Résumé
Most of the effects of excitatory amino acids (EAAs) have been attributed to their interactions with three main ionotropic receptors: the
N-methyl-
d-aspartate
(NMDA), the quisqualate (Q) and the kainate (K) receptors. In this review, we discuss data showing that in several experimental preparations (neuronal and glial cultures, brain slices, synaptoneurosomes), activation of EAA receptors stimulates the inositol phosphate (IP)/diacylglycerol (DAG) second messenger pathway, and that novel EAA receptors are implicated. They include Q- and ibotenate (IBO)-preferring receptors, which are potent stimulators of IP production, mobilize intra cellular Ca
2+ stores and have specificities distinct from other EAA receptors already described. The activity of this novel class of EAA receptors is high during the synaptogenesis period and low in adult brain. NMDA and K receptors also stimulate IP production, although this effect is probably indirect. The possible functions of EAA receptors associated with the production of IP/DAG are discussed.