Lucifer Yellow slows voltage-gated Na+ current inactivation in a light-dependent manner in mice.
Lucifer Yellow CH (LY), a membrane-impermeant fluorescent dye, has been used in electro-physiological studies to visualize cell morphology, with little concern about its pharmacological effects. We investigated its effects on TTX-sensitive voltage-gated Na+ channels in mouse taste bud cells and hippocampal neurons under voltage-damp conditions. LY applied inside cells irreversibly slowed the inactivation of Na+ currents upon exposure to light of usual intensities. The inactivation time constant of Na+ currents elicited by a depolarization to -15 mV was increased by fourfold after a 5 min exposure to halogen light of 3200 Ix at source (3200 Ix light), and sevenfold after a 1-min exposure to 12,000 Ix light. A fraction of the Na+ current became non-inactivating following the exposure. The non-inactivating current was approximately 20 % of the peak total Na+ current after a 5 min exposure to 3200 Ix light, and approximately 30 % after a 1 min exposure to 12,000 Ix light. Light-exposed LY shifted slightly the current-voltage relationship of the peak Na+ current and of the steady-state inactivation curve, in the depolarizing direction. A similar light-dependent decrease in kinetics occurred in whole-cell Na+ currents of cultured mouse hippocampal neurones. Single-channel recordings showed that exposure to 6500 Ix light for 3 min increased the mean open time of Na+channels from 1.4 ms to 2.4 ms without changing the elementary conductance. The pre-incubation of taste bud cells with 1 mM dithiothreitoL a scavenger of radical species, blocked these LY effects. These results suggest that light-exposed LY yields radical species that modify Na+ channels.
Higure
Yoko
Y
Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka, Japan.
Katayama
Yoshimi
Y
Takeuchi
Keita
K
Ohtubo
Yoshitaka
Y
Yoshii
Kiyonori
K
D000818:Animals; D002478:Cells, Cultured; D004229:Dithiothreitol / Q000494:pharmacology; D004594:Electrophysiology; D005456:Fluorescent Dyes / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006706:Homeostasis; D015640:Ion Channel Gating / Q000502:physiology* / Q000528:radiation effects*; D007546:Isoquinolines / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008027:Light; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D015222:Sodium Channels / Q000502:physiology* / Q000528:radiation effects*; D013997:Time Factors
D005456:Fluorescent Dyes; D007546:Isoquinolines; D015222:Sodium Channels; C017475:lucifer yellow; D004229:Dithiothreitol