Figure 11.

In modeled inflammatory and neuropathic conditions, the change in response is encoded by alteration in the temporal pattern of the spike trains. A, Scheme of the experiment: in normal condition, the SIZ is located 25 µm from the terminal end, and the terminal membrane potential is quiescent. The inflammatory hyperalgesia is modeled by shifting the SIZ 5 µm toward the terminal tip. The neuropathic hyperalgesia is modeled by injected to the model subthreshold or suprathreshold current noise (see Materials and Methods). Insets, Recording of the membrane voltage following the application of subthreshold and suprathreshold noise. B, Responses detected at the central terminals following activation of all terminal branches by a capsaicin-like current in normal conditions (black), in the conditions of inflammatory hyperalgesia (red), and in conditions of the neuropathic hyperalgesia with the injection of subthreshold noise (purple) and suprathreshold noise (orange). The AP count was performed for a first 5 s after a capsaicin-like current application (outlined by the dashed-line rectangle). Inset, Superimposition of the traces obtained in normal conditions and in the inflammatory hyperalgesia conditions at the time outlined by the gray dashed-line rectangle. Note the difference in the pattern of firing. C, Instantaneous discharge frequencies following stimulation with a capsaicin-like current (shown below) applied to all terminal branches in normal conditions (black), in the conditions of inflammatory hyperalgesia (red), and in the conditions of neuropathic hyperalgesia with the injection of subthreshold noise (purple) and suprathreshold noise (orange). Insets, Expanded x-axis. D, Spike raster plot showing the AP timing, following stimulation of all terminal branches with a capsaicin-like current, in normal conditions (black), in the conditions of the inflammatory hyperalgesia (red), and in the conditions of the neuropathic hyperalgesia with the injection of subthreshold noise (purple) and suprathreshold noise (orange). Insets, Expanded x-axis. The data describing the normal conditions are taken from Figure 1 and showed here for better comparison.