Study Of The Neurophysiological Mechanisms Of Chronic Pain

The peripheral nerve injury caused by some pathological factors results in pathological chronic pain, such as hyperalgesia, allodynia, and spontaneous pain ect. It was suggested that the ectopic discharges from the injured A- and C-fibers were the primary factors that is responsible for the chronic pain. The generation of the ectopic discharges is dependent on the ectopic developed K⁺, Na⁺,Ca²⁺ channels on the injured neurons, in which Ca²⁺ channel is thought to play a very key role. NE released from the post-ganglionic sympathetic fibers is thought an initiative agent to evoke these discharges, via adrenergic α₂ receptor mechanism. Clinically, the chronic painful symptoms such as hyperalgesia and allodynia in some patients can be alleviated by sympathetomy chemically or surgically. A similar results are also obtained in the animal model or the neuropathic pain Recently, morphological studies found that there were some sympathetic sproutings in the proximal of the injured nerve and its DRG in both neuroma model and tight ligation of the partial spinal nerves composed of sciatic nerve, and sometimes these sproutings surrounded around some large diameter nrueons to make sympathetic rings or plexus which might be the morphological basis of the functional relation between the sympathetic nerve and the primary sensory neurons. The CCI model of Bennett and Xie is one kind of animal model which demonstrated the chronic painful symptoms like those seen in patients. In this study, the techniques of the single fiber recording, extracellular microelectrode recording and measurement of animal behaviour were used to estimate the functional changes in the injured nerve, we have recorded the abnormal electrical activities of the injured nerve and have analyzed the effects of the drugs of ion channels and blocker of NE receptors apolied locally to the injured region and the DRG on the ectopic discharges, and the effect of the drug ion channel applied systemically by i.v. or i.p. on the abnormal discharges and the painful behaviour of the CCI model rats in order to analyze the relation between the newly developed ion channels and the ectopic discharges and search for the threshold effective concentration of the antagonist...