Figure 6.

Temperature dependence of single-channel Ca²⁺ signals. (A) Representative fluorescence traces recorded at nine sites showing single-channel IP₃R signals (blips), at temperatures of 12°C, 22°C, and 36°C. (B) Plots of mean blip durations, derived as arithmetic means (solid squares) and from exponential fits to distributions (open circles), as functions of temperature. The Arrhenius plot is fitted by segmental linear regression (transition point at 25.1°C). (C) Inset traces illustrate dwell-state levels visually identified on the stepwise falling phase of puffs (upper), and single-channel blips (lower) at temperatures of 12°C, 22°C, and 36°C. The histograms show the corresponding distributions of dwell-state amplitude levels during puffs. The data (>1230 measurements at each temperature) are fit by sums of multiple Gaussian functions, as shown by smooth curves. (D) Plot of center values of the Gaussian fits as a function of the ordinate number of each Gaussian (i.e., the first, second, third, etc. Gaussian, in ascending order). Points show measurements at temperatures of 12°C (open triangles), 22°C (solid circles), and 36°C (open squares). Error bars: mean ± 1 SE of the Gaussian fits. The line is a regression fit to the entire data set.