Fig. 1.
Pharmacological characterization of 0.1 mm[Mg2+]o-induced [Ca2+]i spiking in cultured rat hippocampal neurons. A, Stable [Ca2+]i spiking was induced by superfusion with 0.1 mm[Mg2+]o during the time indicated by the horizontal bar (n = 26). Note that the frequency of [Ca2+]i spiking was high initially, then decreased to become stable after 5 min of exposure to 0.1 mm[Mg2+]o. [Ca2+]i spiking required low Mg2+ buffer, because spiking disappeared when [Mg2+]o was restored to 0.9 mm. In separate experiments, CNQX (10 μm, n = 5) (B) and TTX (1 μm, n = 5) (D) blocked low [Mg2+]o-induced [Ca2+]i spiking completely, whereas CGS19755 (10 μm,n = 5) (C) inhibited, but did not completely block, spiking. Treatments were applied during the times indicated by the horizontal bars. Scale bars apply to all traces. Low [Mg2+]o was applied throughout the recordings shown inB–D.