Electrophysiological properties in dorsal root ganglion neurons in lumbar radiculopathy model

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In the present study, we established a rat model with constriction of the proximal site of the DRG. The action potential and Na^<+-> K^+ current properties of DRG neurons in the rat model of lumbar radiculopathy are compared with sham-operated rats through the use of whole-cell patch clamp recordings.The rats in the root constriction group demonstrated statistically significant increase in tactile sensitivity, and higher thermal sensitivity than those in the sham operated and control groups up to 28 days after surgery. In measurement of the action potential in DRG neurons, significant changes were found in the threshold current, resting membrane potential, afterhyperpolarization, and APD50 of the neurons from the root constriction group. Excitability of DRG neurons was also evaluated by examining the discharge patterns in response to prolonged current injection. The incidence of sustained burst was significantly higher in root constriction neurons than in sham-operated neurons. In measurement of the membrane current, the Na^+ current in root constriction neurons was markedly larger than that in sham-operated neurons. There were no significant differences in K^+ current density and voltage dependency. Increased DRG excitability after root constriction could be a result of an increase in either the extent or available of Na^+ channels. Lumbar radicular pain may be caused by these changes in, Na^+ channel expression, and current properties.