Effect of temperature increase on presynaptic excitation. A) Pseudo-color image sequence of stimulation-induced optical responses measured in the solution at 27°C, 33°C, and 27°C in a slice (from left to right). B) Superimposed time traces of optical signals obtained at 27°C (black), 33°C (dashed black), and 27°C (red). These records were obtained by spatial average of the optical signals of 8 × 8 pixels corresponding to a black square area (50 × 50 μm) shown in the schematic drawing of the dorsal horn. Dotted line in the optical signal records indicates the baseline level. C) Spatial distributions of the magnitude of excitation along dorso-ventral lines a, b and c in schematic drawing. D) Normalized time course of magnitude of optical signals showing the averaged effect induced by a change of temperature from 27°C to 33°C.