1825114

Novel class of amino acid antagonists at non-N-methyl-D-aspartic acid excitatory amino acid receptors. Synthesis, in vitro and in vivo pharmacology, and neuroprotection.

Article date: 1991/1/1

PubMed ID: 1825114

Journal name: Journal of medicinal chemistry (ISSN: 0022-2623)

ABSTRACT

The isoxazole amino acid 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl) propionic acid (AMPA) (1), which is a highly selective agonist at the AMPA subtype of excitatory amino acid (EAA) receptors, has been used as a lead for the development of two novel EAA receptor antagonists. One of the compounds, 2-amino-3-[3-(carboxymethoxy)-5-methylisoxazol-4-yl]propionic acid (AMOA, 7), was synthesized via O-alkylation by ethyl chloroacetate of the amino acid protected AMPA derivative 4. The other compound, 2-amino-3-[2-(3-hydroxy-5-methylisoxazol-4-yl)-methyl-5-methyl-3-+ ++oxoisoxazolin -4-yl]propionic acid (AMNH, 14) was synthesized with use of 4-(chloromethyl)-3-methoxy-5-methylisoxazole (8) as the starting material. The intermediate 4-(chloromethyl)-2-(3-methoxy-5-methylisoxazol-4-yl)methyl-5-me thylisoxazolin- 3-one (11) was converted into the acetamidomalonate (12), which was stepwise deprotected to give 14. Compounds 7 and 14 were stable in aqueous solution at pH values close to physiological pH. Neither 7 nor 14 showed detectable affinities for the receptor, ion channel, or modulatory sites of the N-methyl-D-aspartic acid (NMDA) receptor complex. Quantitative receptor autoradiographic and conventional binding techniques were used to study the affinities of 7 and 14 for non-NMDA receptor sites. Both compounds were inhibitors of the binding of [3H]AMPA (IC50 = 90 and 29 microM, respectively). Compounds 14 and 7 were both very weak inhibitors of the high-affinity binding of radioactive kainic acid [( 3H]KAIN). Compound 14, but not 7, was, however, shown to be an inhibitor of low-affinity [3H]KAIN binding (IC50 = 40 microM) as determined in the presence of 100 mM calcium chloride. In the rat cortical slice preparation, 7 was shown to antagonize excitation induced by 1 with some selectivity, whereas 14 proved to be a rather selective antagonist of KAIN-induced excitation. Both antagonists showed very weak effects on the excitatory effects of NMDA. Compound 7 was a poor antagonist of excitation by quisqualic acid (2), whereas 14 did not affect excitation by this nonselective AMPA receptor agonist. On cat spinal neurones, both 7 and 14 reduced excitations by 1 and KAIN, but, again, the excitatory effects of 2 were much less sensitive. Compound 14 and, in particular, 7 effectively protected rat striatal neurones against the neurotoxic effects of KAIN, whereas the toxic effects of 1 were reduced only by 7. Neither antagonist showed protection against the cell damage caused by intrastriatal injection of the NMDA agonist quinolinic acid.(ABSTRACT TRUNCATED AT 400 WORDS)

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Author List: Krogsgaard-Larsen P, Ferkany J W, Nielsen E O, Madsen U, Ebert B, Johansen J S, Diemer N H, Bruhn T, Beattie D T, Curtis D R

Publication Types: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Substances mentioned in the article: Indicators and Reagents; Isoxazoles; Propionates; Receptors, N-Methyl-D-Aspartate; Tritium; 2-amino-3-(3-(carboxymethoxy)-5-methylisoxazol-4-yl)propionic acid; 2-amino-3-(2-(3-hydroxy-5-methylisoxazol-4-yl)methyl-5-methyl-3-oxoisoxazolin-4-yl)propionic acid; Ibotenic Acid; Dizocilpine Maleate; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Glycine;

Mesh terms: Animals; Autoradiography; Binding, Competitive; Brain/metabolism; Cerebral Cortex/drug effects; Dizocilpine Maleate/metabolism; Glycine/metabolism; Ibotenic Acid/analogs & derivatives; In Vitro Techniques; Indicators and Reagents; Isoxazoles/chemical synthesis; Male; Molecular Structure; Neurons/drug effects; Propionates/chemical synthesis; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate/drug effects; Structure-Activity Relationship; Tritium; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid;

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