Figure 12.

The effect of the morphology of the nociceptive terminal tree on the input-output properties of the primary nociceptive neuron. A figure summarizing the effect of the terminal structure on its function. Activation of all terminal branches in a simplified realistic terminal tree (all the terminal branches are of equal size of 75 µm, and they are evenly distributed along the degenerate and symmetrical parts of the complex terminal, black) by capsaicin-like stimulus led to the response whose gain (A, lower panels) and AP temporal pattern (B, C, showing the instantaneous frequency and spike raster plot, respectively) are dependent on the terminal morphologic characteristics, such as change in the number of terminal branches and the properties of the individual branch. The increase in the number of activated terminal branches (red) led to increased firing; the decrease in branching (blue) led to decreased firing. Terminal tree with short and thick (lower conductive part's Ra) terminal branches demonstrate lower gain (green), whereas a terminal tree with long terminals has a higher gain (orange). All the perturbations in terminal morphology change the timing pattern of firing (B, C).