(S)-homoquisqualate: a potent agonist at the glutamate metabotropic receptor.

The synthetic quisqualate analogue, (S)-homoquisqualate was examined for activity at the glutamate metabotropic receptor, in relation to its ability to stimulate phosphoinositide hydrolysis in rat pup cerebro-cortical slices. The compound produced a robust increase in hydrolysis (EC50 = 50.2 +/- 1.6 microM), which, in common with responses to quisqualate and (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate ((1S,3R)-ACPD), was antagonized uncompetitively by L-2-amino-3-phosphonopropionate (L-AP3). In contrast to quisqualate which exhibits low efficacy, (S)-homoquisqualate behaves as a full agonist at the metabotropic receptor.