AMPA (amino-3-hydroxy-5-methylisoxazole-4-propionic acid) Receptors in human brain tissues

Abstract

AMPA receptors may play an important role in acute and chronic neurodegenerative diseases. An assay for the specific binding of [³H]-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) to receptors in membranes from post-mortem human brain is described, which can be used in screening for selective AMPA receptor antagonists. Membranes were prepared from frozen human adult hippocampus and whole fetal brain tissues. [³H]-AMPA binding to human hippocampus was saturable; Scatchard analysis of equilibrium binding data indicated high and low affinity sites with affinity binding constants (K_D) of 3.4 ± 0.5 nM and 65 ± 9 nM (n=7) respectively. Biphasic association and dissociation rate constants for [³H]-AMPA binding were consistent with the biphasic Scatchard analysis. Inhibition of [³H)-AMPA binding revealed a rank order of potency as quisqualate = AMPA > BOAA > L-glutamate = DNQX = CNQX > kainate > L-aspartate = NMDA. AMPA receptors in human fetal brain had a comparable pharmacology. AMPA/kainate receptors were expressed in frog oocytes following injection of RNA prepared from human fetal brain. Human brain tissues may therefore be utilized for screening and functional analysis of AMPA receptor antagonists.