Cerebellar glutamate metabolizing enzymes in spinocerebellar ataxia type I.

We measured the levels of three glutamate metabolizing enzymes, namely, glutamate dehydrogenase (GDH), aspartate aminotransferase (AAT), and glutamine synthetase (GS) in cerebellar and occipital cortices of nine patients with dominantly-inherited olivopontocerebellar atrophy (OPCA; spinocerebellar ataxia type I). As compared with the controls, mean GDH activities in cerebellar cortex of the OPCA patients were normal whereas levels of AAT (-17%) and the glial enzyme GS (-27%) were significantly reduced. No statistically significant changes were observed in occipital cortex, a morphologically unaffected brain area. We suggest that the decreased GS levels could reflect impaired capacity of astrocytes to metabolize glutamate which might contribute to the degenerative processes in OPCA cerebellum.