Mn2+ Quench Experiment

Mn²⁺ can pass through opened Ca²⁺-permeable channels and quenches the Fura-2 LR fluorescence emission (Amano et al., 1997; Kikuta et al., 2015). Thus, to evaluate Ca²⁺ influx from the extracellular space, the rate of the quench by Mn²⁺ was quantified as Δ F/F at 380 nm (Uehara et al., 2002; Tu et al., 2009; Kikuta et al., 2015). To evaluate the influx rate of Mn²⁺, the time constant of quenching (τ_q) after MnCl₂ perfusion was calculated by fitting with the following equation:

where t is the time from the start of MnCl₂ administration, T is the time between the onset of recording and the start of MnCl₂ administration, A_b, τ_b, and B_b are amplitude, time constant, and baseline level of the fluorescence bleaching, respectively, and A_q, τ_q, and B_q are amplitude, time constant and baseline level of the fluorescence quenching, respectively. The curve fitting was performed using SciPlot (M. Wesemann, 1991–95).