High number of striatal dopaminergic neurons during early postnatal development: correlation analysis with dopaminergic fibers

Dopamine (DA) axons in the developing striatum cluster in discrete areas called ‘‘DA islands’’. During the third postnatal week, most DA islands are no-longer detectable and the DA innervation becomes uniform. In this study we explored the relationship between the pattern of DA innervation and the number of striatal tyrosine hydroxylase positive (TH?) cells during early postnatal development. By using dedicated stereology we found that the newborn striatum contains striatal TH? cells, which cluster around newly sprouted DA axons. The number of these cells decreases when DA axons develop a full pattern of striatal innervation. This condition suggests a causal relationship between the amount of striatal DA innervation and the presence of striatal DA neurons. A better knowledge of the mechanisms regulating the ontogenesis of the nigrostriatal DA system may pave the way to strategies of neurorescue of the DA system.