DEVELOPMENTAL-CHANGE FROM INHIBITION TO FACILITATION IN THE PRESYNAPTIC CONTROL OF GLUTAMATE EXOCYTOSIS BY METABOTROPIC GLUTAMATE RECEPTORS

We have addressed the role of presynaptic metabotropic glutamate recep tors in the control of glutamate release from cerebrocortical nerve te rminals. The metabotropic glutamate receptor agonist (1S,3R)-1-aminocy clopentane-1,3-dicarboxylic acid enhances the release evoked by a subm aximal depolarization in the presence of low concentrations of arachid onic acid and in a staurosporine-sensitive manner. In contrast, (1S,3R )-1-aminocyclopentane-1,3-dicarboxylic acid and L(+)-2-amino-4-phospho nobutyrate inhibit the release evoked by a maximal depolarization, in the absence of arachidonic acid and by a staurosporine-insensitive mec hanism. Interestingly, the effects of the metabotropic glutamate recep tors that inhibit glutamate release are only observed in the nerve ter minals from young rats (one to three weeks), while the facilitatory ef fects are better seen in latter developmental stages (three to four we eks) and adult (two to three months) rats, coinciding with the develop ment of the maximal capacity of glutamate uptake. These results indica te the existence of important developmental changes in the presynaptic control of glutamate release.