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

Propylthiouracil treatment reduces long-term potentiation in area CA1 of neonatal rat hippocampus

Rat pups were made hypothyroid by exposure to propylthiouracil in drinking water beginning at 1 week of age, and the degree of long-term potentiation (LTP) in hippocampal area CA1 determined from brain slices of animals ranging in age from 2 to 6 weeks. Serum T3 levels were less than 20% of that of age matched controls after 3 weeks of treatment, and remained at that level. Relative to the age-matched controls, LTP was reduced significantly after 2 weeks of treatment. These observations are consistent with the conclusion that LTP magnitude is a reflection of cognitive function, which is known to be depressed in hypothyroid conditions in both animals and man.

Antioxidant enzymes in the brain of zitter rats: abnormal metabolism of oxygen species and its relevance to pathogenic changes in the brain of zitter rats with genetic spongiform encephalopathy

Zitter rats develop a genetic spongiform encephalopathy characterized by edematous changes in their brains. In order to elucidate the involvement of reactive oxygen species in this process we examined age-related alterations of the activities of the enzymes which metabolize reactive oxygen species. Activities of superoxide dismutase (SOD), D-amino acid oxidase (D-AAO), glutathione peroxidase (GSH-Px) and catalase in the brain and the liver of zitter rats are compared with those of control SD/J rats. In the brain of adult zitter rats which show degenerative changes, significantly enhanced activities of SOD and D-AAO were obtained, whereas activity of catalase was lower than that of the SD/J rats. Prominent abnormalities in catalase and D-AAO but not in SOD activity were demonstrated before or at the same time as the appearance of the morphological vacuolation in the brain of suckling zitter rats. There was no difference in GSH-Px activity between the brains from zitter and SD/J rats. These results suggest that the alteration of hydrogen peroxide (H2O2)-metabolism in microperoxisomes may play an important role in the initiation of degenerative changes in the brain of zitter rats. Enhanced SOD activity observed in the brain of adult zitter rats may be a compensatory response to the high superoxide anion produced in the course of cell damage caused by the H2O2 stagnation. Also, more SOD might produce more H2O2.

Localization of D-amino acid oxidase in Bergmann glial cells and astrocytes of rat cerebellum

The localization of D-amino acid oxidase in rat cerebellum was systematically studied in serial fixed sections at the levels of both light and electron microscopy using a coupled peroxidation method based on the intensifying effect of nickel ions. Deposits were only seen in astrocytes and Bergmann glial cells, and not in neuronal components, endothelial cells or ependymal cells. In the molecular layer, heavy deposits were present in the profiles of Bergmann glial processes around the complexes of synapses where the parallel fiber varicosities form synapses with the thorns emerging from the spiny branchlets of Purkinje cell dendrites. In the Purkinje cell layer, the oxidase-containing processes of Bergmann glial cells enveloped basket cell axons, their terminals, the terminals of the recurrent collaterals of Purkinje cell axons and Purkinje cell bodies. In the granular layer, the cerebellar glomeruli were enveloped by the heavily stained processes of astrocytes. Based on this characteristic localization of the oxidase, we discussed the physiological role of the oxidase in connection with the function of glial cells.