Glutamate stimulates the phosphorylation of glial fibrillary acidic protein in slices of immature rat hippocampus via a metabotropic receptor.

Phosphorylation of the astrocyte cell marker glial fibrillary acidic protein (GFAP) in hippocampal slices from immature rats (10-16 days postnatal) was strongly stimulated by glutamate in the presence of Ca2+. This effect apparently occurred via a metabotropic receptor since the specific agonist of metabotropic glutamate receptors, 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD), stimulated GFAP phosphorylation by 173% whilst the mixed agonists, ibotenate and quisqualate, stimulated to a lesser extent. Ionotropic agonists were mainly ineffective. The action of 1S,3R-ACPD was blocked by L(+)-2-amino-3-phosphonopropionic acid (L-AP3) a specific antagonist of the metabotropic glutamate receptor coupled to the hydrolysis of phosphoinositides and was reduced by 70% by preincubation of the slices with pertussis toxin. In contrast to these results with immature animals glutamate had little or no effect on the phosphorylation of GFAP in hippocampal slices from adult rats.