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-hydro xy-5-methylisoxazole-4-pr acid (AMPA) antagonists were studied on resp onses of single neurones to iontophoretically applied excitatory amino acids. The tests were performed on spinal neurones in alpha-chloralos e anaesthetized, spinalized rats. 2 Both the quinoxaline, NBQX (2-16 m g 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 a cting, 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 fo r either systemic GYKI 53655 or iontophoretic NBQX, suggesting that sy stemic NBQX may be converted to a less selective metabolite. 5 GYKI 53 655 is therefore likely to be a more valuable tool than NBQX for the s tudy of AMPA receptor-mediated processes in vivo.