Characterization and regulation of a high affinity [ 3H]CNQX labelled AMPA receptor in rat neocortex

Abstract

We have characterized a high affinity site of the α-amino-3 hydroxy-5-methyl-isoxasole-4-propionate (AMPA) receptor in in vitro living slices of adult rat neocortex using [ 3H]CNQX, an AMPA antagonist. [ 3H]CNQX labelled multiple binding sites with a B max of a high affinity site of approximately 470 fmol/mg protein and an apparent K d of 11.3 nM. The high affinity site of the AMPA receptor could be down-regulated (36%) by 2 h preincubations in quisqualate, an AMPA agonist. Increases in electrical activity induced by a combination of veratridine and glutamate also led to an average decrease of the high affinity AMPA receptor number of 17%. In addition, preincubations with muscimol, a GABA A agonist, as well as glutamate agonists kainate and N- methyl- d-aspartate (NMDA) led to an average increase in high affinity AMPA receptor number of 17%, 14%, and 37%, respectively. The present results show that a ligand-gated high affinity AMPA receptor can be regulated by agonist stimulation as well as changes in neural activity.