SELECTIVE MODULATION OF DESENSITIZATION AT AMPA VERSUS KAINATE RECEPTORS BY CYCLOTHIAZIDE AND CONCANAVALIN-A

Potentiation by cyclothiazide of recombinant glutamate receptor respon ses in Xenopus oocytes showed absolute selectivity for AMPA versus kai nate receptors. In contrast, concanavalin A strongly potentiated respo nses at kainate but not AMPA receptors. Rapid desensitization in HEK 2 93 cells transfected with AMPA receptors was blocked by cyclothiazide, but only weakly attenuated by concanavalin A. Desensitization at kain ate receptors was blocked by concanavalin A but unaffected by cyclothi azide. Selective effects of these modulators following coexpression of subunits from different families suggest independent assembly of func tional AMPA and kainate receptors. Northern biot analysis of mRNA for dorsal root ganglia revealed a predominant expression of GluR5, indica ting that modulation of desensitization by concanavalin A but not cycl othiazide in sensory neurons accurately predicts subunit expression fo r native glutamate receptors.