GUANINE-NUCLEOTIDES INHIBIT THE STIMULATION OF GFAP PHOSPHORYLATION BY GLUTAMATE

PHOSPHORYLATION of the astrocytic marker protein glial fibrillary acid ic protein (GFAP) in hippocampal slices from immature rats is stimulat ed by glutamate agonists via a metabotropic receptor. In this study we investigated the modulation of this stimulation by guanine nucleotide s. Recent work has shown that guanine nucleotides inhibit the binding of kainate to its receptors in a manner independent of G proteins. Gpp (NH)p, GDP-beta-S and GMP inhibited by approximately 50% the stimulati on of GFAP phosphorylation by glutamate or 1S,3R-ACPD. In the case of glutamate and Gpp(NH)p it was shown that the inhibition was dose depen dent. These results indicate that guanine nucleotides can inhibit glut amate-stimulated phosphorylation responses by interaction with a cell surface metabotropic receptor.