Postnatal neurogenesis in the nucleus sphericus of the lizard, Podarcis hispanica

Autoradiography was used to demonstrate the genesis and migration of cells in the nucleus sphericus of perinatal, juvenile and adult lizards, Podarcis hispanica (Sauria, Lacertidae). Following intraperitoneal injections of [3H]thymidine (5 microCi/g b. w.) and survival times of 1, 7, 18 and 28 days, labelled cells were found in the ependyma, marginal layer and mural layer of the nucleus sphericus in specimens of all ages. After short survival times, most labelled cells were located in the ependymal layer. Longer survival times resulted in labelling of cells mainly in the mural layer. At intermediate survival times, a substantial number of labelled cells was also found in the marginal layer. The time course of labelling suggests that neuronal proliferation takes place in the ependyma surrounding the ventricle. Subsequently, the newly formed neurons migrate centripetally and are recruited into the mural layer.