Involvement Of CIC-3in The Regulatory Effect On Neuropathic Pain In The Spinal Dorsal Horn And Dorsal Root Ganglion Of The Rat

Voltage-gated chloride channel type3(ClC-3) is a wide distributed chloridechannel in vivo, which has been studied widely. ClC-3related to the regulationof variety of physiological functions, such as cell volume, intracellularacidification, as well as some pathological processes like tumor metastasis andepilepsy, etc. ClC-3is widely distributed in human body, mainly in themyocardium, bronchial epithelium, retina and some tumor cells. In nervoussystem, it mainly located in synapses. The activation of chloride channels showsobvious analgesic effect. Intrathecal administration of the chloride channelagonist GANA significantly interfere the process of chronic pain.5-nitro-2-(3-phenylpropyl-amino)benzoicacid (NPPB) is a efficient andselective chloride channel blocker, which has been particularly useful for thestudy of anion channels in vivo and in vitro.Neuropathic pain caused by nerve injury is a common clinical etiology inchronic pain. It caused a great pain to patients and is difficult for treatment. Therefore, exploring its pathogenesis will help us identify therapeutic targetsand ease pain of patients. Activation or down regulation of ion channel playdifferent roles in the modulation of neuropathic pain. Previous studies havefocused on cation channels, such asNaV1.7, NaV1.8and CaV1.2, instead of theanion channel. The chloridion is one of the most abundant anions in vivo, whichplays a very important role in regulating the excitability of nervous system.ClC-3regulates the concentration of chloridion in neuron, which has importanteffect in tumor metastasis, epilepsy and other diseases. But the effect of ClC-3in neuropathic pain remains obscure. In this study, by using common peronealnerve (CPN) ligation neuropathic pain modelwe applied the chloride channelblocker5-nitro-2,3-(phenylpropylamino)-benzoic acid (NPPB) to test theeffect of NPPB on the immunohistochemistry changes of ClC-3and thebehavioral responses of animals with neuropathic pain.1. The expression of ClC-3in spinal cord dorsal horn and dorsal rootganglia in rat of neuropathic painBy using immunohistochemical staining, it was found that in control rat,ClC-3immunoreactivity (IR) was mainly distributed in the superficial layers ofspinal cord dorsal horn, especially in the layer I; In DRG, ClC-3-IR wasdistributed in the neurons’ membrane. Seven days after CPN ligation, theexpression of ClC-3in the DRG and spinal cord dorsal horn was up-regulated.With the progresses of chronic pain, the expression of ClC-3was decreasedgradually. Those results were confirmed by western blot and prompted that inCPN ligation-induced neuropathic pain, ClC-3plays different role in differentphase. 2. The effect to pain behavior after blocking ClC-3After intrathecal administration of chloridion channel blockers NPPB (5μl),we used von Frey filaments and Hargreaves method to detected MWT and TWL.We found that the rats with NPPB intrathecal administration have lower MWTand TWL, compare with those with DMSO intrathecal administration. Thiseffect is most obvious in7days after CPN ligation.Above results indicated that in normal rat, ClC-3is mainly distributed in theDRG neurons and the superficial layers of spinal cord dorsal horn. In theneuropathic pain model rat, ClC-3is increased in early stage and decreased inadvanced stage. Intrathecal administration NPPB can decrease mechanical andheat pain threshold. These results have proved role of ClC-3in neuropathic painin morphology and behavior.