2-3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline and Neurodegenerative-Diseases

The involvement of alpha-amino-3-hydroxy-5-methylizoxazole-4-propionic acid (AMPA) receptors in induction of long-term potentiation (LTP) was examined in rat hippocampal slice preparation. Using conventional extracellular recording, excitatory postsynaptic potentials (EPSPs) and population action potentials (PSs), evoked by low-frequency stimulation of the Schaffer collateral-commissural fibres, were recorded in the CA1 region. The effects of a competitive AMPA receptor antagonist, 6-nitro-7-sulfamoylbenzo(f)quinoxaline-2, 3-dione (NBQX), and that of a non-competitive blocker, 1-(4-aminophenyl)-4-methyl-7,8-methylendioxy-5H-2,3-benzodiazepine (GYKI 52466) have been examined. 0.25-0.5 microM of NBQX and 20-40 microM of GYKI 52466 did not suppress the induction of LTP. LTP was attenuated only at the highest concentrations tested (1 microM NBQX or 80 microM GYKI 52466). These in vitro concentrations, however, exceed the brain levels needed for in vivo anticonvulsant action. Furthermore, even at the highest concentrations both compounds suppressed only the expression but not the induction of LTP. Namely after their washout LTP reappeared. Thus, at pharmacologically relevant concentrations these AMPA receptor antagonists apparently do not suppress LTP, a cellular mechanism underlying memory formation. These experiments suggest that in clinical practice AMPA receptor blockade may have some advantage over N-methyl-D-aspartate receptor antagonism, which is accompanied by severe memory impairment.

Topics: Animals; Anti-Anxiety Agents; Benzodiazepines; Dose-Response Relationship, Drug; Epilepsy; Excitatory Amino Acid Antagonists; Excitatory Postsynaptic Potentials; Hippocampus; Long-Term Potentiation; Male; Memory; Neurodegenerative Diseases; Neurons; Organ Culture Techniques; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, AMPA