Key points are not available for this paper at this time.
We have used postnatal rat cerebellar astrocyte-enriched cultures to study the excitatory amino acid receptors present on these cells. In the cultures used, type-2 astrocytes (recognized by the monoclonal antibodies A2B5 and LB1) selectively took up gamma-3Haminobutyric acid (3HGABA) and released it when incubated in the presence of micromolar concentrations of kainic and quisqualic acids. The releasing effect of kainic acid was concentration dependent in the range of 5-100 microM. Quisqualate was more effective than kainate in the lower concentration range but less effective at concentrations at which its releasing activity was maximal (approximately 50 microM). N-Methyl-D-aspartic acid and dihydrokainate (100 microM) did not stimulate 3HGABA release from cultured astrocytes. L-Glutamic acid (20-100 microM) stimulated 3HGABA release as effectively as kainate. The stimulatory effects of kainate and quisqualate on 3HGABA release were completely Na+ dependent; that of kainate was also partially Ca2+ dependent. Kynurenic acid (50-200 microM) selectively antagonized the releasing effects of kainic acid and also that of L-glutamate; quisqualate was unaffected. Quisqualic acid inhibited the releasing effects of kainic acid when both agonists were used at equimolar concentrations (50 microM). D-3Haspartate was taken up by both type-1 and type-2 astrocytes, but only type-2 astrocytes released it in the presence of kainic acid. Excitatory amino acid receptors with a pharmacology similar to that of the receptors present in type-2 astrocytes were also expressed by the immature, bipotential progenitors of type-2 astrocytes and oligodendrocytes.
Gallo et al. (Sun,) studied this question.