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 p rotein (GFAP) in hippocampal slices from immature rats (10-16 days pos tnatal) 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-aminocyc lopentane-1,3-dicarboxylic acid (1S,3R-ACPD), stimulated GFAP phosphor ylation by 173% whilst the mixed agonists, ibotenate and quisqualate, stimulated to a lesser extent. Ionotropic agonists were mainly ineffec tive. The action of 1S,3R-ACPD was blocked by L(+)-2-amino-3-phosphono propionic acid (L-AP(3)) a specific antagonist of the metabotropic glu tamate receptor coupled to the hydrolysis of phosphoinositides and was reduced by 70% by preincubation of the slices with pertussis toxin. I n contrast to these results with immature animals glutamate had little or no effect on the phosphorylation of GFAP in hippocampal slices fro m adult rats.