Fluorescence of individual granule cell somata equilibrated with 50 nm TMRM⁺ in response to mitochondrial inhibition; curve fitting with the cell simulation. Ai–Ci, Granule cells were equilibrated with 50 nm TMRM⁺. Where indicated, 3 μm antimycin A (A), 5 μg/ml oligomycin (O), 2 μm rotenone (R), or 50 mm KCl (K) was added. The incubation medium contained 1.2 mm MgCl₂. Each trace is from a single representative soma. Aii–Cii, Values for Δψ_m (thin line) and Δψ_p(thick line) were obtained by curve fitting for the cell simulation. Aiii–Ciii, Cell simulation; total fluorescence (thin line) and mitochondrial component of fluorescence (thick line) are shown. The following parameters were used: matrix volume = 1% of cytoplasm; quench threshold = 50 μm; rate constant for plasma membrane equilibration = 0.003/sec (TMRM⁺).