Figure 3.

a, Averaged fluo-4 fluorescence traces for hippocampal neurons (n = 100 neurons for each trace) following 50 μM CORM-2 (blue) or 50 μM RuCl₃ (green) infusion at 30 s (dashed lines). The solid lines and shaded areas represent the mean and s.e.m., respectively. b, Time-lapse images of Ca²⁺ responses in response to CORM-2 infusion (scale bar, 50 μm). c, CORM-2 concentration-dependent maximum of normalized fluo-4 fluorescence change averaged across 100 neurons. d, Maximum of normalized fluo-4 fluorescence increases in 100 neurons following the infusion of 50 μM CORM-2 in the presence or absence of L-type Ca²⁺ channel blocker nitrendipine. e, A schematic illustrating a potential mechanism of CO-mediated Ca²⁺ responses in neurons through L-type Ca²⁺ channel. f, Experimental scheme for electrochemical CO delivery to neurons. g, Time-lapse images of Ca²⁺ increases in neurons triggered by CO produced from CoPc/OxCP cathodes, which were positioned at the left edge in all three images, at −1.3 V versus SHE (scale bar, 50 μm). Neurons located at greater distances from the cathode responded over time (white dotted circles). h-j, Individual fluo-4 fluorescence traces for 100 neurons at different experimental conditions. E-field (–) in (i) represents neurons immersed in CO₂-saturated solution in the absence of an applied voltage. CO_2(aq) (–) in (j) represents neurons immersed in Tyrode’s not saturated in CO₂ in the presence of an applied voltage (j). Voltage of −1.3 V were turned on at 30 s (dashed lines) in h and j. k-l, Individual fluo-4 fluorescence traces for 100 neurons after electrochemical CO generation at −0.9 V (k) and −1.7 V versus SHE (l). Voltages were turned on at 30 s (dashed lines).