Prenatal development of the biogenic amine systems of the mouse brain

The development of catecholamine- and serotonin-containing neural structures in the brain of the fetal mouse was studied utilizing the Falck-Hillarp technique of histofluorescence. The substantia nigra, ventral tegmental region, and striatum show progressive developmental changes following the initial appearance of fluorescence on gestational day 13. Fluorescent nigrostriatal axons are present on days 13 through 17. The locus ceruleus becomes visible on day 14. Axon terminals in the hypothalamus first are seen on day 19. Cells of the mesencephalic and pontine raphe systems become brightly fluorescent on day 13. Medullary raphe cells appear the following day. No serotonergic axon terminals were visualized in the fetus.