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Fig. 2 | Journal of Biomedical Science

Fig. 2

From: Differential regulation of nimodipine-sensitive and -insensitive Ca2+ influx by the Na+/Ca2+ exchanger and mitochondria in the rat suprachiasmatic nucleus neurons

Fig. 2

Nimodipine effects on high K+-induced Ca2+ transients. a A representative experiment to show the averaged Ca2+ response (n = 20 cells) to 10 s application of high K+ (20, 35, and 50 mM) solutions in the absence and then presence of 2 μM nimodipine. The K+-free (0-K+) solution (to block Na/K pump) was applied first to determine the condition of reduced SCN preparations and to confirm the cells being recorded are indeed neurons. b Averaged Ca2+ responses to 20, 35, and 50 mM K+ solution in control (top panel) and in the presence of 2 μM nimodipine (middle panel). Bottom panel shows the nimodipine-sensitive Ca2+ responses after subtraction. The peak amplitude of Ca2+ transients increased with higher K+ concentrations as expected. Note the much larger Ca2+ response to 20 mM K+ for nimodipine-sensitive (bottom left panel) than the nimodipine-insensitive (middle left panel) component. c Statistics showing the percent block by 2 μM nimodipine of peak Ca2+ responses to increasing concentrations of K+. d Superimposition of nimodipine-sensitive 20 K+- and 50 K+-induced Ca2+ transients for curve fitting. The grey curve for fitting the decay phase of 20 K+-induced Ca2+ transient was calculated with only the fast exponential decay phase, whereas the black curve for the 50 K+-induced Ca2+ transient was calculated with both the fast and slow exponential decay phases. e Comparison of nimodipine-sensitive (black) and -insensitive (grey) Ca2+ responses to 50 mM K+. Note the faster rate of Ca2+ rise to reach a steady state during the 10-s stimulation by 50 mM K+ for the nimodipine-sensitive component Ca2+ transient. Nevertheless, both components decayed in a similar way, having both a fast and slow time course, suggesting a similar mechanism for Ca2+ clearance. *** P < 0.001

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