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The four stereoisomers of 5-(2-amino-2-carboxyethyl)-4,5-dihydroisoxazole-3-carboxylic acid(+)-4, (-)-4, (+)-5, and (-)-5 were prepared by stereoselective synthesis of two pairs of enantiomers, which were subsequently resolved by enzymatic procedures. These four stereoisomers and the four stereoisomers of the bicyclic analogue 5-amino-4,5,6,6a-tetrahydro-3aH-cyclopenta[d]isoxazole-3,5-dicarboxylic acid (+)-2, (-)-2, (+)-3, and (-)-3 were tested at ionotropic and metabotropic glutamate receptor subtypes. The most potent NMDA receptor antagonists [(+)-2, (-)-4, and (+)-5] showed a significant neuroprotective effect when tested in an oxygen glucose deprivation (OGD) cell culture test. The same compounds were preliminarily assayed using Xenopus oocytes expressing cloned rat NMDA receptors containing the NR1 subunit in combination with either NR2A, NR2B, NR2C, or NR2D subunit. In this assay, all three derivatives showed high antagonist potency with preference for the NR2A and NR2B subtypes, with derivative (-)-4 behaving as the most potent antagonist. The biological data are discussed on the basis of homology models reported in the literature for NMDA receptors and mGluRs.

To confirm previous reports on dexamethasone and sulfite neurotoxicity, and to investigate methylprednisolone, dopamine, and dobutamine neurotoxicity.Pure dexamethasone, injectable dexamethasone containing sodium metabisulfite (Soludecadron), pure methylprednisolone, injectable methylprednisolone (Solu-Medrol), pure dopamine, injectable dopamine containing potassium metabisulfite (Revivan), pure dobutamine, injectable dobutamine containing sodium metabisulfite (Dobutrex), and sodium metabisulfite were added to the medium of mixed glial-neuronal cell cultures at concentrations of 0.1, 1, 10, and 100 microM. Cell damage induced by glucocorticoids was assessed by measuring the release of lactate dehydrogenase (LDH) from the injured cells into the extracellular fluid during the 24 hours of exposure to drugs. Cell damage induced by catecholamines was assessed using the fluorescent dye propidium iodide (PI) method 24 hours after exposure to the drugs.Methylprednisolone and Solu-Medrol did not affect neuronal death, which was increased by dexamethasone and Soludecadron at 100 microM and sodium metabisulfite at 10 and 100 microM. Neuronal death was significantly increased by dopamine, Revivan, dobutamine, Dobutrex, and sulfites at 10 and 100 microM concentrations.In vitro dexamethasone, Soludecadron, and sulfites increase neuronal cell death, while methylprednisolone and Solu-Medrol are not neurotoxic; dopamine and dobutamine were found neurotoxic independently from sulfite toxicity.