Effect of Mg2+ on Neural Activitiy


Keiichi Torimitsu
Materials Science Laboratory

 It is well known that magnesium ion (Mg2+) plays an important role in biological functions, similar to that of calcium ion (Ca2+). It would be useful to understand the effect of Mg2+ on neural functions in relation to controlling neural activity. However, the relationship between Mg2+ and neural functions has not been well understood. Although recent studies indicate that an Mg2+ deficient diet has significant health effects, few reports have studied the effect of Mg2+ on neural activity [1]. Here we have investigated the effect of low concentrations of extracellular Mg2+ on membrane potential using flow cytometry, and on the intracellular Ca2+ concentration using a confocal laser microscope.
 Figure 1 shows the Mg2+ dependence on the membrane potential of cortical neurons. Oxyonol dye DiBAC4(3) was used for the measurements. The results indicate that a low Mg2+ concentration depolarizes the membrane potential depending on the reduction in the extracelluar Mg2+ concentration below 2 mM [2, 3]. The developmental effect of Mg2+ was significant at 12 days in vitro (DIV), and could be observed at a concentration of less than 0.7 mM (Fig. 2) [2, 3].
 The same type of Mg2+ dependence was observed in hippocampal neurons. However, the responses of cortical and hippocampal neurons to a low Mg2+ concentration differed during the developmental period. The results indicate that hippocampal neurons are more sensitive to Mg2+ than cortical neurons. This may originate in the difference in the receptor distribution in those regions [3]. Further investigation is needed to understand the mechanisms of the Mg2+ effect on neural activity.

[1] K.Torimitsu, N. Kasai, and Y. Furukawa, Clin. Calcium 14 (2004) 26.
[2] Y. Furukawa and K. Torimitsu, JJSMgR 27 (2008) 75.
[3] Y. Furukawa, N. Kasai, and K. Torimitsu, Magnes. Res. 22 (2009) 174S.

Fig..1. Magnesium dependence of membrane potential
in cortical neurons.
Fig..2. Developmental effect of magnesium on
intracellular Ca2+ concentrations.

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