AMPA-induced Ca 2+ influx in cultured rat cortical nonpyramidal neurones: pharmacological characterization using fura-2 microfluorimetry

Abstract

Immunocytochemical and Co 2+ uptake studies revealed that in primary cultures of rat cortical neurones, the majority of neurones are γ-aminobutyric acid (GABA) immunopositive and can express Ca 2+-permeable α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors. By fura-2 microfluorimetry, it was shown that the stimulation with the selective agonist ( S)-AMPA (0.3–300 μM) induced a concentration-dependent but cell-variable increase in intracellular Ca 2+ concentration ([Ca 2+] i) (EC 50 value 7.4 μM) in more than 80% of the medium-sized multipolar neurones studied. The AMPA-induced rise in [Ca 2+] i seems to be due to Ca 2+ entry through AMPA receptor channels, because the response was abolished in Ca 2+-free solution and by AMPA receptor selective antagonists, but was not significantly influenced by cyclopiazonic acid, an inhibitor of the endoplasmatic Ca 2+-ATPase, by selective N-methyl- d-aspartic acid (NMDA) receptor antagonists, as well as the Na + channel blocker tetrodotoxin and the majority of tested Ca 2+ channel blockers. In conclusion, the results indicate that the cerebral cortical neurones in culture represent mostly GABAergic interneurone-like cells and the majority of them possess Ca 2+-permeable AMPA receptors, important for intracellular signal transduction and neuronal plasticity.