Figure 8.

The Ra of the terminal branch's conductive part determines the nociceptive gain. A, upper, Scheme of the stimulated terminal branch with the location of the recording pipette 2.5 µm before the SIZ. The Nav conductances at the conductive part were annulled to prevent the effect of the APs on the measurements of the terminal membrane potential. Lower, Heatmap representing the relation between the Ra of the conductive part (Ra), the conductive part length, and the depolarization of the terminal membrane recorded at the Nav-less part, 2.5 µm before the SIZ. The resulted membrane potential is color coded (shown on the right). Note that when the Ra of the conductive part is similar to the Ra of the proximal fiber (1 × Ra), the depolarization resulted from the application of a capsaicin-like current to the terminal tip is substantially lower than when Ra is higher. B, Same as A, but the recordings are performed at the SIZ. C, The relation between the Ra of the conductive part (Ra), the conductive part length, and the AP firing measured at the central terminal following stimulation of a single terminal. The Nav conductance of the conductive part is intact. The AP count is color coded (shown on the right).