Inhibition of α-subunit glycine receptors by quinoxalines

Abstract
Quinoxalines are widely used compounds in electrophysiological studies to separate excitatory and inhibitory neurotransmission mediated by the strychnine-insensitive and strychnine-sensitive glycine receptor (NMDA, GlyR), respectively. We report here, that the quinoxaline NBQX is a potent antagonist of homo-oligomeric alpha1- and alpha2-subunit glycine receptors expressed in Xenopus laevis oocytes. NBQX elicited half-maximal inhibition of glycine evoked currents at a concentration of about 5 microM. DNQX and CNQX were found to be 5-fold and 20-fold less efficient than NBQX. At oocytes expressing alpha1beta2 subunit GABAA receptors the quinoxalines tested showed no significant inhibition of GABA responses up to a concentration of 100 microM. Our data indicates that these quinoxalines applied at concentrations sufficient to block NMDA receptor also attenuate GlyR responses.

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