development of the CNS: (1) the stimulation of axon outgrowth in particular neuronal sub‐types; (2) the migration of the neural crest; and (3) the specification of rostrocaudal position in the developing CNS (forebrain, midbrain, hindbrain, spinal cord). The evidence we discuss involves RA‐induction of neurites in cell cultures and explants of neural tissue; the teratological effects of RA on the embryo's nervous system; the observation that RA can be detected endogenously in the spinal cord; and the fact that the receptors and binding proteins for RA are expressed in precise domains and neuronal cell types within the nervous system.