Axotomy affects calcium-sensitive potassium conductance in sympathetic neurones

Following peripheral nerve section, the cell body and proximal axon undergo various physiological and morphological changes which may be associated with regrowth. We found that axotomy reduced the amplitude and duration of the afterhyperpolarization (AHP) of the action potential (AP) of bullfrog sympathetic neurones. In addition, the repolarization of the AP was slowed. The Ca²⁺-channel blocker, Cd²⁺ (200 μM) produced similar effects in normal cells by blocking the Ca²⁺-sensitive K⁺ conductances (g_{k, Ca}) which contribute to the AHP and to AP repolarization. Although Ca²⁺-channel function was preserved after axotomy, Cd²⁺ did not affect axotomized neurones. This suggests that axotomy promotes a functional loss of g_{k, Ca} which could reflect a regenerative response of the cell to injury.