Figure 3

Effect of temperature increase on C-fiber evoked net excitation. A) Pseudo-color image sequence of stimulation-induced optical responses measured in a slice in perfusion solution at 27°C, 33°C, 36°C, and 39°C (from left to right). Superimposed time traces of optical signals obtained at 27°C (thin black), 33°C (thin red), 36°C (bold black), and 39°C (dashed red). These records were obtained by spatial average of the optical signals of 8 × 8 pixels corresponding to the 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. B) Pseudo-color image sequence of stimulation-induced optical responses measured from slices bathed in 27°C, 33°C, and 27°C (form left to right). Superimposed time traces obtained at 27°C (thin black), 33°C (dashed black), and 27°C (red) are indicated at left below. Spatial distributions of the magnitude of excitation along lines in schematic drawing are illustrated at right below. C) Normalized time course of magnitude of optical signals showing the averaged effect induced by a change of temperature from 27°C to 33°C (left), and the averaged temperature-dependency of depression (right), in 4 slices.