Phosphorylation of glial fibrillary acidic protein is stimulated by glutamate via NMDA receptors in cortical microslices and in mixed neuronal/glial cell cultures prepared from the cerebellum.
In previous work we showed that phosphorylation of glial fibrillary acidic protein (GFAP), an astrocyte marker, is increased by glutamate in hippocampal slices from immature rats via a type II metabotropic receptor. In the present work we show that glutamate also stimulates GFAP phosphorylation in microslices prepared from immature cerebellar cortex, but by a different receptor mechanism from that observed in the hippocampus. Thus, in cerebellar microslices, NMDA consistently stimulated GFAP phosphorylation, whereas no effect of metabotropic or non-NMDA ionotropic agonists was observed. Glutamate and NMDA also stimulated GFAP phosphorylation in mixed neuronal/glial cell cultures from the cerebellum, although no effect of these agonists was observed in primary cultures of cerebellar astrocytes. In both models, the effects of glutamate and NMDA were dependent on external Ca(2+), were reversed by the NMDA receptor antagonist AP5 and were not blocked by tetrodotoxin. In the slice study the effect of NMDA was confined to a period starting with the first detectable expression of GFAP at 10 days and finishing at 16 days postnatal, as previously observed with metabotropic agonists in hippocampal slices. This period in the rat corresponds to the start of synaptogenesis when astrocyte hypertrophy is occurring. The results are discussed in the light of information in the literature on the occurrence of functional NMDA receptor subunits in glia.
Kommers
Trícia
T
Departamento de Bioquímica, ICBS, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2600, Anexo 90035003, RS, Porto Alegre, Brazil.
Rodnight
Richard
R
Boeck
Carina
C
Vendite
Deusa
D
Oliveira
Diogo
D
Horn
Joel
J
Oppelt
Daniela
D
Wofchuk
Susana
S
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D018920:Coculture Techniques; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D007382:Intermediate Filaments / Q000187:drug effects / Q000378:metabolism; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D005904:Glial Fibrillary Acidic Protein; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D016202:N-Methylaspartate