Abstract
Lucifer Yellow CH (LY), a fluorescence dye, has been injected into cells examined electrophysiologically in order to visualize them. We had reported that LY had blocked the inactivation of voltage-gated Na+ channel currents in a light-dependent manner and suggested that LY radicals generated by illumination modified channel proteins (J. Physiol, 2003). In this study, we investigated the effect of LY on other voltage-gated currents (delayed rectifier, inward rectifier K+, Cl−, HVA-Ca2+ currents) and ligand-gated currents (NMDA, AMPA, kainite, 5HT3, and GABAA receptor currents) of cultured mouse hippocampal neurons under voltage-clamp conditions. LY applied inside cells irreversibly blocked the steady state inactivation of AMPA receptor currents upon a few minutes exposure to light of usual intensity for microscopy. The pre-treatment of cells with 1 mM dithiothreitol antagonized the LY effect. The reversal potential of the steady state inactivation currents remained unchanged, indicating LY hardly changed the ionic selectivity of AMPA receptors. LY also increased the magnitude of delayed rectifier and inward rectifier K+ currents that a little inactivated in a light-dependent manner. LY had no effects on other voltage-gated and ligand-gated currents, including rapid inactivating 5HT3 receptor currents. These results suggest that LY radicals produced by the exposure oxidize the cytoplasmic loops of AMPA receptors responsible for the steady state inactivation with a moderate selectivity. [Jpn J Physiol 55 Suppl:S139 (2005)]
