ZEBRIN-II IMMUNOREACTIVITY IN THE RAT AND IN THE WEAKLY ELECTRIC TELEOST EIGENMANNIA (GYMNOTIFORMES) REVEALS 3 MODES OF PURKINJE-CELL DEVELOPMENT

Monoclonal antibody (mab) anti-zebrin II recognizes a single 36-kD polypeptide in Purkinje cells in the rat and fish cerebellum. In the adult rat, zebrin II+ Purkinje cells form, in each hemicerebellum, seven parasagittal bands interposed by zebrin II- bands. We show that, in rats, immunoreactivity first appears caudally at postnatal day 5 and spreads; all Purkinje cells are labelled by postnatal day 12. Subsequently, immunoreactivity is selectively lost so that by day 18 the adult pattern of zebrin II+/- immunoreactive bands is created. This pattern indicates two types of Purkinje cells according to developmental trajectory, zebrin II-/+ and zebrin II-/+/-. In the adult gymnotiform teleost Eigenmannia, Purkinje cells in the corpus cerebelli (CCb), lateral valvula cerebelli (VCbl), and eminentia granularis anterior (EGa) are zebrin II+. Purkinje cells in the eminentia granularis posterior (EGp) and medialis (EGm) and the medial valvula cerebelli (VCbm) are zebrin II-. Zebrin II antigenicity is first present at 6 days postspawning (P6) in the EGa and at P8 in the CCb. In the valvula, labelling does not appear until P29. Immunoreactivity in the CCb, VCbl, and the EGa persists in the adult whereas in the VCbm Purkinje cells become zebrin II- before reaching adulthood. These developmental histories (zebrin II-/+ and zebrin II-/+/-) correspond to the patterns of Purkinje cell development in mammals. Additionally, Eigenmannia has a third class of Purkinje cells, in the EGp and EGm, that never express zebrin II immunoreactivity, indicating that zebrin II expression is not an obligatory feature of Purkinje cell development in all vertebrates.