Figure 5

NM-activated TRPM7 in hippocampal neurons depends on extracellular Ca²⁺ concentration. A, right, 10 mM Ca²⁺ blocks NM (200 μM)-induced TRPM7 current, n = 7. Left, high Ca²⁺ (10 mM) but not 2 mM Ca²⁺ occlude the TRPM7 activation by NM (200 μM), n = 6. B, left, NM elicited almost no current at 10 mM Ca²⁺ (with 1 mM Mg²⁺), small TRPM7 current at 2 mM Ca²⁺ (with 1 mM Mg²⁺) and large TRPM7 current at 0.1 Ca²⁺ (with 0.1 Mg²⁺) (n = 8). Right, bar graph shows statistics of NM-induced current at various Ca²⁺ conditions. The current amplitudes were 147 ± 20 pA at 10 mM Ca²⁺; 291 ± 52 pA at 2 mM Ca²⁺ and 1018 ± 120 pA at 0.1 mM Ca²⁺. C, TRPM7 current activated by NM was inhibited 97 ± 2% by Gd³⁺ (10 μM), n = 5. Left, current-trace example; right, bar graph showing statistics of current amplitude. D, NM-induced Ca²⁺ entry in hippocampal neurons is attenuated by high extracellular Ca²⁺. NM (200 μM)-induced Ca²⁺ entry monitored by Ca²⁺ imaging and high extracellular Ca²⁺ (5 mM) attenuated the Ca²⁺ entry. **, p < 0.01, 2 mM versus 5 mM Ca²⁺, n = 22. Bath solution contain no Mg²⁺ and MK801 (10 μM), CNQX (20 μM) and nimodipine (5 μM) was supplemented.