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Figure 4

Nature Neuroscience  7, 1034 - 1039 (2004)
Published online: 27 September 2004; | doi:10.1038/nn1325

Sexual differentiation of the vertebrate nervous system

John A Morris, Cynthia L Jordan & S Marc Breedlove
Fig 4 full size
Figure 4. In newly hatched zebra finches, axons from HVC reach the vicinity of their target in RA, but do not actually enter RA in significant numbers unless estrogen receptors are stimulated.
For example, treating young females with estrogen promotes axonal ingrowth into RA and a large, masculine RA in adulthood. But interfering with gonadally produced estrogen in males does not prevent masculine development, so it has been hypothesized that the genetically male zebra finch brain may produce its own estrogen to induce HVC ingrowth and masculine development. Explants of zebra finch brain confirm this idea, as slices from males release more estrogen into the medium than do slices from females39.

Debbie Maizels

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