Pain and hyperalgesia occured when L 5 and L 6 spinal nerves were ligated. To ev aluate the electrophysiological changes that contribute to this sensory patholog y

whole cell current clamp recording was performed in DRGs that was obtained from neuropathic pain and control rats. After nerve ligation

action potential threshold reduced (more negative) in b oth small and median sized DRG neurons (-18.98±0.69 mV vs -11.12±1.06 mV in c ontrol small sized neurons; -19.44 ±2.22 mV vs -14.55±1.81 mV in control m edi an sized neurons)

but resting membrane potential action potential duration at half amplitude (APD 1/2 ) and action potential amplitude did not change sign ifica ntly. In addition

obvious membrane potential oscillations were observed in smal l sized DRG neurons from neuropathic pain rats (P<0.05 compared with control group). These results suggested that neuropathic pain increased the exci tability of nociceptors

which may be an important mechanism underlying peripher al hypersensitivity.