[Physiological role of Mg2+ in neurons].

Physiological role of Mg ions in living cells is now in the process of reexamination. This is triggered by the finding that cytoplasmic Mg(2+) concentration measured by a fluorescent dye, mag fura-2, is surprisingly small, being not more than 1 mM. Lines of examination have revealed that Mg(2+) inhibits various species of ionc channels not only from outside but also from inside of the plasma membrane. Entry of Mg(2+) into intracellular space is revealed to take place via a Ca(2+)-channels, TRPM7; this channel may thus be called "Mg(2+)-channel". Moreover, an excess amount of intracellular Mg(2+) induced by hyper-activity of NMDA channels occasionally causes neuronal cell death as a result of inhibitory effects of Mg(2+) to mitochondrial activities.