The Research On Ropivacaine Affect GABA-activatrd Membrane Current

Object: To investigate the effects of ropivavaine on GABA-activated currents in isolateddorsal root ganglion neurons in rats with neuropathic pain and discuss the analgesiamechanism of ropivacaine.Methods: The neuropathic pain model was established by chronic constriction injury(CCI).The rat DRG neurons were enzymatically dissociated. Whole-cell patch clamp technique wasused to record to the modulatory effects of ropivacaine on GABA-activated currents. Thechanges of currents of injured side and opposite side were expected to compare with controlgroup.Results:(1) The currents of injured side of CCI group were notablely decreased comparedwith control group(GABA concentration,0.1-1000μmol/L)（p<0.05）.(2) Different concentrations of ropivacaine (0.1-1000μmol/L) in most (65.7%,48/73) DRGneurons can produce amplitude in0~380pA with concentration dependent inward currents.(3) By the contrast, opposite side currents of CCI group increased significantly compared withinjured side and control group (GABA concentration,0.1-1000μmol/L)（p<0.05）.(4) The perfusion of10μ mol/L ropivacaine from CCI rat model operated side group makesthe dose-effect curve of DRG neurons of GABA (0.1-1000μ mol/L) activated currents to theleft, two EC50were11.18μmol/L and16.36μmol/L (n=18) had no significant differencebetween them (P>0.05).(5) Selected in0(not a perfusion),10,20,30,40s ropivacaine (10μmol/L) to GABA (100μmol/L) enhanced activation of membrane current with the perfusion time increased,30s isthe most obvious increase of GABA mediated membrane current action (n=15).(6) Pre-perfusion ropivacaine (0.1-1000μmol/L) to the three groups of DRG neurons,100μmol/L GABA activated currents in DRG neurons showed varying degrees of enhancement,and the GABA-activated currents of CCI opposite side group was significantly greater thanCCI injured side group and control group.（p<0.05）.Conclusion： The data indicates that the chronic constriction injury both change the functionof GABAAreceptors of injury side and opposite side. The decrease of pre-synaptic inhibitionof GABA may be the possible reason of anesthesia and analgesia of ropivacaine.