Electrophysiological changes in dorsal root ganglion neurons lumbar radiculopathy rat

Abstract

Enhanced excitation of primary afferent neuron is well known in peripheral nerve injury. On the other hand, pathomechanisms of lumbar radiculopathy is still unclear. Therefore, we investigated the electrical properties of dorsal root ganglion neurons in lumbar radiculopathy rat in use of whole-cell patch clamp recordings. Left L5 spinal root of male Sprague-Dawley rats was ligated tightly in lumbar root constriction group. To compare the excitability of DRG neurons from root constriction and sham operated rats, we recorded action potentials of the neurons. Repetitive discharge of action potential was observed by application of long pulse of current injection (1000ms). Root constriction group exhibited decreased threshold current, more depolarized resting membrane potential, and longer duration of action potential. Most of sham group DRG neurons (85%) exhibited single spike by the long current injection. In contrast, 60% of root constriction group DRG neurons exhibited multiple spike pattern. The incidence of multiple spike pattern was significantly higher in root constriction neurons than in sham neurons. Enhanced excitation of DRG neurons observed in the present study was similar to that in peripheral nerve injury model. [Jpn J Physiol 54 Suppl:S170 (2004)]