The effects of postnatal hyper- and hypothyroidism on the development of D-amino acid oxidase in rat cerebellum and brain stem.

Treatment of rats with propylthiouracil for the first 30 days of postnatal life drastically retards the ontogenesis of D-amino acid oxidase in the brain stem and cerebellum. There is a marked terminal deficit of D-AAO in both the brain stem (--64%) and cerebellum (--67%) at 94 days (adults) despite the near euthyroid status at this age. If initiated early enough, thyroxine replacement therapy reverses the effects of PTU on the development of D-AAO. Hyperthyroidism significantly accelerates the development of D-AAO in both brain stem and cerebellum. Nonetheless, animals treated with thyroxine the first month of life display a net deficit of cerebellar D-AAO content in adulthood. The results are discussed in terms of the localization of D-AAO in cell types especially sensitive to thyroid hormone: (1) a cell type which is among the last to derive from the external germinal zone in the developing cerebellum, and which in the adult is located adjacent to the Purkinje cell soma; and (2) mossy fiber neurons and cerebellar glomeruli.