Inhibitory properties coexist with plasticity in the song system of the canary

The expression of neuronal growth regulating factors (Ni 35/250, GAP-43) were studied immunohistochemically in the plastic telencephalic song system and in the cerebellum of the canary. In the myelinated song nuclei (HVc and RA) growth promoting and inhibiting molecules could be detected, whereas in the white matter tracts of the cerebellum only the neurite growth inhibitor could be detected. The morphodynamic effects of these molecules were assessed by in vitro assays on cryosections. Neurites were formed by 20-30% of the E7 chick cortical neuroblasts cultured in myelinated areas of the vocal control system, neurite outgrowth from the white matter of the cerebellum was completely inhibited.