Journal of Neuroscience, Vol 7, 1969-1978, Copyright © 1987 by Society for Neuroscience
Pattern formation in the striatum: developmental changes in the distribution of striatonigral neurons
G Fishell and D van der Kooy
The striatum of the mammalian forebrain can be divided into 2 compartments,
the patches and the matrix. We have investigated embryonic events involved
in the formation of these compartments in rats. Early in development,
dopamine fibers from the substantia nigra selectively innervate the
patches. In the perinatal striatum, we observed a close match between the
distributions of striatal cell bodies with axonal projections to the
substantia nigra and patches of afferent dopamine fibers. Striatal cells
projecting to the nigra are first seen in the ventrolateral striatum at
embryonic day (E) 17. Striatonigral cell bodies are distributed
homogeneously through the striatum from E18 to 19. At E20 and until
postnatal day 4, these cell bodies are organized into discrete patches.
After this time, striatonigral cell bodies assume the dense and homogeneous
distribution characteristic of the adult striatum. A retrograde tracer
injection in the nigra at E18 (during the early period of homogeneous
striatonigral distribution) produces a patchy striatonigral distribution if
the embryo is not sacrificed until E21. The number of retrogradely labeled
striatonigral cell bodies in a midstriatal section, at times immediately
before and after the early homogeneous to patchy changeover did not differ
significantly. We suggest that the neurons of the patch compartment of the
striatum are born first and project to the substantia nigra first. The
patch neurons only become restricted to "patchy" areas as the later-born
matrix neurons migrate out into the striatum.
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