The present immunoperoxidase cytochemical study describes the distribution of glial intermediate filament
molecular markers, glial fibrillary acidic protein (GFAP) and vimentin, in the brain and spinal cord of the
adult lizard, Podarcis sicula. GFAP immunoreactivity is abundant and the positive structures are mainly
represented by fibres of different lengths which are arranged in a rather regular radial pattern throughout
the CNS. They emerge from generally immunopositive radial ependymoglia and are directed from the
ventricular wall towards the meningeal surface. The glial fibres give origin to endfeet which are apposed to
the blood vessel walls and subpial surface where they form the continous perivascular and subpial glia
envelopes, respectively. In the optic tectum and spinal cord, star-shaped astrocytes coexist with radial glia.
In the spinal cord, cell bodies of immunopositive radial glia are displaced from the ependyma. While
vimentin immunoreactive elements are almost completely absent in the brain except for a few diencephalic
radial fibres, the spinal cord ependyma exhibits a clearly vimentin positivity and no GFAP staining. In the
Podarcis CNS the immunocytochemical response of the astroglial intermediate filaments appears typical of
mature astroglia cell lineage since it fundamentally expresses GFAP immunoreactivity. Moreover, this
immunocytochemical study shows that the Podarcis fibre pattern with predominant radial glial cells is
morphologically more immature than in avians and mammalians, a condition suggesting that reptiles
represent a fundamental step in the phylogenetic evolution of vertebrate astroglial cells.