title: Effects of 4-aminopyridine on organelle movement in cultured mouse dorsal root ganglion neurites.
abstract: Aminopyridines, widely used as a K(+) channel blocker, are membrane-permeable weak bases and have the ability to form vacuoles in the cytoplasm. The vacuoles originate from acidic organelles such as lysosomes. Here, we investigated the effects of 4-aminopyridine (4-AP) on organelle movement in neurites of cultured mouse dorsal root ganglion (DRG) neurons by using video-enhanced microscopy. Some experiments were carried out using fluorescent dyes for lysosomes and mitochondria and confocal microscopy. Treatment of DRG neurons with 4 mM 4-AP caused Brownian movement of some lysosomes within 5 min. The Brownian movement gradually became rapid and vacuoles were formed around individual lysosomes 10-20 min after the start of treatment. Axonal transport of organelles was inhibited by 4-AP. Lysosomes showing Brownian movement were not transported in longitudinal direction of the neurite and the transport of mitochondria was interrupted by vacuoles. The 4-AP-induced Brownian movement of lysosomes with vacuole formation and inhibition of axonal transport were prevented by the simultaneous treatment with vacuolar H(+) ATPase inhibitor bafilomycin A1 or in Cl(-)-free SO(4)(2-) medium. These results indicate that changes in organelle movement by 4-AP are related to vacuole formation and the vacuolar H(+) ATPase and Cl(-) are required for the effects of 4-AP.
authors.affiliation: Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, 228-8555, Japan. hiruma@med.kitasato-u.ac.jp
authors.forename: Hiromi
authors.initials: H
authors.lastname: Hiruma
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kawakami
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D005727:Ganglia, Spinal / Q000166:cytology*; D018942:Macrolides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018715:Microscopy, Video; D016501:Neurites / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D015388:Organelles / Q000187:drug effects / Q000502:physiology; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D018942:Macrolides; D026902:Potassium Channel Blockers; C057620:bafilomycin A; D015761:4-Aminopyridine; D025262:Vacuolar Proton-Translocating ATPases