Abstract
Lucifer Yellow (LY) has been used to mark cells electrophysiologically investigated or to visualize coupled cells with gap junctions. We, however, showed that LY radicals produced by the illumination of LY with the moderate intensity light inhibited the inactivation of voltage-gated Na+ channels by increasing the mean open time of the channel (J. Physiol., 550.1;159-167, 2003). In the present study, we investigated the effect of illuminated LY (2 mg/ml) on voltage-gated K+ channels and on ligand-gated channels of cultured hippocampal neurons under whole-cell clamp conditions. The light was 4850 lx at source, a moderate strength for microscopy, and band-passed (400-440 nm). The width of action potentials increased with increasing exposure time, and was 3.9 times longer than the control after 5 min exposure. After 4 min exposure, the magnitude of delayed rectifier K+ currents was 1.4 times larger than the control at +65.3 mV, and that of inward rectifier K+ currents was 1.6 times larger at –134.7 mV. The pretreatment of LY-injected neurons with 1 mM dithiothreitol for 10 min inhibited the elongation of action potential width and the enhancement of both K+ current in magnitude. In contrast, exposed LY hardly changed the magnitude of NMDA- and GABA-induced currents. These results suggest that LY radicals modify a part or parts of voltage-gated channel proteins that regulate the channel open times. [Jpn J Physiol 54 Suppl:S133 (2004)]
