NEUROGENESIS OF CATECHOLAMINE NEURONS IN THE MOUSE BRAIN STEM

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The time course of production of catecholamine neurons in the mouse brain stem was examined by [³H]thymidine autoradiography and peroxidase-antiperoxidase (PAP)-immunocytochemistry applied simultaneously to the same tissue section. To identify catecholamine neurons, an antiserum for tyrosine hydroxylase (TH) was used. The period of neurogenesis of TH-immunoreactive neurons was embryonic day 9-11 (E9-E11) in the lateroventral reticular formation of the medulla oblongata (A1), E9-E12 in the nucleus tractus solitarii complex (A2), E9-E11 in the locus coeruleus (A6), E10-E13 in the substantia nigra (A9) and the ventral tegmental area (A10), and E11-E15 in the hypothalamic arcuate nucleus (A12). The peak of neurogenesis was seen in E10 for Al and A6, in E11 for A2, A9 and A10, and in E13-E14 for A12. The results indicate that noradrenergic neurons (A1, A2, A6) begin to be produced earlier than dopaminergic neurons (A9, A10, A12). Among the noradrenergic neurons, A2 cells differentiated later and took a longer period than A1 or A6 cells. Most of the hypothalamic A12 cells were produced after the midbrain dopaminergic cells (A9, A10) had differentiated. The data indicate that the neurogenesis of catecholamine neurons occurs in varying time sequence according to their location in brain and begins several days earlier than the phenotypic expression of catecholamines.