MESENCEPHALIC DOPAMINERGIC CELLS EXHIBIT INCREASED DENSITY OF NEURAL CELL-ADHESION MOLECULE AND POLYSIALIC ACID DURING DEVELOPMENT

In the developing mesencephalon of the rat, the dopaminergic neurons are generated in the ventricular zone of the basal plate between E11 and E15 and then migrate along radial glia to the ventral surface of the developing mesencephalon, To study the factors that control migration and maturation of the dopaminergic neurons, we immunolabeled embryo and pups, ages E12-P21, for neural cell adhesion molecule (NCAM), polysialic acid (PSA) - a polysaccharide found in high amounts on NCAM during development, tyrosine hydroxylase (TH) - a marker of mesencephalic dopaminergic cells, and vimentin - the major cytoskeletal protein in radial glia in the rat. At E13, we noted that cells throughout the mesencephalon contained NCAM-immunoreactive (NCAM-IR) material but that cells along the ventral surface of the mesencephalon contained an increased amount of NCAM-IR material and PSA-immunoreactive (PSA-IR) material. At this age, we first noted a small number of TH-immunoreactive (TH-IR) cells adjacent to the marginal zone of the ventral surface of the mesencephalon. Many of the TH-IR cells contained an increased density of NCAM-IR material. At age E14, the pattern of increased density of NCAM-IR material on cells along the ventral surface of the mesencephalon persisted and a conspicuous amount of PSA-IR material was also noted on cells in this region. TH-IR cells were more numerous, and a striking number of the TH-IR cells also contained an increased amount of NCAM-IR material and PSA-IR material. With increasing age the distribution of NCAM-IR material and PSA-IR material in the mesencephalon became more uniform. Our work suggests that NCAM may be involved in control of migration and synthesis of TH in the dopaminergic cells of the developing mesencephalon.