Changes in the action potential in sensory neurones after peripheral axotomy in vivo

FOLLOWING nerve injury, modified somatic ion channels may underlie ectopic activity in axotomized A-type neurones in dorsal root ganglia (DRGs) leadin g to abnormal pain signalling. Using intracellular microelectrodes both in vivo and in vitro, action potentials (APs) were recorded in rat DRG neurone s classified by axonal conduction velocity. After lesions to L5 spinal or s ciatic nerves, APs in both A alpha/beta and A delta cells were wider, and t hose in A alpha/beta neurones more frequently showed inflections during rep olarization, than APs in cells in undamaged ganglia. AP amplitudes and dV/d t(max) were not significantly altered by axotomy. These results confirm pre vious observations in intact ganglia in vitro but differ from those reporte d for dissociated neurones using patch recording techniques. (C) 1999 Lippi ncott Williams & Wilkins.