A COMPARISON OF INTRAVENOUS NBQX AND GYKI-53655 AS AMPA ANTAGONISTS IN THE RAT SPINAL-CORD

1 The effects of intravenous administration of two alpha-amino-3-hydroxy-5-methylisoxazole-4-pr acid (AMPA) antagonists were studied on responses of single neurones to iontophoretically applied excitatory amino acids. The tests were performed on spinal neurones in alpha-chloralose anaesthetized, spinalized rats. 2 Both the quinoxaline, NBQX (2-16 mg kg(-1)) and the 2,3-benzodiazepine, GYKI 53655 (2-8 mg kg(-1)) dose-dependently decreased responses to AMPA. 3 Both compounds were short acting, with half-recovery times of 15 min for NBQX and 7 min for GYKI 53655. 4 The selectivity for responses to AMPA over those to. N-methyl-D-aspartate (NMDA) was significantly poorer for systemic NBQX than for either systemic GYKI 53655 or iontophoretic NBQX, suggesting that systemic NBQX may be converted to a less selective metabolite. 5 GYKI 53655 is therefore likely to be a more valuable tool than NBQX for the study of AMPA receptor-mediated processes in vivo.