Figure 1

Increase in net neuronal excitation in the spinal dorsal horn following application of picrotoxin. A, Optical responses elicited by a high-intensity single-pulse stimulation (a current pulse of 2.0 mA with a duration of 0.5 ms) to the dorsal root in the control condition (left image) and in the presence of picrotoxin (right image) 4.8 ms after stimulation. Images were taken from the area indicated by the red square in the photo of the transverse slice. The percent change in light absorption is depicted using simulated color as described in the color bar. B, Spatial distributions of the optical responses in the control (thin lines) and picrotoxin (bold lines) conditions along three dorso-ventral lines, a-c, in the photo of a transverse slice indicated in A. Horizontal bars indicate the area of the substantia gelatinosa (SG) identified visually. C, Spatially averaged time courses of responses in control (thin line) and picrotoxin (bold line) conditions. The time courses were obtained in the dorsal horn from the area indicated by the filled white square in the photo of a transverse slice indicated in A. D, Optical responses elicited by a low-intensity single-pulse stimulation (a current pulse of 1.0 mA with a duration of 0.5 ms) to the dorsal root in control (left image) and picrotoxin (right image) conditions 4.8 ms after stimulation. Images were taken from the area indicated by the red square indicated in A. The percent change in the light absorption is depicted using simulated color as described in the color bar. E, Spatially averaged time courses of responses in control (thin line) and picrotoxin (thick line) conditions. The time courses were obtained in the dorsal horn from the area indicated by the filled white rectangle indicated in A.