In kitten area 17 vimentin-like immunoreactivity is expressed in radial glial fibres up to one month postnatally, i.e. the time for which neuronal migration continues. During this time fibre density gradually decreases. A subpopulation of these fibres also contains S-100 protein and glial fibrillary acidic protein. However, these latter antigens disappear earlier than vimentin. In addition, vimentin immunoreactivity can be observed in astroglial cells of the white matter between the second and fifth postnatal week. Many of these cells resemble mature astrocytes but partially they have an intermediate morphology suggesting the possibility that they originated from radial glia. Such displaced radial glial cells' are also positive for S-100 protein both in the cortex and white matter. Thus it is conceivable that at least part of the astrocytes of mature cat visual cortex originate from vimentin- or S-100-immunoreactive radial glia.
