Background Parvalbumin （PV）, as a mobile endogenous calcium buffer, plays an important role in affecting temporospatial characteristics of calcium transients and in modulating calcium homeostasis. PV is expressed in neurons in the dorsal root ganglion （DRG） and spinal dorsal horn and may be involved in synaptic transmission through regulating cytoplasm calcium concentrations. But the exact role of PV in peripheral sensory neurons remains unknown.Microtubule-associated protein 2 （MAP-2）, belonging to structural microtubule-associated protein family, is especially vulnerable to acute central nervous system （CNS） injury, and there will be rapid loss of MAP-2 at the injury site. The present study investigated the changes of PV expressing neurons and the MAP-2 neurons in the DRG after an operation for chronic constriction injury to the unilateral sciatic nerve （CCI-SN）, in order to demonstrate the possible roles of PV and MAP-2 in transmission and modulation of peripheral nociceptive information.Methods Seventy-two adult male Sprague-Dawley （SD） rats, weighing 180-220 g, were randomly divided into two groups （36 rats in each group）, the sham operation group and chronic constriction injury （CCI） group. Six rats in each group were randomly selected to receive mechanical and thermal sensitivity tests at one day before operation and 1,3, 5,7, and 14 days after surgery. After pain behavioral test, ipsilateral lumbar fifth DRGs were removed and double immunofluorescence staining was performed to assess the expression changes of PV and of MAP2 expressing neurons in the L5 DRG before or after surgery.Results The animals with CCI-SN showed obvious mechanical allodynia and thermal hyperalgesia （P＜0.05）. Both the thermal and mechanical hyperalgesia decreased to their lowest degree at 7 days after surgery compared to the baseline before surgery （P＜0.01）. In normal rats before surgery, a large number of neurons were MAP-2 single labeled cells, and just a small number of PV-expressed neur
