Change in calcium currents in isolated dorsal root ganglion neurons in rats with neuropathic pain

Objective To examine the changes in calcium currents in isolated dorsal root ganglion (DRG) neurons in rats with neuropathic pain.Methods The neuropathic pain model was established by modified spinal nerve ligation (SNL) 2 to 4 weeks before electrophysiologic recording. The rat DRG neurons were enzymatically dissociated. Whole -cell patch clamp technique was used to record Ca2+ current.Results In large DRG neurons the mean peak value of electric current-voltage ( Ⅰ - Ⅴ) curve was decreased significantly from ( - 105±13) pA/ pF in control group ( n = 9) to ( - 66±10) pA/pF in neuropathic pain group ( n = 11) (P 0.05). The V1/2 of fast phase inactivation curve was shifted from ( -45.8±0.8) mV in control group ( n = 9) to (-41.8±0.3) mV in neuropathic pain group ( n = 11) ( P 0.05). There was no difference in activation curves between the two groups ( P 0.05) . Conclusion In neuropathic rat Ca2+ currents in large DRG neurons are decreased and the voltage dependence of the fast component of inactivation is shifted to more depolarized potentials. These changes may contribute to hyperalgesia and allodynia of neuropathic pain.