POTASSIUM-INDUCED DEPOLARIZATION OF RAT TELENCEPHALIC SYNAPTONEUROSOMES INCREASES [H-3] AMINO-3-HYDROXY-5-METHYLISOXAZOLE-4-PROPIONATE RECEPTOR-BINDING

Potassium-induced depolarization of synaptoneurosomes prepared from rat telencephalon was found to increase [H-3]amino-3-hydroxy-5-methylisoxazole-4-propionate ([H-3]AMPA) binding to the AMPA receptor. The effect required the presence of calcium because it was blocked by the calcium chelator EGTA but was not blocked by an antagonist of the N-methyl-D-aspartate receptor, aminophosphonopentanoate. The depolarization-induced increase in [H-3]AMPA binding was markedly reduced by a blocker of voltage-dependent calcium channels, verapamil. Saturation kinetic experiments revealed that the increase in [H-3]AMPA binding produced by potassium depolarization was due to an increase in the affinity of the AMPA receptor. These results provide additional support for a critical role of calcium in the regulation of the AMPA receptors. The synaptoneurosome preparation might represent an interesting tool to determine the role of different calcium-dependent enzymes involved in the regulation of the AMPA receptor.