ANTIESTROGEN INHIBITS MYELINATION IN BRAINS OF JUVENILE ZEBRA FINCHES

THE effects of the antioestrogen Keoxifene on the ontogenetic process of myelination, on the differentiation of neurones of telencephalic so ng motor centres, on cerebellar structures and on behaviour were studi ed in male Zebra finches. Brain differentiation was studied by using c omputer aided analysis of silver impregnated brain sections and by mea suring soma sizes of neurones after Nissl staining. An antioestrogen i nduced inhibition of myelination could be detected in the song motor c entre robust nucleus of the archistriatum (RA) and in the cerebellum, whereas the region magnocellular nucleus of the anterior neostriatum ( MAN) showed no difference between treated birds and controls.