Protein and RNA synthesis in kainic acid-injected striata

Increase in nucleoside diphosphatase in rat brain striatum lesioned with kainic acid

The activity of ammoniagenesis from guanine nucleotides was found to increase significantly in rat brain after infusion of kainic acid into the striatum. Among the enzymes involved in degrading guanine nucleotides, nucleoside diphosphatase was markedly increased in the lesioned striatum. The enzyme activity began to increase 2 days after the infusion, and reached the maximum on the 13th day, the level being 4 times as high as that of the intact contralateral region. The increased activity was due to Type L enzyme, judging from its substrate specificity. Puromycin and cycloheximide inhibited this increase, indicating that the increased activity resulted from an increase in the net synthesis of the enzyme. These findings suggest that Type L NDPase might play some important roles in gliosis after neuronal lesion.

Morphologic evidence of a primary response of gila to kainic acid administration into the rat neostriatum; studied in vivo and in vitro

Glial changes that follow kainic acid administration were studied in the rat neostriatum at many different time intervals after the lesion, both in the animal model of Huntington's chorea and in an organotypic culture of striatum. The glial reaction showed striking similarities between in vivo and in vitro conditions and resulted in extensive production and accumulation of gliofilaments leading to transformation of the protoplasmic type of astroglia into the fibrous type. The earliest ultrastructural study in vivo revealed severe swelling of the astrocytic cytoplasm and additional morphologic changes of cytoplasmic organelles, i.e., enlargement of mitochondria, dilation of rough endoplasmic reticulum, and presence of numerous vacuoles. The glial pathology progressed parallel to neuronal degeneration. The same reaction was observed in culture both in the explanted tissue in which neurons remained intact and in the distant outgrowth zone containing a pure population of glial cells. This study proved that kainic acid might act directly on astroglia cells and that glial changes were independent of neuronal damage. Because kainic acid is a structural analog of glutamate, the presented results may be interpreted to reflect changes in the metabolism of this amino acid occurring in astroglia independently of neuronal changes. This interpretation is consistent with the existence of two independent metabolic compartments of glutamate.

Glycolysis in rat neostriatal slices following kainic acid injections

In in vitro incubations, kainic acid-lesioned neostriatal slices from rat brain showed decreases in oxygen consumption (50%) and in the conversion of both [1-14C]glucose (43%) and [6-14C]glucose (69%) to 14CO2 as compared to controls. The elevation in the C1/C6 14CO2 ratio suggested the pentose phosphate pathway was less affected than the Embden-Meyerhof path in kainic acid-injected gliotic tissue. Increasing the potassium concentration from 6 to 50 mM caused increases in oxygen consumption and glucose utilization in both control and kainic acid-lesioned neostriatal slices; this is consistent with, but not conclusive of, a potassium-stimulating effect on glial as well as neuronal metabolism.

Metabolic alterations in an animal model of Huntington's disease using the 14C-deoxyglucose method

Various brain regions showing altered glucose uptake in an animal model of Huntington's disease (HD) were identified by the 14C-2-deoxyglucose (DG) autoradiographic technique. Rats with kainic acid (KA) lesions of the neostriatum were used as an animal model of HD. KA-injected animals showed reduced utilization of DG in the injected neostriatum as well as in the ipsilateral rostral sulcal cortex, dentate fascia of hippocampus, ventromedial nucleus of the thalamus and cortico-bulbar tract. By contrast, enhanced uptake was found in the ipsilateral globus pallidus, entopeduncular nucleus, the area lateral to the lateral hypothalamus, the lateral habenular nucleus and pars reticulata of the substantia nigra. The results provide interesting in vivo metabolic and functional information on brain circuits involved in motor performance.