GLUTAMATE METABOTROPIC RECEPTOR ACTIVATION IN NEONATAL RAT CEREBRAL-CORTEX BY SULFUR-CONTAINING EXCITATORY AMINO-ACIDS

The sulphur-containing acidic amino acids (SAAs) display neuroexcitato ry actions similar to those Of L-glutamate and are widely regarded as bona fide transmitter candidates. In this study, L-cysteine sulphinic acid, L-Cysteic acid, DL-homocysteine acid ard L-homocysteine sulphini c acid were investigated for their ability to stimulate phosphatidylin ositol hydrolysis in rat pup cerebrocortical slices and compared with L-glutamate and the selective agonist (I S,3R)-1-aminocyclopentane- 1, 3-dicarboxylic acid ((l S,3R)-ACPD). Each of the SAAs possessed agonis t activity at metabotropic glutamate receptors (mGluRs) and, although they exhibited lower efficacy than L-glutamate, they were more potent (EC55s of 401-487 muM compared with 791 muM for L-glutamate). These da ta are consistent with the possibility that SAAs may have a physiologi cal role as endogenous activators of metabotropic (and presumably iono tropic) excitatory amino acid receptors.