title: Neural depolarization triggers Mg2+ influx in rat hippocampal neurons.
abstract: Homeostasis of magnesium ion (Mg(2+)) plays key roles in healthy neuronal functions, and deficiency of Mg(2+) is involved in various neuronal diseases. In neurons, we have reported that excitotoxicity induced by excitatory neurotransmitter glutamate increases intracellular Mg(2+) concentration ([Mg(2+)]i). However, it has not been revealed whether neuronal activity under physiological condition modulates [Mg(2+)]i. The aim of this study is to explore the direct relationship between neural activity and [Mg(2+)]i dynamics. In rat primary-dissociated hippocampal neurons, the [Mg(2+)]i and [Ca(2+)]i dynamics were simultaneously visualized with a highly selective fluorescent Mg(2+) probe, KMG-104, and a fluorescent Ca(2+) probe, Fura Red, respectively. [Mg(2+)]i increase concomitant with neural activity by direct current stimulation was observed in neurons plated on an indium-tin oxide (ITO) glass electrode, which enables fluorescent imaging during neural stimulation. The neural activity-dependent [Mg(2+)]i increase was also detected in neurons whose excitability was enhanced by the treatment of a voltage-gated K(+) channel blocker, tetraethylammonium (TEA) at the timings of spontaneous Ca(2+) increase. Furthermore, the [Mg(2+)]i increase was abolished in Mg(2+)-free extracellular medium, indicating [Mg(2+)]i increase is due to Mg(2+) influx induced by neural activity. The direct neuronal depolarization by veratridine, a Na(+) channel opener, induced [Mg(2+)]i increase, and this [Mg(2+)]i increase was suppressed by the pretreatment of a non-specific Mg(2+) channel inhibitor, 2-aminoethoxydiphenyl borate (2-APB). Overall, activity-dependent [Mg(2+)]i increase results from Mg(2+) influx through 2-APB-sensitive channels in rat hippocampal neurons.
authors.affiliation: Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan. Electronic address: 1024mbmail@gmail.com.
authors.forename: R
authors.initials: R
authors.lastname: Yamanaka
authors.affiliation: Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan. Electronic address: shindo@z5.keio.jp.
authors.forename: Y
authors.initials: Y
authors.lastname: Shindo
authors.affiliation: Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Karube
authors.affiliation: Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan. Electronic address: khotta@bio.keio.ac.jp.
authors.forename: K
authors.initials: K
authors.lastname: Hotta
authors.affiliation: Center for Science and Technology for Designing Functions, School of Integrated Design Engineering, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan. Electronic address: suzuki@applc.keio.ac.jp.
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa 223-8522, Japan. Electronic address: oka@bio.keio.ac.jp.
authors.forename: K
authors.initials: K
authors.lastname: Oka
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004558:Electric Stimulation; D006624:Hippocampus / Q000378:metabolism / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism*; D008564:Membrane Potentials; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D008274:Magnesium; D002118:Calcium
keywords: ITO electrode; KMG-104; Mg(2+); depolarization; fluorescent imaging; hippocampal neuron