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 receptors in the control of glutamate release from cerebrocortical nerve terminals. The metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid enhances the release evoked by a submaximal depolarization in the presence of low concentrations of arachidonic acid and in a staurosporine-sensitive manner. In contrast, (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid and L(+)-2-amino-4-phosphonobutyrate inhibit the release evoked by a maximal depolarization, in the absence of arachidonic acid and by a staurosporine-insensitive mechanism. Interestingly, the effects of the metabotropic glutamate receptors that inhibit glutamate release are only observed in the nerve terminals from young rats (one to three weeks), while the facilitatory effects are better seen in latter developmental stages (three to four weeks) and adult (two to three months) rats, coinciding with the development of the maximal capacity of glutamate uptake. These results indicate the existence of important developmental changes in the presynaptic control of glutamate release.