Figure 2.

Stimulation of multiple terminals allows summation of the voltage and facilitates nociceptive response. A, upper, Scheme depicting the experimental conditions: either one (blue) or both (red) 75-µm length terminal branches converging into the same convergence point in the symmetrical binary tree were stimulated by a capsaicin-like current. Lower, Resulted response recorded after the convergence point. Note that simultaneous activation of both terminals generated two APs (red trace), with higher after depolarization (inset). B, With all the Nav conductances annulled, activation of either one or two terminals with a capsaicin-like current produced similar depolarization measured before the bifurcation C, Activation of two terminals led to substantially higher depolarization (red) after the converging point than activation of only one terminal (blue). The AP firing following activation of two terminals, shown in A, is superimposed with the voltage traces to show that the depolarization evoked by the activation of two terminals remained high also at the time after the refractory period of the AP. The red shadowed area outlines the refractory period (49 ms), and the gray shadowed area outlines the time of the summated post-AP depolarization.