Expression of two glutamate transporters, GLAST and EAAT4, in the human cerebellum: their correlation in development and neonatal hypoxic-ischemic damage.

Normal development and hypoxic-ischemic changes of glutamate-aspartate transporters (GLAST) and excitatory amino acid transporter type 4 (EAAT4) were demonstrated in the human cerebellum. GLAST-immunoreactive Bergmann's glia and EAAT4-positive Purkinje cells showed a specific distribution and localization, and developed with age in the molecular and Purkinje cell layers. The dendrites and cell bodies of Purkinje cells, which showed EAAT4 immunoreactivity, were ensheathed by GLAST processes. In neonatal hypoxic-ischemic encephalopathy (HIE), GLAST immunoreactivity decreased in the molecular layer and increased in the inner granule cell layer at an early stage, and markedly increased in the Purkinje and inner granule cell layers at a late stage. EAAT4 immunoreactivity decreased with post-ischemic changes of Purkinje cells. GLAST reactivity changed more rapidly than EAAT4 in cases of HIE. These changes of GLAST and EAAT4 may be closely related to the vulnerability of Purkinje cells in hypoxia-ischemia. The glutamate transporter of Bergmann glia may play a more important role in the regulation of the extracellular glutamate concentration in hypoxia and/or ischemia.