Objectives. In order to elucidate the influence of sympathetic nerves on
lumbar radiculopathy, we investigated whether sympathectomy attenuated
pain behaviour and altered the electrical properties of the dorsal
root ganglion (DRG) neurons in a rat model of lumbar root constriction. Methods. Sprague-Dawley rats were divided into three experimental groups.
In the root constriction group, the left L5 spinal nerve root was
ligated proximal to the DRG as a lumbar radiculopathy model. In
the root constriction + sympathectomy group, sympathectomy was performed
after the root constriction procedure. In the control group, no
procedures were performed. In order to evaluate the pain relief
effect of sympathectomy, behavioural analysis using mechanical and
thermal stimulation was performed. In order to evaluate the excitability
of the DRG neurons, we recorded action potentials of the isolated
single DRG neuron by the whole-cell patch-clamp method. Results. In behavioural analysis, sympathectomy attenuated the mechanical
allodynia and thermal hyperalgesia caused by lumbar root constriction.
In electrophysiological analysis, single isolated DRG neurons with
root constriction exhibited lower threshold current, more depolarised
resting membrane potential, prolonged action potential duration,
and more depolarisation frequency. These hyperexcitable alterations
caused by root constriction were significantly attenuated in rats
treated with surgical sympathectomy. Conclusion. The present results suggest that sympathectomy attenuates lumbar
radicular pain resulting from root constriction by altering the
electrical property of the DRG neuron itself. Thus, the sympathetic
nervous system was closely associated with
