Fig. 6. Schematic diagram of reduced Ca²⁺current (I^Ca) contribution to neuropathic pain. Injured nerve tissue distal to the spinal nerve ligation (SNL) undergoes wallerian degeneration (  dotted line ), while neurons from the L5 dorsal root ganglion (DRG) are activated by movement, catecholamines, other algogenic agents and cross-excitation from adjacent intact neurons. Reduced I^Cain Aα/Aβ and Aδ fibers shortens afterhyperpolarizations (AHPs), which contributes to burst firing. Loss of I^Caimpairs natural signal filtering at the T-branch, where the stem axon splits into spinal nerve and dorsal root branches. Reduced I^Caalso prolongs action potential (AP) duration, which may increase excitatory synaptic transmission in the dorsal horn (DH). Spared nerves transmit activity evoked by stimulation in the receptive field, and these signals encounter DH neurons that are sensitized by L5 input. L4, L5 = neurons in the fourth and fifth lumbar ganglia.